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diff --git a/specs/CH07.xml b/specs/CH07.xml new file mode 100644 index 0000000..7ea7259 --- /dev/null +++ b/specs/CH07.xml @@ -0,0 +1,4989 @@ +<chapter id='Event_Management'> +<title>Event Management</title> +<para> +While Xlib allows the reading and processing of events anywhere in an application, +widgets in the X Toolkit neither directly read events +nor grab the server or pointer. +Widgets register procedures that are to be called +when an event or class of events occurs in that widget. +</para> + +<para> +A typical application consists of startup code followed by an event loop +that reads events and dispatches them by calling +the procedures that widgets have registered. +The default event loop provided by the Intrinsics is +<xref linkend='XtAppMainLoop' xrefstyle='select: title'/>. +</para> + +<para> +The event manager is a collection of functions to perform the following tasks: +</para> +<itemizedlist spacing='compact'> + <listitem> + <para> +Add or remove event sources other than X server events (in particular, +timer interrupts, file input, or POSIX signals). + </para> + </listitem> + <listitem> + <para> +Query the status of event sources. + </para> + </listitem> + <listitem> + <para> +Add or remove procedures to be called when an event occurs for a particular +widget. + </para> + </listitem> + <listitem> + <para> +Enable and +disable the dispatching of user-initiated events (keyboard and pointer events) +for a particular widget. + </para> + </listitem> + <listitem> + <para> +Constrain the dispatching of events to a cascade of pop-up widgets. + </para> + </listitem> + <listitem> + <para> +Register procedures to be called when specific events arrive. + </para> + </listitem> + <listitem> + <para> +Register procedures to be called when the Intrinsics will block. + </para> + </listitem> + <listitem> + <para> +Enable safe operation in a multi-threaded environment. + </para> + </listitem> +</itemizedlist> +<para> +Most widgets do not need to call any of the event handler functions explicitly. +The normal interface to X events is through the higher-level +translation manager, +which maps sequences of X events, with modifiers, into procedure calls. +Applications rarely use any of the event manager routines besides +<xref linkend='XtAppMainLoop' xrefstyle='select: title'/>. +</para> +<sect1 id="Adding_and_Deleting_Additional_Event_Sources"> +<title>Adding and Deleting Additional Event Sources</title> +<para> +While most applications are driven only by X events, +some applications need to incorporate other sources of input +into the Intrinsics event-handling mechanism. +The event manager provides routines to integrate notification of timer events +and file data pending into this mechanism. +</para> + +<para> +The next section describes functions that provide input gathering from files. +The application registers the files with the Intrinsics read routine. +When input is pending on one of the files, +the registered callback procedures are invoked. +</para> +<sect2 id="Adding_and_Removing_Input_Sources"> +<title>Adding and Removing Input Sources</title> +<para> +To register a new file as an input source for a given application context, use +<xref linkend='XtAppAddInput' xrefstyle='select: title'/>. +</para> + +<funcsynopsis id='XtAppAddInput'> +<funcprototype> +<funcdef>XtInputId <function>XtAppAddInput</function></funcdef> + <paramdef>XtAppContext <parameter>app_context</parameter></paramdef> + <paramdef>int <parameter>source</parameter></paramdef> + <paramdef>XtPointer <parameter>condition</parameter></paramdef> + <paramdef>XtInputCallbackProc <parameter>proc</parameter></paramdef> + <paramdef>XtPointer <parameter>client_data</parameter></paramdef> +</funcprototype> +</funcsynopsis> + +<variablelist> + <varlistentry> + <term> + <emphasis remap='I'>app_context</emphasis> + </term> + <listitem> + <para> +Specifies the application context that identifies the application. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>source</emphasis> + </term> + <listitem> + <para> +Specifies the source file descriptor on a POSIX-based system +or other operating-system-dependent device specification. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>condition</emphasis> + </term> + <listitem> + <para> +Specifies the mask that indicates a read, write, or exception condition +or some other operating-system-dependent condition. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>proc</emphasis> + </term> + <listitem> + <para> +Specifies the procedure to be called when the condition is found. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>client_data</emphasis> + </term> + <listitem> + <para> +Specifies an argument passed to the specified procedure +when it is called. + </para> + </listitem> + </varlistentry> +</variablelist> + +<para> +The +<xref linkend='XtAppAddInput' xrefstyle='select: title'/> +function registers with the Intrinsics read routine a new source of events, +which is usually file input but can also be file output. +Note that <emphasis remap='I'>file</emphasis> should be loosely interpreted to mean any sink +or source of data. +<xref linkend='XtAppAddInput' xrefstyle='select: title'/> +also specifies the conditions under which the source can generate events. +When an event is pending on this source, +the callback procedure is called. +</para> + +<para> +The legal values for the <emphasis remap='I'>condition</emphasis> argument are operating-system-dependent. +On a POSIX-based system, +<emphasis remap='I'>source</emphasis> is a file number and the condition is some union of the following: +<variablelist> + <varlistentry> + <term> + <emphasis role='strong'>XtInputReadMask</emphasis> + </term> + <listitem> + <para> +Specifies that <emphasis remap='I'>proc</emphasis> is to be called when <emphasis remap='I'>source</emphasis> has data to be read. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis role='strong'>XtInputWriteMask</emphasis> + </term> + <listitem> + <para> +Specifies that <emphasis remap='I'>proc</emphasis> is to be called when <emphasis remap='I'>source</emphasis> is ready +for writing. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis role='strong'>XtInputExceptMask</emphasis> + </term> + <listitem> + <para> +Specifies that <emphasis remap='I'>proc</emphasis> is to be called when <emphasis remap='I'>source</emphasis> has +exception data. + </para> + </listitem> + </varlistentry> +</variablelist> +</para> + +<para> +Callback procedure pointers used to handle file events are of +type +<xref linkend='XtInputCallbackProc' xrefstyle='select: title'/>. +</para> + +<funcsynopsis id='XtInputCallbackProc'> +<funcprototype> +<funcdef>typedef void <function>(*XtInputCallbackProc)</function></funcdef> + <paramdef>XtPointer <parameter>client_data</parameter></paramdef> + <paramdef>int *<parameter>source</parameter></paramdef> + <paramdef>XtInputId *<parameter>id</parameter></paramdef> +</funcprototype> +</funcsynopsis> + +<variablelist> + <varlistentry> + <term> + <emphasis remap='I'>client_data</emphasis> + </term> + <listitem> + <para> +Passes the client data argument that was registered for this procedure in +<function>XtApp\%AddInput</function>. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>source</emphasis> + </term> + <listitem> + <para> +Passes the source file descriptor generating the event. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>id</emphasis> + </term> + <listitem> + <para> +Passes the id returned from the corresponding +<xref linkend='XtAppAddInput' xrefstyle='select: title'/> +call. + </para> + </listitem> + </varlistentry> +</variablelist> + +<para> +See <xref linkend='Using_the_Intrinsics_in_a_Multi_Threaded_Environment' /> +for information regarding the use of +<xref linkend='XtAppAddInput' xrefstyle='select: title'/> +in multiple threads. +</para> + +<para> +To discontinue a source of input, use +<xref linkend='XtRemoveInput' xrefstyle='select: title'/>. +</para> + +<funcsynopsis id='XtRemoveInput'> +<funcprototype> +<funcdef>void <function>XtRemoveInput</function></funcdef> + <paramdef>XtInputId <parameter>id</parameter></paramdef> +</funcprototype> +</funcsynopsis> + +<variablelist> + <varlistentry> + <term> + <emphasis remap='I'>id</emphasis> + </term> + <listitem> + <para> +Specifies the id returned from the corresponding +<xref linkend='XtAppAddInput' xrefstyle='select: title'/> +call. + </para> + </listitem> + </varlistentry> +</variablelist> + +<para> +The +<xref linkend='XtRemoveInput' xrefstyle='select: title'/> +function causes the Intrinsics read routine to stop watching for events +from the file source specified by <emphasis remap='I'>id</emphasis>. +</para> + +<para> +See <xref linkend='Using_the_Intrinsics_in_a_Multi_Threaded_Environment' /> +for information regarding the use of +<xref linkend='XtRemoveInput' xrefstyle='select: title'/> +in multiple threads. +</para> +</sect2> + +<sect2 id="Adding_and_Removing_Blocking_Notifications"> +<title>Adding and Removing Blocking Notifications</title> +<para> +Occasionally it is desirable for an application to receive notification +when the Intrinsics event manager detects no pending input from file sources +and no pending input from X server event sources and is about to block +in an operating system call. +</para> + +<para> +To register a hook that is called immediately prior to event blocking, use +<xref linkend='XtAppAddBlockHook' xrefstyle='select: title'/>. +</para> + +<funcsynopsis id='XtAppAddBlockHook'> +<funcprototype> +<funcdef>XtBlockHookId <function>XtAppAddBlockHook</function></funcdef> + <paramdef>XtAppContext <parameter>app_context</parameter></paramdef> + <paramdef>XtBlockHookProc <parameter>proc</parameter></paramdef> + <paramdef>XtPointer <parameter>client_data</parameter></paramdef> +</funcprototype> +</funcsynopsis> + +<variablelist> + <varlistentry> + <term> + <emphasis remap='I'>app_context</emphasis> + </term> + <listitem> + <para> +Specifies the application context that identifies the application. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>proc</emphasis> + </term> + <listitem> + <para> +Specifies the procedure to be called before blocking. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>client_data</emphasis> + </term> + <listitem> + <para> +Specifies an argument passed to the specified procedure when it is called. + </para> + </listitem> + </varlistentry> +</variablelist> + +<para> +The +<xref linkend='XtAppAddBlockHook' xrefstyle='select: title'/> +function registers the specified procedure and returns an identifier for it. +The hook procedure <emphasis remap='I'>proc</emphasis> is called at any time in the future when +the Intrinsics are about to block pending some input. +</para> + +<para> +The procedure pointers used to provide notification of event blocking +are of type +<xref linkend='XtBlockHookProc' xrefstyle='select: title'/>. +</para> + +<funcsynopsis id='XtBlockHookProc'> +<funcprototype> +<funcdef>void <function>*XtBlockHookProc</function></funcdef> + <paramdef>XtPointer <parameter>client_data</parameter></paramdef> +</funcprototype> +</funcsynopsis> + +<variablelist> + <varlistentry> + <term> + <emphasis remap='I'>client_data</emphasis> + </term> + <listitem> + <para> +Passes the client data argument that was registered for this procedure in +<function>XtApp\%AddBlockHook</function>. + </para> + </listitem> + </varlistentry> +</variablelist> + +<para> +To discontinue the use of a procedure for blocking notification, use +<xref linkend='XtRemoveBlockHook' xrefstyle='select: title'/>. +</para> + +<funcsynopsis id='XtRemoveBlockHook'> +<funcprototype> +<funcdef>void <function>XtRemoveBlockHook</function></funcdef> + <paramdef>XtBlockHookId <parameter>id</parameter></paramdef> +</funcprototype> +</funcsynopsis> + +<variablelist> + <varlistentry> + <term> + <emphasis remap='I'>id</emphasis> + </term> + <listitem> + <para> +Specifies the identifier returned from the corresponding call to +<xref linkend='XtAppAddBlockHook' xrefstyle='select: title'/>. + </para> + </listitem> + </varlistentry> +</variablelist> + +<para> +The +<xref linkend='XtRemoveBlockHook' xrefstyle='select: title'/> +function removes the specified procedure from the list of procedures +that are called by the Intrinsics read routine before blocking on event sources. +</para> +</sect2> + +<sect2 id="Adding_and_Removing_Timeouts"> +<title>Adding and Removing Timeouts</title> +<para> +The timeout facility notifies the application or the widget +through a callback procedure that a specified time interval has elapsed. +Timeout values are uniquely identified by an interval id. +</para> + +<para> +To register a timeout callback, use +<xref linkend='XtAppAddTimeOut' xrefstyle='select: title'/>. +</para> + +<funcsynopsis id='XtAppAddTimeOut'> +<funcprototype> +<funcdef>XtIntervalId <function>XtAppAddTimeOut</function></funcdef> + <paramdef>XtAppContext <parameter>app_context</parameter></paramdef> + <paramdef>unsigned long <parameter>interval</parameter></paramdef> + <paramdef>XtTimerCallbackProc <parameter>proc</parameter></paramdef> + <paramdef>XtPointer <parameter>client_data</parameter></paramdef> +</funcprototype> +</funcsynopsis> + +<variablelist> + <varlistentry> + <term> + <emphasis remap='I'>app_context</emphasis> + </term> + <listitem> + <para> +Specifies the application context for which the timer is to be set. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>interval</emphasis> + </term> + <listitem> + <para> +Specifies the time interval in milliseconds. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>proc</emphasis> + </term> + <listitem> + <para> +Specifies the procedure to be called when the time expires. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>client_data</emphasis> + </term> + <listitem> + <para> +Specifies an argument passed to the specified procedure +when it is called. + </para> + </listitem> + </varlistentry> +</variablelist> + +<para> +The +<xref linkend='XtAppAddTimeOut' xrefstyle='select: title'/> +function creates a timeout and returns an identifier for it. +The timeout value is set to <emphasis remap='I'>interval</emphasis>. +The callback procedure <emphasis remap='I'>proc</emphasis> is called when +<xref linkend='XtAppNextEvent' xrefstyle='select: title'/> +or +<xref linkend='XtAppProcessEvent' xrefstyle='select: title'/> +is next called after the time interval elapses, +and then the timeout is removed. +</para> + +<para> +Callback procedure pointers used with timeouts are of +type +<xref linkend='XtTimerCallbackProc' xrefstyle='select: title'/>. +</para> + +<funcsynopsis id='XtTimerCallbackProc'> +<funcprototype> +<funcdef>void <function>*XtTimerCallbackProc</function></funcdef> + <paramdef>XtPointer <parameter>client_data</parameter></paramdef> + <paramdef>XtIntervalId *<parameter>timer</parameter></paramdef> +</funcprototype> +</funcsynopsis> + +<variablelist> + <varlistentry> + <term> + <emphasis remap='I'>client_data</emphasis> + </term> + <listitem> + <para> +Passes the client data argument that was registered for this procedure in +<function>XtApp\%AddTimeOut</function>. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>timer</emphasis> + </term> + <listitem> + <para> +Passes the id returned from the corresponding +<xref linkend='XtAppAddTimeOut' xrefstyle='select: title'/> +call. + </para> + </listitem> + </varlistentry> +</variablelist> + +<para> +See <xref linkend='Using_the_Intrinsics_in_a_Multi_Threaded_Environment' /> +for information regarding the use of +<xref linkend='XtAppAddTimeOut' xrefstyle='select: title'/> +in multiple threads. +</para> + +<para> +To clear a timeout value, use +<xref linkend='XtRemoveTimeOut' xrefstyle='select: title'/>. +</para> + +<funcsynopsis id='XtRemoveTimeOut'> +<funcprototype> +<funcdef>void <function>XtRemoveTimeOut</function></funcdef> + <paramdef>XtIntervalId <parameter>timer</parameter></paramdef> +</funcprototype> +</funcsynopsis> + +<variablelist> + <varlistentry> + <term> + <emphasis remap='I'>timer</emphasis> + </term> + <listitem> + <para> +Specifies the id for the timeout request to be cleared. + </para> + </listitem> + </varlistentry> +</variablelist> + +<para> +The +<xref linkend='XtRemoveTimeOut' xrefstyle='select: title'/> +function removes the pending timeout. +Note that timeouts are automatically removed once they trigger. +</para> + +<para> +Please refer to Section 7.12 for information regarding the use of +<xref linkend='XtRemoveTimeOut' xrefstyle='select: title'/> +in multiple threads. +</para> +</sect2> + +<sect2 id="Adding_and_Removing_Signal_Callbacks"> +<title>Adding and Removing Signal Callbacks</title> +<para> +The signal facility notifies the application or the widget through a +callback procedure that a signal or other external asynchronous event +has occurred. The registered callback procedures are uniquely identified +by a signal id. +</para> + +<para> +Prior to establishing a signal handler, the application or widget should +call +<xref linkend='XtAppAddSignal' xrefstyle='select: title'/> +and store the resulting identifier in a place accessible to the signal +handler. When a signal arrives, the signal handler should call +<xref linkend='XtNoticeSignal' xrefstyle='select: title'/> +to notify the Intrinsics that a signal has occured. To register a signal +callback use +<xref linkend='XtAppAddSignal' xrefstyle='select: title'/>. +</para> + +<funcsynopsis id='XtAppAddSignal'> +<funcprototype> +<funcdef>XtSignalId <function>XtAppAddSignal</function></funcdef> + <paramdef>XtAppContext <parameter>app_context</parameter></paramdef> + <paramdef>XtSignalCallbackProc <parameter>proc</parameter></paramdef> + <paramdef>XtPointer <parameter>client_data</parameter></paramdef> +</funcprototype> +</funcsynopsis> + +<variablelist> + <varlistentry> + <term> + <emphasis remap='I'>app_context</emphasis> + </term> + <listitem> + <para> +Specifies the application context that identifies the application. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>proc</emphasis> + </term> + <listitem> + <para> +Specifies the procedure to be called when the signal is noticed. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>client_data</emphasis> + </term> + <listitem> + <para> +Specifies an argument passed to the specified procedure when it is called. + </para> + </listitem> + </varlistentry> +</variablelist> + +<para> +The callback procedure pointers used to handle signal events are of type +<xref linkend='XtSignalCallbackProc' xrefstyle='select: title'/>. +</para> + +<funcsynopsis id='XtSignalCallbackProc'> +<funcprototype> +<funcdef>typedef void <function>(*XtSignalCallbackProc)</function></funcdef> + <paramdef>XtPointer <parameter>client_data</parameter></paramdef> + <paramdef>XtSignalId *<parameter>id</parameter></paramdef> +</funcprototype> +</funcsynopsis> + +<variablelist> + <varlistentry> + <term> + <emphasis remap='I'>client_data</emphasis> + </term> + <listitem> + <para> +Passes the client data argument that was registered for this procedure in +<xref linkend='XtAppAddSignal' xrefstyle='select: title'/>. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>id</emphasis> + </term> + <listitem> + <para> +Passes the id returned from the corresponding +<xref linkend='XtAppAddSignal' xrefstyle='select: title'/> +call. + </para> + </listitem> + </varlistentry> +</variablelist> + +<para> +To notify the Intrinsics that a signal has occured, use +<xref linkend='XtNoticeSignal' xrefstyle='select: title'/>. +</para> + +<funcsynopsis id='XtNoticeSignal'> +<funcprototype> +<funcdef>void <function>XtNoticeSignal</function></funcdef> + <paramdef>XtSignalId <parameter>id</parameter></paramdef> +</funcprototype> +</funcsynopsis> + +<variablelist> + <varlistentry> + <term> + <emphasis remap='I'>id</emphasis> + </term> + <listitem> + <para> +Specifies the id returned from the corresponding +<xref linkend='XtAppAddSignal' xrefstyle='select: title'/> +call. + </para> + </listitem> + </varlistentry> +</variablelist> + +<para> +On a POSIX-based system, +<xref linkend='XtNoticeSignal' xrefstyle='select: title'/> +is the only Intrinsics function that can safely be called from a signal handler. +If +<xref linkend='XtNoticeSignal' xrefstyle='select: title'/> +is invoked multiple times before the Intrinsics are able to invoke the +registered callback, the callback is only called once. +Logically, the Intrinsics maintain ``pending'' flag for each registered callback. +This flag is initially +<function>False</function> +and is set to +<function>True</function> +by +<xref linkend='XtNoticeSignal' xrefstyle='select: title'/>. +When +<xref linkend='XtAppNextEvent' xrefstyle='select: title'/> +or +<xref linkend='XtAppProcessEvent' xrefstyle='select: title'/> +(with a mask including +<function>XtIMSignal</function>) +is called, all registered callbacks with ``pending'' +<function>True</function> +are invoked and the flags are reset to +<function>False</function>. +</para> + +<para> +If the signal handler wants to track how many times the signal has been +raised, it can keep its own private counter. Typically the handler would +not do any other work; the callback does the actual processing for the +signal. The Intrinsics never block signals from being raised, so if a given +signal can be raised multiple times before the Intrinsics can invoke the +callback for that signal, the callback must be designed to deal with +this. In another case, a signal might be raised just after the Intrinsics +sets the pending flag to +<function>False</function> +but before the callback can get control, in which case the pending flag +will still be +<function>True</function> +after the callback returns, and the Intrinsics will invoke the callback +again, even though all of the signal raises have been handled. The +callback must also be prepared to handle this case. +</para> + +<para> +To remove a registered signal callback, call +<xref linkend='XtRemoveSignal' xrefstyle='select: title'/>. +</para> + +<funcsynopsis id='XtRemoveSignal'> +<funcprototype> +<funcdef>void <function>XtRemoveSignal</function></funcdef> + <paramdef>XtSignalId <parameter>id</parameter></paramdef> +</funcprototype> +</funcsynopsis> + +<variablelist> + <varlistentry> + <term> + <emphasis remap='I'>id</emphasis> + </term> + <listitem> + <para> +Specifies the id returned by the corresponding call to +<xref linkend='XtAppAddSignal' xrefstyle='select: title'/>. + </para> + </listitem> + </varlistentry> +</variablelist> + +<para> +The client should typically disable the source of the signal before calling +<xref linkend='XtRemoveSignal' xrefstyle='select: title'/>. +If the signal could have been raised again before the source was disabled +and the client wants to process it, then after disabling the source but +before calling +<xref linkend='XtRemoveSignal' xrefstyle='select: title'/> +the client can test for signals with +<xref linkend='XtAppPending' xrefstyle='select: title'/> +and process them by calling +<xref linkend='XtAppProcessEvent' xrefstyle='select: title'/> +with the mask +<function>XtIMSignal</function>. +</para> +</sect2> +</sect1> + +<sect1 id="Constraining_Events_to_a_Cascade_of_Widgets"> +<title>Constraining Events to a Cascade of Widgets</title> +<para> +Modal widgets are widgets that, except for the input directed to them, +lock out user input to the application. +</para> + +<para> +When a modal menu or modal dialog box is popped up using +<xref linkend='XtPopup' xrefstyle='select: title'/>, +user events (keyboard and pointer events) that occur outside the modal +widget should be delivered to the modal widget or ignored. +In no case will user events be delivered to a widget outside +the modal widget. +</para> + +<para> +Menus can pop up submenus, and dialog boxes can pop up further dialog +boxes to create a pop-up cascade. +In this case, +user events may be delivered to one of several modal widgets in the cascade. +</para> + +<para> +Display-related events should be delivered outside the modal cascade so that +exposure events and the like keep the application's display up-to-date. +Any event that occurs within the cascade is delivered as usual. +The user events delivered to the most recent spring-loaded shell +in the cascade when they occur outside the cascade are called remap events +and are +<function>KeyPress</function>, +<function>KeyRelease</function>, +<function>ButtonPress</function>, +and +<function>ButtonRelease</function>. +The user events ignored when they occur outside the cascade are +<function>MotionNotify</function> +and +<function>EnterNotify</function>. +All other events are delivered normally. +In particular, note that this is one +way in which widgets can receive +<function>LeaveNotify</function> +events without first receiving +<function>EnterNotify</function> +events; they should be prepared to deal with +this, typically by ignoring any unmatched +<function>LeaveNotify</function> +events. +</para> + +<para> +<xref linkend='XtPopup' xrefstyle='select: title'/> +uses the +<xref linkend='XtAddGrab' xrefstyle='select: title'/> +and +<xref linkend='XtRemoveGrab' xrefstyle='select: title'/> +functions to constrain user events to a modal cascade +and subsequently to remove a grab when the modal widget is popped down. +</para> + +<para> +To constrain or redirect user input to a modal widget, use +<xref linkend='XtAddGrab' xrefstyle='select: title'/>. +</para> + +<funcsynopsis id='XtAddGrab'> +<funcprototype> +<funcdef>void <function>XtAddGrab</function></funcdef> + <paramdef>Widget <parameter>w</parameter></paramdef> + <paramdef>Boolean <parameter>exclusive</parameter></paramdef> + <paramdef>Boolean <parameter>spring_loaded</parameter></paramdef> +</funcprototype> +</funcsynopsis> + +<variablelist> + <varlistentry> + <term> + <emphasis remap='I'>w</emphasis> + </term> + <listitem> + <para> +Specifies the widget to add to the modal cascade. Must be of class Core or any subclass thereof. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>exclusive</emphasis> + </term> + <listitem> + <para> +Specifies whether user events should be dispatched exclusively to this widget +or also to previous widgets in the cascade. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>spring_loaded</emphasis> + </term> + <listitem> + <para> +Specifies whether this widget was popped up because the user pressed +a pointer button. + </para> + </listitem> + </varlistentry> +</variablelist> + +<para> +The +<xref linkend='XtAddGrab' xrefstyle='select: title'/> +function appends the widget to the modal cascade +and checks that <emphasis remap='I'>exclusive</emphasis> is +<function>True</function> +if <emphasis remap='I'>spring_loaded</emphasis> is +<function>True</function>. +If this condition is not met, +<xref linkend='XtAddGrab' xrefstyle='select: title'/> +generates a warning message. +</para> + +<para> +The modal cascade is used by +<xref linkend='XtDispatchEvent' xrefstyle='select: title'/> +when it tries to dispatch a user event. +When at least one modal widget is in the widget cascade, +<xref linkend='XtDispatchEvent' xrefstyle='select: title'/> +first determines if the event should be delivered. +It starts at the most recent cascade entry and follows the cascade up to and +including the most recent cascade entry added with the <emphasis remap='I'>exclusive</emphasis> parameter +<function>True</function>. +</para> + +<para> +This subset of the modal cascade along with all descendants of these widgets +comprise the active subset. +User events that occur outside the widgets in this subset are ignored +or remapped. +Modal menus with submenus generally add a submenu widget to the cascade +with <emphasis remap='I'>exclusive</emphasis> +<function>False</function>. +Modal dialog boxes that need to restrict user input to the most deeply nested +dialog box add a subdialog widget to the cascade with <emphasis remap='I'>exclusive</emphasis> +<function>True</function>. +User events that occur within the active subset are delivered to the +appropriate widget, which is usually a child or further descendant of the modal +widget. +</para> + +<para> +Regardless of where in the application they occur, +remap events are always delivered to the most recent widget in the active +subset of the cascade registered with <emphasis remap='I'>spring_loaded</emphasis> +<function>True</function>, +if any such widget exists. +If the event +occurred in the active subset of the cascade but outside the +spring-loaded widget, it is delivered normally before being +delivered also to the spring-loaded widget. +Regardless of where it is dispatched, the Intrinsics do not modify +the contents of the event. +</para> + +<para> +To remove the redirection of user input to a modal widget, use +<xref linkend='XtRemoveGrab' xrefstyle='select: title'/>. +</para> + +<funcsynopsis id='XtRemoveGrab'> +<funcprototype> +<funcdef>void <function>XtRemoveGrab</function></funcdef> + <paramdef>Widget <parameter>w</parameter></paramdef> +</funcprototype> +</funcsynopsis> + +<variablelist> + <varlistentry> + <term> + <emphasis remap='I'>w</emphasis> + </term> + <listitem> + <para> +Specifies the widget to remove from the modal cascade. + </para> + </listitem> + </varlistentry> +</variablelist> + +<para> +The +<xref linkend='XtRemoveGrab' xrefstyle='select: title'/> +function removes widgets from the modal cascade starting +at the most recent widget up to and including the specified widget. +It issues a warning if the specified widget is not on the modal cascade. +</para> +<sect2 id="Requesting_Key_and_Button_Grabs"> +<title>Requesting Key and Button Grabs</title> +<para> +The Intrinsics provide a set of key and button grab interfaces that +are parallel to those provided by Xlib and that allow the Intrinsics +to modify event dispatching when necessary. X Toolkit applications and +widgets that need to passively grab keys or buttons or actively grab +the keyboard or pointer should use the +following Intrinsics routines rather than the corresponding Xlib +routines. +</para> + +<para> +To passively grab a single key of the keyboard, use +<xref linkend='XtGrabKey' xrefstyle='select: title'/>. +</para> + +<funcsynopsis id='XtGrabKey'> +<funcprototype> +<funcdef>void <function>XtGrabKey</function></funcdef> + <paramdef>Widget <parameter>widget</parameter></paramdef> + <paramdef>KeyCode <parameter>keycode</parameter></paramdef> + <paramdef>Modifiers <parameter>modifiers</parameter></paramdef> + <paramdef>Boolean <parameter>owner_events</parameter></paramdef> + <paramdef>int <parameter>pointer_mode</parameter></paramdef> +</funcprototype> +</funcsynopsis> + +<variablelist> + <varlistentry> + <term> + <emphasis remap='I'>widget</emphasis> + </term> + <listitem> + <para> +Specifies the widget in whose window the key is to be grabbed. Must be of class Core or any subclass thereof. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>keycode</emphasis> + </term> + <term> + <emphasis remap='I'>modifiers</emphasis> + </term> + <term> + <emphasis remap='I'>owner_events</emphasis> + </term> + <term> + <emphasis remap='I'>pointer_mode</emphasis> + </term> + <term> + <emphasis remap='I'>keyboard_mode</emphasis> + </term> + <listitem> + <para> +Specify arguments to +<function>XGrabKey</function>; +see <olink targetdoc='libX11' targetptr='Keyboard_Grabbing'>Section 12.2</olink> +in <olink targetdoc='libX11' targetptr='libX11'>Xlib — C Language X Interface</olink>. + + </para> + </listitem> + </varlistentry> +</variablelist> + +<para> +<xref linkend='XtGrabKey' xrefstyle='select: title'/> +calls +<function>XGrabKey</function> +specifying the widget's window as the grab +window if the widget is realized. The remaining arguments are exactly +as for +<function>XGrabKey</function>. +If the widget is not realized, or is later unrealized, the call to +<function>XGrabKey</function> +is performed (again) when +the widget is realized and its window becomes mapped. In the future, +if +<xref linkend='XtDispatchEvent' xrefstyle='select: title'/> +is called with a +<function>KeyPress</function> +event matching the specified keycode and modifiers (which may be +<function>AnyKey</function> +or +<function>AnyModifier</function>, +respectively) for the +widget's window, the Intrinsics will call +<xref linkend='XtUngrabKeyboard' xrefstyle='select: title'/> +with the timestamp from the +<function>KeyPress</function> +event if either of the following conditions is true: +</para> +<itemizedlist spacing='compact'> + <listitem> + <para> +There is a modal cascade and the widget is not in +the active subset of the cascade and the keyboard was not previously +grabbed, or + </para> + </listitem> + <listitem> + <para> +<function>XFilterEvent</function> +returns +<function>True</function>. + </para> + </listitem> +</itemizedlist> +<para> +To cancel a passive key grab, use +<xref linkend='XtUngrabKey' xrefstyle='select: title'/>. +</para> + +<funcsynopsis id='XtUngrabKey'> +<funcprototype> +<funcdef>void <function>XtUngrabKey</function></funcdef> + <paramdef>Widget <parameter>widget</parameter></paramdef> + <paramdef>KeyCode <parameter>keycode</parameter></paramdef> + <paramdef>Modifiers <parameter>modifiers</parameter></paramdef> +</funcprototype> +</funcsynopsis> + +<variablelist> + <varlistentry> + <term> + <emphasis remap='I'>widget</emphasis> + </term> + <listitem> + <para> +Specifies the widget in whose window the key was grabbed. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>keycode</emphasis> + </term> + <term> + <emphasis remap='I'>modifiers</emphasis> + </term> + <listitem> + <para> +Specify arguments to +<function>XUngrabKey</function>; +see <olink targetdoc='libX11' targetptr='Keyboard_Grabbing'>Section 12.2</olink> +in <olink targetdoc='libX11' targetptr='libX11'>Xlib — C Language X Interface</olink>. + </para> + </listitem> + </varlistentry> +</variablelist> + +<para> +The +<xref linkend='XtUngrabKey' xrefstyle='select: title'/> +procedure calls +<function>XUngrabKey</function> +specifying the widget's +window as the ungrab window if the widget is realized. The remaining +arguments are exactly as for +<function>XUngrabKey</function>. +If the widget is not realized, +<xref linkend='XtUngrabKey' xrefstyle='select: title'/> +removes a deferred +<xref linkend='XtGrabKey' xrefstyle='select: title'/> +request, if any, for the specified widget, keycode, and modifiers. +</para> + +<para> +To actively grab the keyboard, use +<xref linkend='XtGrabKeyboard' xrefstyle='select: title'/>. +</para> + +<funcsynopsis id='XtGrabKeyboard'> +<funcprototype> +<funcdef>int <function>XtGrabKeyboard</function></funcdef> + <paramdef>Widget <parameter>widget</parameter></paramdef> + <paramdef>Boolean <parameter>owner_events</parameter></paramdef> + <paramdef>int <parameter>pointer_mode</parameter></paramdef> + <paramdef>Time <parameter>time</parameter></paramdef> +</funcprototype> +</funcsynopsis> + +<variablelist> + <varlistentry> + <term> + <emphasis remap='I'>widget</emphasis> + </term> + <listitem> + <para> +Specifies the widget for whose window the keyboard is to be grabbed. +Must be of class Core or any subclass thereof. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>owner_events</emphasis> + </term> + <term> + <emphasis remap='I'>pointer_mode</emphasis> + </term> + <term> + <emphasis remap='I'>keyboard_mode</emphasis> + </term> + <term> + <emphasis remap='I'>time</emphasis> + </term> + <listitem> + <para> +Specify arguments to +<function>XGrabKeyboard</function>; +see <olink targetdoc='libX11' targetptr='Keyboard_Grabbing'>Section 12.2</olink> +in <olink targetdoc='libX11' targetptr='libX11'>Xlib — C Language X Interface</olink>. + </para> + </listitem> + </varlistentry> +</variablelist> + +<para> +If the specified widget is realized, +<xref linkend='XtGrabKeyboard' xrefstyle='select: title'/> +calls +<function>XGrabKeyboard</function> +specifying the widget's window as the grab window. The remaining +arguments and return value are exactly as for +<function>XGrabKeyboard</function>. +If the widget is not realized, +<xref linkend='XtGrabKeyboard' xrefstyle='select: title'/> +immediately returns +<function>GrabNotViewable</function>. +No future automatic ungrab is implied by +<xref linkend='XtGrabKeyboard' xrefstyle='select: title'/>. +</para> + +<para> +To cancel an active keyboard grab, use +<xref linkend='XtUngrabKeyboard' xrefstyle='select: title'/>. +</para> + +<funcsynopsis id='XtUngrabKeyboard'> +<funcprototype> +<funcdef>void <function>XtUngrabKeyboard</function></funcdef> + <paramdef>Widget <parameter>widget</parameter></paramdef> + <paramdef>Time <parameter>time</parameter></paramdef> +</funcprototype> +</funcsynopsis> + +<variablelist> + <varlistentry> + <term> + <emphasis remap='I'>widget</emphasis> + </term> + <listitem> + <para> +Specifies the widget that has the active keyboard grab. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>time</emphasis> + </term> + <listitem> + <para> +Specifies the additional argument to +<function>XUngrabKeyboard</function>; +see <olink targetdoc='libX11' targetptr='Keyboard_Grabbing'>Section 12.2</olink> +in <olink targetdoc='libX11' targetptr='libX11'>Xlib — C Language X Interface</olink>. + </para> + </listitem> + </varlistentry> +</variablelist> + +<para> +<xref linkend='XtUngrabKeyboard' xrefstyle='select: title'/> +calls +<function>XUngrabKeyboard</function> +with the specified time. +</para> + +<para> +To passively grab a single pointer button, use +<xref linkend='XtGrabButton' xrefstyle='select: title'/>. +</para> + +<funcsynopsis id='XtGrabButton'> +<funcprototype> +<funcdef>void <function>XtGrabButton</function></funcdef> + <paramdef>Widget <parameter>widget</parameter></paramdef> + <paramdef>int <parameter>button</parameter></paramdef> + <paramdef>Modifiers <parameter>modifiers</parameter></paramdef> + <paramdef>Boolean <parameter>owner_events</parameter></paramdef> + <paramdef>unsigned int <parameter>event_mask</parameter></paramdef> + <paramdef>int <parameter>pointer_mode</parameter></paramdef> + <paramdef>Window <parameter>confine_to</parameter></paramdef> + <paramdef>Cursor <parameter>cursor</parameter></paramdef> +</funcprototype> +</funcsynopsis> + +<variablelist> + <varlistentry> + <term> + <emphasis remap='I'>widget</emphasis> + </term> + <listitem> + <para> +Specifies the widget in whose window the button is to be grabbed. Must be of class Core or any subclass thereof. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>button</emphasis> + </term> + <term> + <emphasis remap='I'>modifiers</emphasis> + </term> + <term> + <emphasis remap='I'>owner_events</emphasis> + </term> + <term> + <emphasis remap='I'>event_mask</emphasis> + </term> + <term> + <emphasis remap='I'>pointer_mode</emphasis> + </term> + <term> + <emphasis remap='I'>keyboard_mode</emphasis> + </term> + <term> + <emphasis remap='I'>confine_to</emphasis> + </term> + <term> + <emphasis remap='I'>cursor</emphasis> + </term> + <listitem> + <para> +Specify arguments to +<function>XGrabButton</function>; +see <olink targetdoc='libX11' targetptr='Pointer_Grabbing'>Section 12.1</olink> +in <olink targetdoc='libX11' targetptr='libX11'>Xlib — C Language X Interface</olink>. + </para> + </listitem> + </varlistentry> +</variablelist> + +<para> +<xref linkend='XtGrabButton' xrefstyle='select: title'/> +calls +<function>XGrabButton</function> +specifying the widget's window as the +grab window if the widget is realized. The remaining arguments are +exactly as for +<function>XGrabButton</function>. +If the widget is not realized, or is later unrealized, the call to +<function>XGrabButton</function> +is performed (again) +when the widget is realized and its window becomes mapped. In the +future, if +<xref linkend='XtDispatchEvent' xrefstyle='select: title'/> +is called with a +<function>ButtonPress</function> +event matching the specified button and modifiers (which may be +<function>AnyButton</function> +or +<function>AnyModifier</function>, +respectively) +for the widget's window, the Intrinsics will call +<xref linkend='XtUngrabPointer' xrefstyle='select: title'/> +with the timestamp from the +<function>ButtonPress</function> +event if either of the following conditions is true: +</para> +<itemizedlist spacing='compact'> + <listitem> + <para> +There is a modal cascade and the +widget is not in the active subset of the cascade and the pointer was +not previously grabbed, or + </para> + </listitem> + <listitem> + <para> +<function>XFilterEvent</function> +returns +<function>True</function>. + </para> + </listitem> +</itemizedlist> +<para> +To cancel a passive button grab, use +<xref linkend='XtUngrabButton' xrefstyle='select: title'/>. +</para> + +<funcsynopsis id='XtUngrabButton'> +<funcprototype> +<funcdef>void <function>XtUngrabButton</function></funcdef> + <paramdef>Widget <parameter>widget</parameter></paramdef> + <paramdef>unsigned int <parameter>button</parameter></paramdef> + <paramdef>Modifiers <parameter>modifiers</parameter></paramdef> +</funcprototype> +</funcsynopsis> + +<variablelist> + <varlistentry> + <term> + <emphasis remap='I'>widget</emphasis> + </term> + <listitem> + <para> +Specifies the widget in whose window the button was grabbed. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>button</emphasis> + </term> + <term> + <emphasis remap='I'>modifiers</emphasis> + </term> + <listitem> + <para> +Specify arguments to +<function>XUngrabButton</function>; +see <olink targetdoc='libX11' targetptr='Pointer_Grabbing'>Section 12.1</olink> +in <olink targetdoc='libX11' targetptr='libX11'>Xlib — C Language X Interface</olink>. + </para> + </listitem> + </varlistentry> +</variablelist> + +<para> +The +<xref linkend='XtUngrabButton' xrefstyle='select: title'/> +procedure calls +<function>XUngrabButton</function> +specifying the +widget's window as the ungrab window if the widget is realized. The +remaining arguments are exactly as for +<function>XUngrabButton</function>. +If the widget is not realized, +<xref linkend='XtUngrabButton' xrefstyle='select: title'/> +removes a deferred +<xref linkend='XtGrabButton' xrefstyle='select: title'/> +request, if any, for the specified widget, button, and modifiers. +</para> + +<para> +To actively grab the pointer, use +<xref linkend='XtGrabPointer' xrefstyle='select: title'/>. +</para> + +<funcsynopsis id='XtGrabPointer'> +<funcprototype> +<funcdef>int <function>XtGrabPointer</function></funcdef> + <paramdef>Widget <parameter>widget</parameter></paramdef> + <paramdef>Boolean <parameter>owner_events</parameter></paramdef> + <paramdef>unsigned int <parameter>event_mask</parameter></paramdef> + <paramdef>int <parameter>pointer_mode</parameter></paramdef> + <paramdef>Window <parameter>confine_to</parameter></paramdef> + <paramdef>Cursor <parameter>cursor</parameter></paramdef> + <paramdef>Time <parameter>time</parameter></paramdef> +</funcprototype> +</funcsynopsis> + +<variablelist> + <varlistentry> + <term> + <emphasis remap='I'>widget</emphasis> + </term> + <listitem> + <para> +Specifies the widget for whose window the pointer is to be grabbed. Must be of class Core or any subclass thereof. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>owner_events</emphasis> + </term> + <term> + <emphasis remap='I'>event_mask</emphasis> + </term> + <term> + <emphasis remap='I'>pointer_mode</emphasis> + </term> + <term> + <emphasis remap='I'>keyboard_mode</emphasis> + </term> + <term> + <emphasis remap='I'>confine_to</emphasis> + </term> + <term> + <emphasis remap='I'>cursor</emphasis> + </term> + <term> + <emphasis remap='I'>time</emphasis> + </term> + <listitem> + <para> +Specify arguments to +<function>XGrabPointer</function>; +see <olink targetdoc='libX11' targetptr='Pointer_Grabbing'>Section 12.1</olink> +in <olink targetdoc='libX11' targetptr='libX11'>Xlib — C Language X Interface</olink>. + </para> + </listitem> + </varlistentry> +</variablelist> + +<para> +If the specified widget is realized, +<xref linkend='XtGrabPointer' xrefstyle='select: title'/> +calls +<function>XGrabPointer</function>, +specifying the widget's window as the grab window. The remaining +arguments and return value are exactly as for +<function>XGrabPointer</function>. +If the widget is not realized, +<xref linkend='XtGrabPointer' xrefstyle='select: title'/> +immediately returns +<function>GrabNotViewable</function>. +No future automatic ungrab is implied by +<xref linkend='XtGrabPointer' xrefstyle='select: title'/>. +</para> + +<para> +To cancel an active pointer grab, use +<xref linkend='XtUngrabPointer' xrefstyle='select: title'/>. +</para> + +<funcsynopsis id='XtUngrabPointer'> +<funcprototype> +<funcdef>void <function>XtUngrabPointer</function></funcdef> + <paramdef>Widget <parameter>widget</parameter></paramdef> + <paramdef>Time <parameter>time</parameter></paramdef> +</funcprototype> +</funcsynopsis> + +<variablelist> + <varlistentry> + <term> + <emphasis remap='I'>widget</emphasis> + </term> + <listitem> + <para> +Specifies the widget that has the active pointer grab. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>time</emphasis> + </term> + <listitem> + <para> +Specifies the time argument to +<function>XUngrabPointer</function>; +see <olink targetdoc='libX11' targetptr='Pointer_Grabbing'>Section 12.1</olink> +in <olink targetdoc='libX11' targetptr='libX11'>Xlib — C Language X Interface</olink>. + </para> + </listitem> + </varlistentry> +</variablelist> + +<para> +<xref linkend='XtUngrabPointer' xrefstyle='select: title'/> +calls +<function>XUngrabPointer</function> +with the specified time. +</para> +</sect2> +</sect1> + +<sect1 id="Focusing_Events_on_a_Child"> +<title>Focusing Events on a Child</title> +<para> +To redirect keyboard input to a normal descendant of a +widget without calling +<function>XSetInputFocus</function>, +use +<xref linkend='XtSetKeyboardFocus' xrefstyle='select: title'/>. +</para> + +<funcsynopsis id='XtSetKeyboardFocus'> +<funcprototype> +<funcdef>void <function>XtSetKeyboardFocus</function></funcdef> + <paramdef>Widget <parameter>subtree</parameter></paramdef> +</funcprototype> +</funcsynopsis> + +<variablelist> + <varlistentry> + <term> + <emphasis remap='I'>subtree</emphasis> + </term> + <listitem> + <para> +Specifies the subtree of the hierarchy for which the keyboard focus is +to be set. Must be of class Core or any subclass thereof. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>descendant</emphasis> + </term> + <listitem> + <para> +Specifies either the normal (non-pop-up) descendant of <emphasis remap='I'>subtree</emphasis> to which +keyboard events are logically directed, or +<function>None</function>. +It is not an error to specify +<function>None</function> +when no input focus was previously set. Must be of class Object or any subclass thereof. + </para> + </listitem> + </varlistentry> +</variablelist> + +<para> +<xref linkend='XtSetKeyboardFocus' xrefstyle='select: title'/> +causes +<xref linkend='XtDispatchEvent' xrefstyle='select: title'/> +to remap keyboard events occurring within the specified subtree +and dispatch them to the specified descendant widget or to an ancestor. +If the descendant's class is not a subclass of Core, the descendant is +replaced by its closest windowed ancestor. +</para> + +<para> +When there is no modal cascade, keyboard events can be dispatched +to a widget in one of five ways. Assume the server delivered the +event to the window for widget E (because of X input focus, key or +keyboard grabs, or pointer position). +</para> +<itemizedlist spacing='compact'> + <listitem> + <para> +If neither E nor any of E's ancestors have redirected the keyboard +focus, or if the event activated a grab for E as specified by a call +to +<xref linkend='XtGrabKey' xrefstyle='select: title'/> +with any value of <emphasis remap='I'>owner_events</emphasis>, or +if the keyboard is actively grabbed by E with <emphasis remap='I'>owner_events</emphasis> +<function>False</function> +via +<xref linkend='XtGrabKeyboard' xrefstyle='select: title'/> +or +<xref linkend='XtGrabKey' xrefstyle='select: title'/> +on a previous key press, the event is dispatched to E. + </para> + </listitem> + <listitem> + <para> +Beginning with the ancestor of E closest to the root that has +redirected the keyboard focus or E if no such ancestor exists, if +the target of that focus redirection has in turn redirected the +keyboard focus, recursively follow this focus chain to find a widget +F that has not redirected focus. + </para> + </listitem> + <listitem> + <itemizedlist spacing='compact'> + <listitem> + <para> +If E is the final focus target widget F or a descendant of F, the +event is dispatched to E. + </para> + </listitem> + <listitem> + <para> +If E is not F, an ancestor of F, or a descendant of F, and the event +activated a grab for E as specified by a call to +<xref linkend='XtGrabKey' xrefstyle='select: title'/> +for E, +<xref linkend='XtUngrabKeyboard' xrefstyle='select: title'/> +is called. + </para> + </listitem> + <listitem> + <para> +If E is an ancestor of F, and the event is a key press, and either + </para> + </listitem> + <listitem> + <itemizedlist spacing='compact'> + <listitem> + <para> +E has grabbed the key with +<xref linkend='XtGrabKey' xrefstyle='select: title'/> +and <emphasis remap='I'>owner_events</emphasis> +<function>False</function>, +or + </para> + </listitem> + <listitem> + <para> +E has grabbed the key with +<xref linkend='XtGrabKey' xrefstyle='select: title'/> +and <emphasis remap='I'>owner_events</emphasis> +<function>True</function>, +and the coordinates of the event are outside the rectangle specified +by E's geometry, +then the event is dispatched to E. + </para> + </listitem> + </itemizedlist> + </listitem> + <listitem> + <para> +Otherwise, define A as the closest common ancestor of E and F: + </para> + </listitem> + <listitem> + <itemizedlist spacing='compact'> + <listitem> + <para> +If there is an active keyboard grab for any widget via either +<xref linkend='XtGrabKeyboard' xrefstyle='select: title'/> +or +<xref linkend='XtGrabKey' xrefstyle='select: title'/> +on a previous key press, or +if no widget between F and A (noninclusive) has grabbed +the key and modifier combination with +<xref linkend='XtGrabKey' xrefstyle='select: title'/> +and any value of <emphasis remap='I'>owner_events</emphasis>, the event is dispatched to F. + </para> + </listitem> + <listitem> + <para> +Else, the event is dispatched to the ancestor of F closest to A +that has grabbed the key and modifier combination with +<xref linkend='XtGrabKey' xrefstyle='select: title'/>. + </para> + </listitem> + </itemizedlist> + </listitem> + </itemizedlist> + </listitem> +</itemizedlist> +<para> +When there is a modal cascade, if the final destination widget as +identified above is in the active subset of the cascade, the event is +dispatched; otherwise the event is remapped to a spring-loaded shell +or discarded. +Regardless of where it is dispatched, the Intrinsics do not modify +the contents of the event. +</para> + +<para> +When <emphasis remap='I'>subtree</emphasis> or one of its descendants acquires the X input focus +or the pointer moves into the subtree such that keyboard events would +now be delivered to the subtree, a +<function>FocusIn</function> +event is generated for the descendant if +<function>FocusChange</function> +events have been selected by the descendant. +Similarly, when <emphasis remap='I'>subtree</emphasis> loses the X input focus +or the keyboard focus for one of its ancestors, a +<function>FocusOut</function> +event is generated for descendant if +<function>FocusChange</function> +events have been selected by the descendant. +</para> + +<para> +A widget tree may also actively manage the X server input focus. To +do so, a widget class specifies an accept_focus procedure. +</para> + +<para> +The accept_focus procedure pointer is of type +<xref linkend='XtAcceptFocusProc' xrefstyle='select: title'/>. +</para> + +<funcsynopsis id='XtAcceptFocusProc'> +<funcprototype> +<funcdef>Boolean <function>*XtAcceptFocusProc</function></funcdef> + + <paramdef>Widget <parameter>w</parameter></paramdef> + <paramdef>Time *<parameter>time</parameter></paramdef> +</funcprototype> +</funcsynopsis> + +<variablelist> + <varlistentry> + <term> + <emphasis remap='I'>w</emphasis> + </term> + <listitem> + <para> +Specifies the widget. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>time</emphasis> + </term> + <listitem> + <para> +Specifies the X time of the event causing the accept focus. + </para> + </listitem> + </varlistentry> +</variablelist> + +<para> +Widgets that need the input focus can call +<function>XSetInputFocus</function> +explicitly, pursuant to the restrictions of the <emphasis remap='I'>Inter-Client Communication Conventions Manual.</emphasis>. +To allow outside agents, such as the parent, +to cause a widget to take the input focus, +every widget exports an accept_focus procedure. +The widget returns a value indicating +whether it actually took the focus or not, +so that the parent can give the focus to another widget. +Widgets that need to know when they lose the input focus must use +the Xlib focus notification mechanism explicitly +(typically by specifying translations for +<function>FocusIn</function> +and +<function>FocusOut</function> +events). +Widgets classes that never want the input focus should set the +<emphasis remap='I'>accept_focus</emphasis> field to NULL. +</para> + +<para> +To call a widget's accept_focus procedure, use +<xref linkend='XtCallAcceptFocus' xrefstyle='select: title'/>. +</para> + +<funcsynopsis id='XtCallAcceptFocus'> +<funcprototype> +<funcdef>Boolean <function>XtCallAcceptFocus</function></funcdef> + <paramdef>Widget <parameter>w</parameter></paramdef> + <paramdef>Time *<parameter>time</parameter></paramdef> +</funcprototype> +</funcsynopsis> + +<variablelist> + <varlistentry> + <term> + <emphasis remap='I'>w</emphasis> + </term> + <listitem> + <para> +Specifies the widget. Must be of class Core or any subclass thereof. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>time</emphasis> + </term> + <listitem> + <para> +Specifies the X time of the event that is causing the focus change. + </para> + </listitem> + </varlistentry> +</variablelist> + +<para> +The +<xref linkend='XtCallAcceptFocus' xrefstyle='select: title'/> +function calls the specified widget's accept_focus procedure, +passing it the specified widget and time, and returns what the accept_focus +procedure returns. +If <emphasis remap='I'>accept_focus</emphasis> is NULL, +<xref linkend='XtCallAcceptFocus' xrefstyle='select: title'/> +returns +<function>False</function>. +</para> +<sect2 id="Events_for_Drawables_That_Are_Not_a_Widget_s_Window"> +<title>Events for Drawables That Are Not a Widget's Window</title> +<para> +Sometimes an application must handle events for drawables that are not +associated with widgets in its widget tree. Examples include handling +<function>GraphicsExpose</function> +and +<function>NoExpose</function> +events on Pixmaps, and handling +<function>PropertyNotify</function> +events on the root window. +</para> + +<para> +To register a drawable with the Intrinsics event dispatching, use +<xref linkend='XtRegisterDrawable' xrefstyle='select: title'/>. +</para> + +<funcsynopsis id='XtRegisterDrawable'> +<funcprototype> +<funcdef>void <function>XtRegisterDrawable</function></funcdef> + <paramdef>Display *<parameter>display</parameter></paramdef> + <paramdef>Drawable <parameter>drawable</parameter></paramdef> + <paramdef>Widget <parameter>widget</parameter></paramdef> +</funcprototype> +</funcsynopsis> + +<variablelist> + <varlistentry> + <term> + <emphasis remap='I'>display</emphasis> + </term> + <listitem> + <para> +Specifies the drawable's display. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>drawable</emphasis> + </term> + <listitem> + <para> +Specifies the drawable to register. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>widget</emphasis> + </term> + <listitem> + <para> +Specifies the widget to register the drawable for. + </para> + </listitem> + </varlistentry> +</variablelist> + +<para> +<xref linkend='XtRegisterDrawable' xrefstyle='select: title'/> +associates the specified drawable with the specified widget +so that future calls to +<xref linkend='XtWindowToWidget' xrefstyle='select: title'/> +with the drawable will return the widget. +The default event dispatcher will dispatch future events that +arrive for the drawable to the widget in the same manner as +events that contain the widget's window. +</para> + +<para> +If the drawable is already registered with another widget, or if the +drawable is the window of a widget in the client's widget tree, the +results of calling +<xref linkend='XtRegisterDrawable' xrefstyle='select: title'/> +are undefined. +</para> + +<para> +To unregister a drawable with the Intrinsics event dispatching, use +<xref linkend='XtUnregisterDrawable' xrefstyle='select: title'/>. +</para> + +<funcsynopsis id='XtUnregisterDrawable'> +<funcprototype> +<funcdef>void <function>XtUnregisterDrawable</function></funcdef> + <paramdef>Display *<parameter>display</parameter></paramdef> + <paramdef>Drawable <parameter>drawable</parameter></paramdef> +</funcprototype> +</funcsynopsis> + +<variablelist> + <varlistentry> + <term> + <emphasis remap='I'>display</emphasis> + </term> + <listitem> + <para> +Specifies the drawable's display. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>drawable</emphasis> + </term> + <listitem> + <para> +Specifies the drawable to unregister. + </para> + </listitem> + </varlistentry> +</variablelist> + +<para> +<xref linkend='XtUnregisterDrawable' xrefstyle='select: title'/> +removes an association created with +<xref linkend='XtRegisterDrawable' xrefstyle='select: title'/>. +If the drawable is the window of a widget in the client's widget tree +the results of calling +<xref linkend='XtUnregisterDrawable' xrefstyle='select: title'/> +are undefined. +</para> +</sect2> +</sect1> + +<sect1 id="Querying_Event_Sources"> +<title>Querying Event Sources</title> +<para> +The event manager provides several functions to examine and read events +(including file and timer events) that are in the queue. +The next three functions are Intrinsics equivalents of the +<function>XPending</function>, +<function>XPeekEvent</function>, +and +<function>XNextEvent</function> +Xlib calls. +</para> + +<para> +To determine if there are any events on the input queue for a given application, +use +<xref linkend='XtAppPending' xrefstyle='select: title'/>. +</para> + +<funcsynopsis id='XtAppPending'> +<funcprototype> +<funcdef>XtInputMask <function>XtAppPending</function></funcdef> + <paramdef>XtAppContext <parameter>app_context</parameter></paramdef> +</funcprototype> +</funcsynopsis> + +<variablelist> + <varlistentry> + <term> + <emphasis remap='I'>app_context</emphasis> + </term> + <listitem> + <para> +Specifies the application context that identifies the application to check. + </para> + </listitem> + </varlistentry> +</variablelist> + +<para> +The +<xref linkend='XtAppPending' xrefstyle='select: title'/> +function returns a nonzero value if there are +events pending from the X server, timer pending, other input sources +pending, or signal sources pending. The +value returned is a bit mask that is the OR of +<function>XtIMXEvent</function>, +<function>XtIMTimer</function>, +<function>XtIMAlternateInput</function>, +and +<function>XtIMSignal</function> +(see +<function>XtAppProcessEvent ).</function> +If there are no events pending, +<xref linkend='XtAppPending' xrefstyle='select: title'/> +flushes the output buffers of each Display in the application context +and returns zero. +</para> + +<para> +To return the event from the head of a given application's input queue +without removing input from the queue, use +<xref linkend='XtAppPeekEvent' xrefstyle='select: title'/>. +</para> + +<funcsynopsis id='XtAppPeekEvent'> +<funcprototype> +<funcdef>Boolean <function>XtAppPeekEvent</function></funcdef> + <paramdef>XtAppContext <parameter>app_context</parameter></paramdef> + <paramdef>XEvent *<parameter>event_return</parameter></paramdef> +</funcprototype> +</funcsynopsis> + +<variablelist> + <varlistentry> + <term> + <emphasis remap='I'>app_context</emphasis> + </term> + <listitem> + <para> +Specifies the application context that identifies the application. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>event_return</emphasis> + </term> + <listitem> + <para> +Returns the event information to the specified event structure. + </para> + </listitem> + </varlistentry> +</variablelist> + +<para> +If there is an X event in the queue, +<xref linkend='XtAppPeekEvent' xrefstyle='select: title'/> +copies it into <emphasis remap='I'>event_return</emphasis> and returns +<function>True</function>. +If no X input is on the queue, +<xref linkend='XtAppPeekEvent' xrefstyle='select: title'/> +flushes the output buffers of each Display in the application context +and blocks until some input is available +(possibly calling some timeout callbacks in the interim). +If the next available input is an X event, +<xref linkend='XtAppPeekEvent' xrefstyle='select: title'/> +fills in <emphasis remap='I'>event_return</emphasis> and returns +<function>True</function>. +Otherwise, the input is for an input source +registered with +<xref linkend='XtAppAddInput' xrefstyle='select: title'/>, +and +<xref linkend='XtAppPeekEvent' xrefstyle='select: title'/> +returns +<function>False</function>. +The sample implementations provides XtAppPeekEvent as described. Timeout callbacks +are called while blocking for input. If some input for an input source is +available, +<xref linkend='XtAppPeekEvent' xrefstyle='select: title'/> +will return +<function>True</function> +without returning an event. +</para> + +<para> +To remove and return the event +from the head of a given application's X event queue, +use +<xref linkend='XtAppNextEvent' xrefstyle='select: title'/>. +</para> + +<funcsynopsis id='XtAppNextEvent'> +<funcprototype> +<funcdef>void <function>XtAppNextEvent</function></funcdef> + <paramdef>XtAppContext <parameter>app_context</parameter></paramdef> + <paramdef>XEvent *<parameter>event_return</parameter></paramdef> +</funcprototype> +</funcsynopsis> + +<variablelist> + <varlistentry> + <term> + <emphasis remap='I'>app_context</emphasis> + </term> + <listitem> + <para> +Specifies the application context that identifies the application. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>event_return</emphasis> + </term> + <listitem> + <para> +Returns the event information to the specified event structure. + </para> + </listitem> + </varlistentry> +</variablelist> + +<para> +If the X event queue is empty, +<xref linkend='XtAppNextEvent' xrefstyle='select: title'/> +flushes the X output buffers of each Display in the application context +and waits for an X event while looking at the other input sources +and timeout values and calling any callback procedures triggered by them. +This wait time can be used for background processing; +see <xref linkend='Adding_Background_Work_Procedures' />. +</para> +</sect1> + +<sect1 id="Dispatching_Events"> +<title>Dispatching Events</title> +<para> +The Intrinsics provide functions that dispatch events +to widgets or other application code. +Every client interested in X events on a widget uses +<xref linkend='XtAddEventHandler' xrefstyle='select: title'/> +to register which events it is +interested in and a procedure (event handler) to be called +when the event happens in that window. +The translation manager automatically registers event handlers for widgets +that use translation tables; see <xref linkend='Translation_Management' />. +</para> + +<para> +Applications that need direct control of the processing of different types +of input should use +<xref linkend='XtAppProcessEvent' xrefstyle='select: title'/>. +</para> + +<funcsynopsis id='XtAppProcessEvent'> +<funcprototype> +<funcdef>void <function>XtAppProcessEvent</function></funcdef> + <paramdef>XtAppContext <parameter>app_context</parameter></paramdef> + <paramdef>XtInputMask <parameter>mask</parameter></paramdef> +</funcprototype> +</funcsynopsis> + +<variablelist> + <varlistentry> + <term> + <emphasis remap='I'>app_context</emphasis> + </term> + <listitem> + <para> +Specifies the application context that identifies the +application for which to process input. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>mask</emphasis> + </term> + <listitem> + <para> +Specifies what types of events to process. +The mask is the bitwise inclusive OR of any combination of +<function>XtIMXEvent</function>, +<function>XtIMTimer</function>, +<function>XtIMAlternateInput</function>, +and +<function>XtIMSignal</function>. +As a convenience, +<function>Intrinsic.h</function> +defines the symbolic name +<function>XtIMAll</function> +to be the bitwise inclusive OR of these four event types. + </para> + </listitem> + </varlistentry> +</variablelist> + +<para> +The +<xref linkend='XtAppProcessEvent' xrefstyle='select: title'/> +function processes one timer, input source, signal source, or X event. +If there is no event or input of the appropriate type to process, then +<xref linkend='XtAppProcessEvent' xrefstyle='select: title'/> +blocks until there is. +If there is more than one type of input available to process, +it is undefined which will get processed. +Usually, this procedure is not called by client applications; see +<xref linkend='XtAppMainLoop' xrefstyle='select: title'/>. +<xref linkend='XtAppProcessEvent' xrefstyle='select: title'/> +processes timer events by calling any appropriate timer callbacks, +input sources by calling any appropriate input callbacks, +signal source by calling any appropriate signal callbacks, +and X events by +calling +<xref linkend='XtDispatchEvent' xrefstyle='select: title'/>. +</para> + +<para> +When an X event is received, +it is passed to +<xref linkend='XtDispatchEvent' xrefstyle='select: title'/>, +which calls the appropriate event handlers +and passes them the widget, the event, and client-specific data +registered with each procedure. +If no handlers for that event are registered, +the event is ignored and the dispatcher simply returns. +</para> + +<para> +To dispatch an event returned by +<xref linkend='XtAppNextEvent' xrefstyle='select: title'/>, +retrieved directly from the Xlib queue, or synthetically constructed, +to any registered event filters or event handlers, call +<xref linkend='XtDispatchEvent' xrefstyle='select: title'/>. +</para> + +<funcsynopsis id='XtDispatchEvent'> +<funcprototype> +<funcdef>Boolean <function>XtDispatchEvent</function></funcdef> + <paramdef>XEvent *<parameter>event</parameter></paramdef> +</funcprototype> +</funcsynopsis> + +<variablelist> + <varlistentry> + <term> + <emphasis remap='I'>event</emphasis> + </term> + <listitem> + <para> +Specifies a pointer to the event structure to be dispatched +to the appropriate event handlers. + </para> + </listitem> + </varlistentry> +</variablelist> + +<para> +The +<xref linkend='XtDispatchEvent' xrefstyle='select: title'/> +function first calls +<function>XFilterEvent</function> +with the <emphasis remap='I'>event</emphasis> and the window of the widget to which the +Intrinsics intend to dispatch the event, or the event window if +the Intrinsics would not dispatch the event to any handlers. +If +<function>XFilterEvent</function> +returns +<function>True</function> +and the event activated a server grab as identified +by a previous call to +<xref linkend='XtGrabKey' xrefstyle='select: title'/> +or +<xref linkend='XtGrabButton' xrefstyle='select: title'/>, +<xref linkend='XtDispatchEvent' xrefstyle='select: title'/> +calls +<xref linkend='XtUngrabKeyboard' xrefstyle='select: title'/> +or +<xref linkend='XtUngrabPointer' xrefstyle='select: title'/> +with the timestamp from the event and immediately returns +<function>True</function>. +If +<function>XFilterEvent</function> +returns +<function>True</function> +and a grab was not activated, +<xref linkend='XtDispatchEvent' xrefstyle='select: title'/> +just immediately returns +<function>True</function>. +Otherwise, +<xref linkend='XtDispatchEvent' xrefstyle='select: title'/> +sends the event to the event handler functions that +have been previously registered with the dispatch routine. +<xref linkend='XtDispatchEvent' xrefstyle='select: title'/> +returns +<function>True</function> +if +<function>XFilterEvent</function> +returned +<function>True</function>, +or if the event was dispatched to some handler, and +<function>False</function> +if it found no handler to which to dispatch the event. +<xref linkend='XtDispatchEvent' xrefstyle='select: title'/> +records the last timestamp in any event that +contains a timestamp (see +<function>XtLastTimestampProcessed ),</function> +regardless of whether it was filtered or dispatched. +If a modal cascade is active with <emphasis remap='I'>spring_loaded</emphasis> +<function>True</function>, +and if the event is a remap event as defined by +<xref linkend='XtAddGrab' xrefstyle='select: title'/>, +<xref linkend='XtDispatchEvent' xrefstyle='select: title'/> +may dispatch the event a second time. If it does so, +<xref linkend='XtDispatchEvent' xrefstyle='select: title'/> +will call +<function>XFilterEvent</function> +again with the window of the spring-loaded widget prior to the second +dispatch, and if +<function>XFilterEvent</function> +returns +<function>True</function>, +the second dispatch will not be performed. +</para> +</sect1> + +<sect1 id="The_Application_Input_Loop"> +<title>The Application Input Loop</title> +<para> +To process all input from a given application in a continuous loop, +use the convenience procedure +<xref linkend='XtAppMainLoop' xrefstyle='select: title'/>. +</para> + +<funcsynopsis id='XtAppMainLoop'> +<funcprototype> +<funcdef>void <function>XtAppMainLoop</function></funcdef> + <paramdef>XtAppContext <parameter>app_context</parameter></paramdef> +</funcprototype> +</funcsynopsis> + +<variablelist> + <varlistentry> + <term> + <emphasis remap='I'>app_context</emphasis> + </term> + <listitem> + <para> +Specifies the application context that identifies the application. + </para> + </listitem> + </varlistentry> +</variablelist> + +<para> +The +<xref linkend='XtAppMainLoop' xrefstyle='select: title'/> +function first reads the next incoming X event by calling +<xref linkend='XtAppNextEvent' xrefstyle='select: title'/> +and then dispatches the event to the appropriate registered procedure +by calling +<xref linkend='XtDispatchEvent' xrefstyle='select: title'/>. +This constitutes the main loop of X Toolkit applications. +There is nothing special about +<xref linkend='XtAppMainLoop' xrefstyle='select: title'/>; +it simply calls +<xref linkend='XtAppNextEvent' xrefstyle='select: title'/> +and then +<xref linkend='XtDispatchEvent' xrefstyle='select: title'/> +in a conditional loop. +At the bottom of the loop, it checks to see if the specified +application context's destroy flag is set. +If the flag is set, the loop breaks. +The whole loop is enclosed between a matching +<xref linkend='XtAppLock' xrefstyle='select: title'/> +and +<xref linkend='XtAppUnlock' xrefstyle='select: title'/>. +</para> + +<para> +Applications can provide their own version of this loop, +which tests some global termination flag or tests that the number +of top-level widgets is larger than zero before circling back to the call to +<xref linkend='XtAppNextEvent' xrefstyle='select: title'/>. +</para> +</sect1> + +<sect1 id="Setting_and_Checking_the_Sensitivity_State_of_a_Widget"> +<title>Setting and Checking the Sensitivity State of a Widget</title> +<para> +Many widgets have a mode in which they assume a different appearance +(for example, are grayed out or stippled), do not respond to user events, +and become dormant. +</para> + +<para> +When dormant, +a widget is considered to be insensitive. +If a widget is insensitive, +the event manager does not dispatch any events to the widget +with an event type of +<function>KeyPress</function>, +<function>KeyRelease</function>, +<function>ButtonPress</function>, +<function>ButtonRelease</function>, +<function>MotionNotify</function>, +<function>EnterNotify</function>, +<function>LeaveNotify</function>, +<function>FocusIn</function>, +or +<function>FocusOut</function>. +</para> + +<para> +A widget can be insensitive because its <emphasis remap='I'>sensitive</emphasis> field is +<function>False</function> +or because one of its ancestors is insensitive and thus the widget's +<emphasis remap='I'>ancestor_sensitive</emphasis> field also is +<function>False</function>. +A widget can but does not need to distinguish these two cases visually. +</para> + +<note> +<para> +Pop-up shells will have +<emphasis remap='I'>ancestor_sensitive</emphasis> +<function>False</function> +if the parent was insensitive when the shell +was created. Since +<xref linkend='XtSetSensitive' xrefstyle='select: title'/> +on the parent will not +modify the resource of the pop-up child, clients are advised to include +a resource specification of the form +``*TransientShell.ancestorSensitive: True'' +in the application defaults resource file or to +otherwise ensure that the parent is +sensitive when creating pop-up shells. +</para> +</note> + +<para> +To set the sensitivity state of a widget, use +<xref linkend='XtSetSensitive' xrefstyle='select: title'/>. +</para> + +<funcsynopsis id='XtSetSensitive'> +<funcprototype> +<funcdef>void <function>XtSetSensitive</function></funcdef> + <paramdef>Widget <parameter>w</parameter></paramdef> + <paramdef>Boolean <parameter>sensitive</parameter></paramdef> +</funcprototype> +</funcsynopsis> + +<variablelist> + <varlistentry> + <term> + <emphasis remap='I'>w</emphasis> + </term> + <listitem> + <para> +Specifies the widget. Must be of class RectObj or any subclass thereof. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>sensitive</emphasis> + </term> + <listitem> + <para> +Specifies whether the widget should receive +keyboard, pointer, and focus events. + </para> + </listitem> + </varlistentry> +</variablelist> + +<para> +The +<xref linkend='XtSetSensitive' xrefstyle='select: title'/> +function first calls +<xref linkend='XtSetValues' xrefstyle='select: title'/> +on the current widget with an argument list specifying the +XtNsensitive resource and the new value. +If <emphasis remap='I'>sensitive</emphasis> is +<function>False</function> +and the widget's class is a subclass of +Composite, +<xref linkend='XtSetSensitive' xrefstyle='select: title'/> +recursively propagates the new value +down the child tree by calling +<xref linkend='XtSetValues' xrefstyle='select: title'/> +on each child to set <emphasis remap='I'>ancestor_sensitive</emphasis> to +<function>False</function>. +If <emphasis remap='I'>sensitive</emphasis> is +<function>True</function> +and the widget's class is a subclass of +Composite +and the widget's <emphasis remap='I'>ancestor_sensitive</emphasis> field is +<function>True</function>, +<xref linkend='XtSetSensitive' xrefstyle='select: title'/> +sets the <emphasis remap='I'>ancestor_sensitive</emphasis> of each child to +<function>True</function> +and then recursively calls +<xref linkend='XtSetValues' xrefstyle='select: title'/> +on each normal descendant that is now sensitive to set +<emphasis remap='I'>ancestor_sensitive</emphasis> to +<function>True</function>. +</para> + +<para> +<xref linkend='XtSetSensitive' xrefstyle='select: title'/> +calls +<xref linkend='XtSetValues' xrefstyle='select: title'/> +to change the <emphasis remap='I'>sensitive</emphasis> and <emphasis remap='I'>ancestor_sensitive</emphasis> fields +of each affected widget. +Therefore, when one of these changes, +the widget's set_values procedure should +take whatever display actions are needed +(for example, graying out or stippling the widget). +</para> + +<para> +<xref linkend='XtSetSensitive' xrefstyle='select: title'/> +maintains the invariant that, if the parent has either <emphasis remap='I'>sensitive</emphasis> +or <emphasis remap='I'>ancestor_sensitive</emphasis> +<function>False</function>, +then all children have <emphasis remap='I'>ancestor_sensitive</emphasis> +<function>False</function>. +</para> + +<para> +To check the current sensitivity state of a widget, +use +<xref linkend='XtIsSensitive' xrefstyle='select: title'/>. +</para> + +<funcsynopsis id='XtIsSensitive'> +<funcprototype> +<funcdef>Boolean <function>XtIsSensitive</function></funcdef> + <paramdef>Widget <parameter>w</parameter></paramdef> +</funcprototype> +</funcsynopsis> + +<variablelist> + <varlistentry> + <term> + <emphasis remap='I'>w</emphasis> + </term> + <listitem> + <para> +Specifies the object. Must be of class Object or any subclass thereof. + </para> + </listitem> + </varlistentry> +</variablelist> + +<para> +The +<xref linkend='XtIsSensitive' xrefstyle='select: title'/> +function returns +<function>True</function> +or +<function>False</function> +to indicate whether user input events are being dispatched. +If object's class is a subclass of RectObj and +both <emphasis remap='I'>sensitive</emphasis> and <emphasis remap='I'>ancestor_sensitive</emphasis> are +<function>True</function>, +<xref linkend='XtIsSensitive' xrefstyle='select: title'/> +returns +<function>True</function>; +otherwise, it returns +<function>False</function>. +</para> +</sect1> + +<sect1 id="Adding_Background_Work_Procedures"> +<title>Adding Background Work Procedures</title> +<para> +The Intrinsics have some limited support for background processing. +Because most applications spend most of their time waiting for input, +you can register an idle-time work procedure +that is called when the toolkit would otherwise block in +<xref linkend='XtAppNextEvent' xrefstyle='select: title'/> +or +<xref linkend='XtAppProcessEvent' xrefstyle='select: title'/>. +Work procedure pointers are of type +<xref linkend='XtWorkProc' xrefstyle='select: title'/>. +</para> + +<funcsynopsis id='XtWorkProc'> +<funcprototype> +<funcdef>typedef Boolean <function>(*XtWorkProc)</function></funcdef> + + <paramdef>XtPointer <parameter>client_data</parameter></paramdef> +</funcprototype> +</funcsynopsis> + +<variablelist> + <varlistentry> + <term> + <emphasis remap='I'>client_data</emphasis> + </term> + <listitem> + <para> +Passes the client data specified when the work procedure was registered. + </para> + </listitem> + </varlistentry> +</variablelist> + +<para> +This procedure should return +<function>True</function> +when it is done to indicate that it +should be removed. +If the procedure returns +<function>False</function>, +it will remain registered and called again when the +application is next idle. +Work procedures should be very judicious about how much they do. +If they run for more than a small part of a second, +interactive feel is likely to suffer. +</para> + +<para> +To register a work procedure for a given application, use +<xref linkend='XtAppAddWorkProc' xrefstyle='select: title'/>. +</para> + +<funcsynopsis id='XtAppAddWorkProc'> +<funcprototype> +<funcdef>XtWorkProcId <function>XtAppAddWorkProc</function></funcdef> + <paramdef>XtAppContext <parameter>app_context</parameter></paramdef> + <paramdef>XtWorkProc <parameter>proc</parameter></paramdef> + <paramdef>XtPointer <parameter>client_data</parameter></paramdef> +</funcprototype> +</funcsynopsis> + +<variablelist> + <varlistentry> + <term> + <emphasis remap='I'>app_context</emphasis> + </term> + <listitem> + <para> +Specifies the application context that identifies the application. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>proc</emphasis> + </term> + <listitem> + <para> +Specifies the procedure to be called when the application is idle. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>client_data</emphasis> + </term> + <listitem> + <para> +Specifies the argument passed to the specified procedure +when it is called. + </para> + </listitem> + </varlistentry> +</variablelist> + +<para> +The +<xref linkend='XtAppAddWorkProc' xrefstyle='select: title'/> +function adds the specified work procedure for the application identified +by <emphasis remap='I'>app_context</emphasis> +and returns an opaque unique identifier for this work procedure. +Multiple work procedures can be registered, +and the most recently added one is always the one that is called. +However, if a work procedure adds another work procedure, +the newly added one has lower priority than the current one. +</para> + +<para> +To remove a work procedure, either return +<function>True</function> +from the procedure when it is called or use +<xref linkend='XtRemoveWorkProc' xrefstyle='select: title'/> +outside of the procedure. +</para> + +<funcsynopsis id='XtRemoveWorkProc'> +<funcprototype> +<funcdef>void <function>XtRemoveWorkProc</function></funcdef> + <paramdef>XtWorkProcId <parameter>id</parameter></paramdef> +</funcprototype> +</funcsynopsis> + +<variablelist> + <varlistentry> + <term> + <emphasis remap='I'>id</emphasis> + </term> + <listitem> + <para> +Specifies which work procedure to remove. + </para> + </listitem> + </varlistentry> +</variablelist> + +<para> +The +<xref linkend='XtRemoveWorkProc' xrefstyle='select: title'/> +function explicitly removes the specified background work procedure. +</para> +</sect1> + +<sect1 id="X_Event_Filters"> +<title>X Event Filters</title> +<para> +The event manager provides filters that can be applied to +specific X events. +The filters, which screen out events that are redundant or are temporarily +unwanted, handle +pointer motion compression, +enter/leave compression, and +exposure compression. +</para> +<sect2 id="Pointer_Motion_Compression"> +<title>Pointer Motion Compression</title> +<para> +Widgets can have a hard time keeping up with a rapid stream of +pointer motion events. Furthermore, +they usually do not care about every motion event. To throw out +redundant motion events, the widget class field <emphasis remap='I'>compress_motion</emphasis> should be +<function>True</function>. +When a request for an event would return a motion event, +the Intrinsics check if there are any other motion events +for the same widget immediately +following the current one and, if so, skip all but the last of them. +</para> +</sect2> + +<sect2 id="Enter_Leave_Compression"> +<title>Enter/Leave Compression</title> +<para> +To throw out pairs of enter and leave events that have no intervening events, +as can happen when the user moves the pointer across a widget +without stopping in it, +the widget class field <emphasis remap='I'>compress_enterleave</emphasis> should be +<function>True</function>. +These enter and leave events are not delivered to the client +if they are found together in the input queue. +</para> +</sect2> + +<sect2 id="Exposure_Compression"> +<title>Exposure Compression</title> +<para> +Many widgets prefer to process a series of exposure events as a +single expose region rather than as individual rectangles. Widgets +with complex displays might use the expose region as a clip list +in a graphics context, and widgets with simple displays might +ignore the region entirely and redisplay their whole window or +might get the bounding box from the region and redisplay only that +rectangle. +</para> + +<para> +In either case, these widgets do not care about getting partial exposure events. +The <emphasis remap='I'>compress_exposure</emphasis> field in the widget class +structure specifies the type and number of exposure events that are +dispatched to the widget's expose procedure. This field must be +initialized to one of the following values: +</para> + +<literallayout > +#define XtExposeNoCompress ((XtEnum)False) +#define XtExposeCompressSeries ((XtEnum)True) +#define XtExposeCompressMultiple <implementation-defined> +#define XtExposeCompressMaximal <implementation-defined> +</literallayout> + +<para> +optionally ORed with any combination of the following flags (all with +implementation-defined values): +<function>XtExposeGraphicsExpose</function>, +<function>XtExposeGraphicsExposeMerged</function>, +<function>XtExposeNoExpose</function>, +and +<function>XtExposeNoRegion</function>. +</para> + +<para> +If the <emphasis remap='I'>compress_exposure</emphasis> field in the widget class structure does not +specify +<function>XtExposeNoCompress</function>, +the event manager calls the widget's expose procedure only +once for a series of exposure events. +In this case, all +<function>Expose</function> +or +<function>GraphicsExpose</function> +events are accumulated into a region. +When the final event is received, +the event manager replaces the rectangle in the event with the +bounding box for the region +and calls the widget's expose procedure, +passing the modified exposure event and (unless +<function>XtExposeNoRegion</function> +is specified) the region. +For more information on regions, see +<olink targetdoc='libX11' targetptr='Manipulating_Regions'>Section 16.5</olink> in +<olink targetdoc='libX11' targetptr='libX11'>Xlib — C Language X Interface.</olink>.) +</para> + +<para> +The values have the following interpretation: +</para> + +<para> +<function>XtExposeNoCompress</function> +</para> +<itemizedlist spacing='compact'> + <listitem> + <para> +No exposure compression is performed; every selected event is +individually dispatched to the expose procedure with a <emphasis remap='I'>region</emphasis> +argument of NULL. + </para> + </listitem> +</itemizedlist> +<para> +<function>XtExposeCompressSeries</function> +</para> +<itemizedlist spacing='compact'> + <listitem> + <para> +Each series of exposure events is coalesced into a single event, +which is dispatched +when an exposure event with count equal to zero is reached. + </para> + </listitem> +</itemizedlist> +<para> +<function>XtExposeCompressMultiple</function> +</para> +<itemizedlist spacing='compact'> + <listitem> + <para> +Consecutive series of exposure events are coalesced into a single +event, which is dispatched +when an exposure event with count equal to zero is reached and either +the event queue is empty or the next event is not an exposure event +for the same widget. + </para> + </listitem> +</itemizedlist> +<para> +<function>XtExposeCompressMaximal</function> +</para> +<itemizedlist spacing='compact'> + <listitem> + <para> +All expose series currently in the queue for the widget +are coalesced into a single +event without regard to intervening nonexposure events. If a +partial series is in the end of the queue, the Intrinsics will +block until the end of the series is received. + </para> + </listitem> +</itemizedlist> +<para> +The additional flags have the following meaning: +</para> + +<para> +<function>XtExposeGraphicsExpose</function> +</para> +<itemizedlist spacing='compact'> + <listitem> + <para> +Specifies that +<function>GraphicsExpose</function> +events are also to be dispatched to +the expose procedure. +<function>GraphicsExpose</function> +events are compressed, if specified, in the same manner as +<function>Expose</function> +events. + </para> + </listitem> +</itemizedlist> +<para> +<function>XtExposeGraphicsExposeMerged</function> +</para> +<itemizedlist spacing='compact'> + <listitem> + <para> +Specifies in the case of +<function>XtExposeCompressMultiple</function> +and +<function>XtExposeCompressMaximal</function> +that series of +<function>GraphicsExpose</function> +and +<function>Expose</function> +events are to be compressed together, with the final event type +determining the type of the event passed to the expose procedure. +If this flag is not set, then only series of the same event type +as the event at the head of the queue are coalesced. This flag +also implies +<function>XtExposeGraphicsExpose</function>. + </para> + </listitem> +</itemizedlist> +<para> +<function>XtExposeNoExpose</function> +</para> +<itemizedlist spacing='compact'> + <listitem> + <para> +Specifies that +<function>NoExpose</function> +events are also to be dispatched to the expose procedure. +<function>NoExpose</function> +events are never coalesced with +other exposure events or with each other. + </para> + </listitem> +</itemizedlist> +<para> +<function>XtExposeNoRegion</function> +</para> +<itemizedlist spacing='compact'> + <listitem> + <para> +Specifies that the final region argument passed to the expose +procedure is NULL. The rectangle in the event will still +contain bounding box information for the entire series of +compressed exposure events. This option saves processing time when the +region is not needed by the widget. + </para> + </listitem> +</itemizedlist> +</sect2> +</sect1> + +<sect1 id="Widget_Exposure_and_Visibility"> +<title>Widget Exposure and Visibility</title> +<para> +Every primitive widget and some composite widgets display data on the screen +by means of direct Xlib calls. +Widgets cannot simply write to the screen and forget what they have done. +They must keep enough state to redisplay the window or parts +of it if a portion is obscured and then reexposed. +</para> + +<sect2 id="Redisplay_of_a_Widget_The_expose_Procedure"> +<title>Redisplay of a Widget: The expose Procedure</title> +<para> +The expose procedure pointer in a widget class is of type +<xref linkend='XtExposeProc' xrefstyle='select: title'/>. +</para> + +<funcsynopsis id='XtExposeProc'> +<funcprototype> +<funcdef>typedef void <function>(*XtExposeProc)</function></funcdef> + <paramdef>Widget <parameter>w</parameter></paramdef> + <paramdef>XEvent *<parameter>event</parameter></paramdef> + <paramdef>Region <parameter>region</parameter></paramdef> +</funcprototype> +</funcsynopsis> + +<variablelist> + <varlistentry> + <term> + <emphasis remap='I'>w</emphasis> + </term> + <listitem> + <para> +Specifies the widget instance requiring redisplay. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>event</emphasis> + </term> + <listitem> + <para> +Specifies the exposure event giving the rectangle requiring redisplay. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>region</emphasis> + </term> + <listitem> + <para> +Specifies the union of all rectangles in this exposure sequence. + </para> + </listitem> + </varlistentry> +</variablelist> + +<para> +The redisplay of a widget upon exposure is the responsibility of the +expose procedure in the widget's class record. +If a widget has no display semantics, +it can specify NULL for the <emphasis remap='I'>expose</emphasis> field. +Many composite widgets serve only as containers for their children +and have no expose procedure. +</para> + +<note> +<para> +If the <emphasis remap='I'>expose</emphasis> procedure is NULL, +<xref linkend='XtRealizeWidget' xrefstyle='select: title'/> +fills in a default bit gravity of +<function>NorthWestGravity</function> +before it calls the widget's realize procedure. +</para> +</note> + +<para> +If the widget's <emphasis remap='I'>compress_exposure</emphasis> class field specifies +<function>XtExposeNoCompress</function> +or +<function>XtExposeNoRegion</function>, +or if the event type is +<function>NoExpose</function> +(see <xref linkend='Exposure_Compression' />), +<emphasis remap='I'>region</emphasis> is NULL. If +<function>XtExposeNoCompress</function> +is not specified and the event type is not +<function>NoExpose</function>, +the event is the final event in the compressed series +but <emphasis remap='I'>x</emphasis>, <emphasis remap='I'>y</emphasis>, <emphasis remap='I'>width</emphasis>, and <emphasis remap='I'>height</emphasis> contain +the bounding box for all the compressed events. +The region is created and destroyed by the Intrinsics, but +the widget is permitted to modify the region contents. +</para> + +<para> +A small simple widget (for example, Label) can ignore the bounding box +information in the event and redisplay the entire window. +A more complicated widget (for example, Text) can use the bounding box +information to minimize the amount of calculation and redisplay it does. +A very complex widget uses the region as a clip list in a GC and +ignores the event information. +The expose procedure is not chained and is therefore +responsible for exposure of all superclass data +as well as its own. +</para> + +<para> +However, +it often is possible to anticipate the display needs of several levels +of subclassing. +For example, rather than implement separate display procedures for +the widgets Label, Pushbutton, and Toggle, +you could write a single display routine in Label that uses display state +fields like +</para> +<literallayout > +Boolean invert; +Boolean highlight; +Dimension highlight_width; +</literallayout> +<para> +Label would have <emphasis remap='I'>invert</emphasis> and <emphasis remap='I'>highlight</emphasis> always +<function>False</function> +and <emphasis remap='I'>highlight_width</emphasis> zero. +Pushbutton would dynamically set <emphasis remap='I'>highlight</emphasis> and <emphasis remap='I'>highlight_width</emphasis>, +but it would leave <emphasis remap='I'>invert</emphasis> always +<function>False</function>. +Finally, Toggle would dynamically set all three. +In this case, +the expose procedures for Pushbutton and Toggle inherit +their superclass's expose procedure; +see <xref linkend='Inheritance_of_Superclass_Operations' />. +</para> +</sect2> + +<sect2 id="Widget_Visibility"> +<title>Widget Visibility</title> +<para> +Some widgets may use substantial computing resources to produce the +data they will display. +However, this effort is wasted if the widget is not actually visible +on the screen, that is, if the widget is obscured by another application +or is iconified. +</para> + +<para> +The <emphasis remap='I'>visible</emphasis> field in the +core +widget structure provides a hint to the widget that it need not compute +display data. +This field is guaranteed to be +<function>True</function> +by the time an +exposure +event is processed if any part of the widget is visible, +but is +<function>False</function> +if the widget is fully obscured. +</para> + +<para> +Widgets can use or ignore the <emphasis remap='I'>visible</emphasis> hint. +If they ignore it, +they should have <emphasis remap='I'>visible_interest</emphasis> in their widget class record set +<function>False</function>. +In such cases, +the <emphasis remap='I'>visible</emphasis> field is initialized +<function>True</function> +and never changes. +If <emphasis remap='I'>visible_interest</emphasis> is +<function>True</function>, +the event manager asks for +<function>VisibilityNotify</function> +events for the widget and sets <emphasis remap='I'>visible</emphasis> to +<function>True</function> +on +<function>VisibilityUnobscured</function> +or +<function>VisibilityPartiallyObscured</function> +events and +<function>False</function> +on +<function>VisibilityFullyObscured</function> +events. +</para> +</sect2> +</sect1> + +<sect1 id="X_Event_Handlers"> +<title>X Event Handlers</title> +<para> +Event handlers are procedures called when specified events +occur in a widget. +Most widgets need not use event handlers explicitly. +Instead, they use the Intrinsics translation manager. +Event handler procedure pointers are of the type +<xref linkend='XtEventHandler' xrefstyle='select: title'/>. +</para> + +<funcsynopsis id='XtEventHandler'> +<funcprototype> +<funcdef>typedef void <function>(*XtEventHandler)</function></funcdef> + + <paramdef>Widget <parameter>w</parameter></paramdef> + <paramdef>XtPointer <parameter>client_data</parameter></paramdef> + <paramdef>XEvent *<parameter>event</parameter></paramdef> + <paramdef>Boolean *<parameter>continue_to_dispatch</parameter></paramdef> +</funcprototype> +</funcsynopsis> + +<variablelist> + <varlistentry> + <term> + <emphasis remap='I'>w</emphasis> + </term> + <listitem> + <para> +Specifies the widget for which the event arrived. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>client_data</emphasis> + </term> + <listitem> + <para> +Specifies any client-specific information registered with the event handler. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>event</emphasis> + </term> + <listitem> + <para> +Specifies the triggering event. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>continue_to_dispatch</emphasis> + </term> + <listitem> + <para> +Specifies whether the remaining event +handlers registered for the current event +should be called. + </para> + </listitem> + </varlistentry> +</variablelist> + +<para> +After receiving an event and before calling any event handlers, the +Boolean pointed to by <emphasis remap='I'>continue_to_dispatch</emphasis> is initialized to +<function>True</function>. +When an event handler is called, it may decide that further processing +of the event is not desirable and may store +<function>False</function> +in this Boolean, in +which case any handlers remaining to be called for the event are +ignored. +</para> + +<para> +The circumstances under which the Intrinsics may add event handlers +to a widget are currently implementation-dependent. Clients must +therefore be aware that storing +<function>False</function> +into the <emphasis remap='I'>continue_to_dispatch</emphasis> argument can lead to portability problems. +</para> +<sect2 id="Event_Handlers_That_Select_Events"> +<title>Event Handlers That Select Events</title> +<para> +To register an event handler procedure with the dispatch mechanism, use +<xref linkend='XtAddEventHandler' xrefstyle='select: title'/>. +</para> + +<funcsynopsis id='XtAddEventHandler'> +<funcprototype> +<funcdef>void <function>XtAddEventHandler</function></funcdef> + <paramdef>Widget <parameter>w</parameter></paramdef> + <paramdef>EventMask <parameter>event_mask</parameter></paramdef> + <paramdef>Boolean <parameter>nonmaskable</parameter></paramdef> + <paramdef>XtEventHandler <parameter>proc</parameter></paramdef> + <paramdef>XtPointer <parameter>client_data</parameter></paramdef> +</funcprototype> +</funcsynopsis> + +<variablelist> + <varlistentry> + <term> + <emphasis remap='I'>w</emphasis> + </term> + <listitem> + <para> +Specifies the widget for which this event handler is being registered. Must be of class Core or any subclass thereof. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>event_mask</emphasis> + </term> + <listitem> + <para> +Specifies the event mask for which to call this procedure. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>nonmaskable</emphasis> + </term> + <listitem> + <para> +Specifies whether this procedure should be +called on the nonmaskable events +<function>( GraphicsExpose</function>, +<function>NoExpose</function>, +<function>SelectionClear</function>, +<function>SelectionRequest</function>, +<function>SelectionNotify</function>, +<function>ClientMessage</function>, +and +<function>MappingNotify ).</function> + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>proc</emphasis> + </term> + <listitem> + <para> +Specifies the procedure to be called. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>client_data</emphasis> + </term> + <listitem> + <para> +Specifies additional data to be passed to the event handler. + </para> + </listitem> + </varlistentry> +</variablelist> + +<para> +The +<xref linkend='XtAddEventHandler' xrefstyle='select: title'/> +function registers a procedure with the dispatch mechanism that is +to be called when an event that matches the mask occurs on the specified +widget. +Each widget has a single registered event handler list, which will +contain any procedure/client_data pair exactly once regardless of +the manner in which it is registered. +If the procedure is already registered with the same <emphasis remap='I'>client_data</emphasis> +value, +the specified mask augments the existing mask. +If the widget is realized, +<xref linkend='XtAddEventHandler' xrefstyle='select: title'/> +calls +<function>XSelectInput</function>, +if necessary. +The order in which this procedure is called relative to other handlers +registered for the same event is not defined. +</para> + +<para> +To remove a previously registered event handler, use +<xref linkend='XtRemoveEventHandler' xrefstyle='select: title'/>. +</para> + +<funcsynopsis id='XtRemoveEventHandler'> +<funcprototype> +<funcdef>void <function>XtRemoveEventHandler</function></funcdef> + <paramdef>Widget <parameter>w</parameter></paramdef> + <paramdef>EventMask <parameter>event_mask</parameter></paramdef> + <paramdef>Boolean <parameter>nonmaskable</parameter></paramdef> + <paramdef>XtEventHandler <parameter>proc</parameter></paramdef> + <paramdef>XtPointer <parameter>client_data</parameter></paramdef> +</funcprototype> +</funcsynopsis> + +<variablelist> + <varlistentry> + <term> + <emphasis remap='I'>w</emphasis> + </term> + <listitem> + <para> +Specifies the widget for which this procedure is registered. Must be of class Core or any subclass thereof. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>event_mask</emphasis> + </term> + <listitem> + <para> +Specifies the event mask for which to unregister this procedure. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>nonmaskable</emphasis> + </term> + <listitem> + <para> +Specifies whether this procedure should be +removed on the nonmaskable events +<function>( GraphicsExpose</function>, +<function>NoExpose</function>, +<function>SelectionClear</function>, +<function>SelectionRequest</function>, +<function>SelectionNotify</function>, +<function>ClientMessage</function>, +and +<function>MappingNotify ).</function> + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>proc</emphasis> + </term> + <listitem> + <para> +Specifies the procedure to be removed. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>client_data</emphasis> + </term> + <listitem> + <para> +Specifies the registered client data. + </para> + </listitem> + </varlistentry> +</variablelist> + +<para> +The +<xref linkend='XtRemoveEventHandler' xrefstyle='select: title'/> +function unregisters an event handler registered with +<xref linkend='XtAddEventHandler' xrefstyle='select: title'/> +or +<xref linkend='XtInsertEventHandler' xrefstyle='select: title'/> +for the specified events. +The request is ignored if <emphasis remap='I'>client_data</emphasis> does not match the value given +when the handler was registered. +If the widget is realized and no other event handler requires the event, +<xref linkend='XtRemoveEventHandler' xrefstyle='select: title'/> +calls +<function>XSelectInput</function>. +If the specified procedure has not been registered +or if it has been registered with a different value of <emphasis remap='I'>client_data</emphasis>, +<xref linkend='XtRemoveEventHandler' xrefstyle='select: title'/> +returns without reporting an error. +</para> + +<para> +To stop a procedure registered with +<xref linkend='XtAddEventHandler' xrefstyle='select: title'/> +or +<xref linkend='XtInsertEventHandler' xrefstyle='select: title'/> +from receiving all selected events, call +<xref linkend='XtRemoveEventHandler' xrefstyle='select: title'/> +with an <emphasis remap='I'>event_mask</emphasis> of +<function>XtAllEvents</function> +and <emphasis remap='I'>nonmaskable</emphasis> +<function>True</function>. +The procedure will continue to receive any events +that have been specified in calls to +<xref linkend='XtAddRawEventHandler' xrefstyle='select: title'/> +or +<xref linkend='XtInsertRawEventHandler' xrefstyle='select: title'/>. +</para> + +<para> +To register an event handler procedure that receives events before or +after all previously registered event handlers, use +<xref linkend='XtInsertEventHandler' xrefstyle='select: title'/>. +</para> +<literallayout > +typedef enum {XtListHead, XtListTail} XtListPosition; +</literallayout> + +<funcsynopsis id='XtInsertEventHandler'> +<funcprototype> +<funcdef>void <function>XtInsertEventHandler</function></funcdef> + <paramdef>Widget <parameter>w</parameter></paramdef> + <paramdef>EventMask <parameter>event_mask</parameter></paramdef> + <paramdef>Boolean <parameter>nonmaskable</parameter></paramdef> + <paramdef>XtEventHandler <parameter>proc</parameter></paramdef> + <paramdef>XtPointer <parameter>client_data</parameter></paramdef> + <paramdef>XtListPosition <parameter>position</parameter></paramdef> +</funcprototype> +</funcsynopsis> + +<variablelist> + <varlistentry> + <term> + <emphasis remap='I'>w</emphasis> + </term> + <listitem> + <para> +Specifies the widget for which this event handler is being registered. Must be of class Core or any subclass thereof. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>event_mask</emphasis> + </term> + <listitem> + <para> +Specifies the event mask for which to call this procedure. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>nonmaskable</emphasis> + </term> + <listitem> + <para> +Specifies whether this procedure should be +called on the nonmaskable events +<function>( GraphicsExpose</function>, +<function>NoExpose</function>, +<function>SelectionClear</function>, +<function>SelectionRequest</function>, +<function>SelectionNotify</function>, +<function>ClientMessage</function>, +and +<function>MappingNotify ).</function> + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>proc</emphasis> + </term> + <listitem> + <para> +Specifies the procedure to be called. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>client_data</emphasis> + </term> + <listitem> + <para> +Specifies additional data to be passed to the client's event handler. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>position</emphasis> + </term> + <listitem> + <para> +Specifies when the event handler is to be called +relative to other previously registered handlers. + </para> + </listitem> + </varlistentry> +</variablelist> + +<para> +<xref linkend='XtInsertEventHandler' xrefstyle='select: title'/> +is identical to +<xref linkend='XtAddEventHandler' xrefstyle='select: title'/> +with the additional <emphasis remap='I'>position</emphasis> argument. If <emphasis remap='I'>position</emphasis> is +<function>XtListHead</function>, +the event +handler is registered so that it is called before any event +handlers that were previously registered for the same widget. If +<emphasis remap='I'>position</emphasis> is +<function>XtListTail</function>, +the event handler is registered to be called +after any previously registered event handlers. If the procedure is +already registered with the same <emphasis remap='I'>client_data</emphasis> value, the specified mask +augments the existing mask and the procedure is repositioned in +the list. +</para> +</sect2> + +<sect2 id="Event_Handlers_That_Do_Not_Select_Events"> +<title>Event Handlers That Do Not Select Events</title> +<para> +On occasion, +clients need to register an event handler procedure with the +dispatch mechanism without explicitly +causing the X server to select for that event. +To do this, use +<xref linkend='XtAddRawEventHandler' xrefstyle='select: title'/>. +</para> + +<funcsynopsis id='XtAddRawEventHandler'> +<funcprototype> +<funcdef>void <function>XtAddRawEventHandler</function></funcdef> + <paramdef>Widget <parameter>w</parameter></paramdef> + <paramdef>EventMask <parameter>event_mask</parameter></paramdef> + <paramdef>Boolean <parameter>nonmaskable</parameter></paramdef> + <paramdef>XtEventHandler <parameter>proc</parameter></paramdef> + <paramdef>XtPointer <parameter>client_data</parameter></paramdef> +</funcprototype> +</funcsynopsis> + +<variablelist> + <varlistentry> + <term> + <emphasis remap='I'>w</emphasis> + </term> + <listitem> + <para> +Specifies the widget for which this event handler is being registered. Must be of class Core or any subclass thereof. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>event_mask</emphasis> + </term> + <listitem> + <para> +Specifies the event mask for which to call this procedure. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>nonmaskable</emphasis> + </term> + <listitem> + <para> +Specifies whether this procedure should be +called on the nonmaskable events +<function>( GraphicsExpose</function>, +<function>NoExpose</function>, +<function>SelectionClear</function>, +<function>SelectionRequest</function>, +<function>SelectionNotify</function>, +<function>ClientMessage</function>, +and +<function>MappingNotify ).</function> + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>proc</emphasis> + </term> + <listitem> + <para> +Specifies the procedure to be called. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>client_data</emphasis> + </term> + <listitem> + <para> +Specifies additional data to be passed to the client's event handler. + </para> + </listitem> + </varlistentry> +</variablelist> + +<para> +The +<xref linkend='XtAddRawEventHandler' xrefstyle='select: title'/> +function is similar to +<xref linkend='XtAddEventHandler' xrefstyle='select: title'/> +except that it does not affect the widget's event mask and never causes an +<function>XSelectInput</function> +for its events. +Note that the widget might already have those mask bits set +because of other nonraw event handlers registered on it. +If the procedure is already registered with the same <emphasis remap='I'>client_data</emphasis>, +the specified mask augments the existing mask. +The order in which this procedure is called relative to other handlers +registered for the same event is not defined. +</para> + +<para> +To remove a previously registered raw event handler, use +<xref linkend='XtRemoveRawEventHandler' xrefstyle='select: title'/>. +</para> + +<funcsynopsis id='XtRemoveRawEventHandler'> +<funcprototype> +<funcdef>void <function>XtRemoveRawEventHandler</function></funcdef> + <paramdef>Widget <parameter>w</parameter></paramdef> + <paramdef>EventMask <parameter>event_mask</parameter></paramdef> + <paramdef>Boolean <parameter>nonmaskable</parameter></paramdef> + <paramdef>XtEventHandler <parameter>proc</parameter></paramdef> + <paramdef>XtPointer <parameter>client_data</parameter></paramdef> +</funcprototype> +</funcsynopsis> + +<variablelist> + <varlistentry> + <term> + <emphasis remap='I'>w</emphasis> + </term> + <listitem> + <para> +Specifies the widget for which this procedure is registered. Must be of class Core or any subclass thereof. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>event_mask</emphasis> + </term> + <listitem> + <para> +Specifies the event mask for which to unregister this procedure. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>nonmaskable</emphasis> + </term> + <listitem> + <para> +Specifies whether this procedure should be +removed on the nonmaskable events +<function>( GraphicsExpose</function>, +<function>NoExpose</function>, +<function>SelectionClear</function>, +<function>SelectionRequest</function>, +<function>SelectionNotify</function>, +<function>ClientMessage</function>, +and +<function>MappingNotify ).</function> + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>proc</emphasis> + </term> + <listitem> + <para> +Specifies the procedure to be registered. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>client_data</emphasis> + </term> + <listitem> + <para> +Specifies the registered client data. + </para> + </listitem> + </varlistentry> +</variablelist> + +<para> +The +<xref linkend='XtRemoveRawEventHandler' xrefstyle='select: title'/> +function unregisters an event handler registered with +<xref linkend='XtAddRawEventHandler' xrefstyle='select: title'/> +or +<xref linkend='XtInsertRawEventHandler' xrefstyle='select: title'/> +for the specified events without changing +the window event mask. +The request is ignored if <emphasis remap='I'>client_data</emphasis> does not match the value given +when the handler was registered. +If the specified procedure has not been registered +or if it has been registered with a different value of <emphasis remap='I'>client_data</emphasis>, +<xref linkend='XtRemoveRawEventHandler' xrefstyle='select: title'/> +returns without reporting an error. +</para> + +<para> +To stop a procedure +registered with +<xref linkend='XtAddRawEventHandler' xrefstyle='select: title'/> +or +<xref linkend='XtInsertRawEventHandler' xrefstyle='select: title'/> +from receiving all nonselected events, call +<xref linkend='XtRemoveRawEventHandler' xrefstyle='select: title'/> +with an <emphasis remap='I'>event_mask</emphasis> of +<function>XtAllEvents</function> +and <emphasis remap='I'>nonmaskable</emphasis> +<function>True</function>. +The procedure +will continue to receive any events that have been specified in calls to +<xref linkend='XtAddEventHandler' xrefstyle='select: title'/> +or +<xref linkend='XtInsertEventHandler' xrefstyle='select: title'/>. +</para> + +<para> +To register an event handler procedure that receives events before or +after all previously registered event handlers without selecting for +the events, use +<xref linkend='XtInsertRawEventHandler' xrefstyle='select: title'/>. +</para> + +<funcsynopsis id='XtInsertRawEventHandler'> +<funcprototype> +<funcdef>void <function>XtInsertRawEventHandler</function></funcdef> + <paramdef>Widget <parameter>w</parameter></paramdef> + <paramdef>EventMask <parameter>event_mask</parameter></paramdef> + <paramdef>Boolean <parameter>nonmaskable</parameter></paramdef> + <paramdef>XtEventHandler <parameter>proc</parameter></paramdef> + <paramdef>XtPointer <parameter>client_data</parameter></paramdef> + <paramdef>XtListPosition <parameter>position</parameter></paramdef> +</funcprototype> +</funcsynopsis> + +<variablelist> + <varlistentry> + <term> + <emphasis remap='I'>w</emphasis> + </term> + <listitem> + <para> +Specifies the widget for which this event handler is being registered. Must be of class Core or any subclass thereof. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>event_mask</emphasis> + </term> + <listitem> + <para> +Specifies the event mask for which to call this procedure. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>nonmaskable</emphasis> + </term> + <listitem> + <para> +Specifies whether this procedure should be +called on the nonmaskable events +<function>( GraphicsExpose</function>, +<function>NoExpose</function>, +<function>SelectionClear</function>, +<function>SelectionRequest</function>, +<function>SelectionNotify</function>, +<function>ClientMessage</function>, +and +<function>MappingNotify ).</function> + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>proc</emphasis> + </term> + <listitem> + <para> +Specifies the procedure to be registered. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>client_data</emphasis> + </term> + <listitem> + <para> +Specifies additional data to be passed to the client's event handler. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>position</emphasis> + </term> + <listitem> + <para> +Specifies when the event handler is to be called +relative to other previously registered handlers. + </para> + </listitem> + </varlistentry> +</variablelist> + +<para> +The +<xref linkend='XtInsertRawEventHandler' xrefstyle='select: title'/> +function is similar to +<xref linkend='XtInsertEventHandler' xrefstyle='select: title'/> +except that it does not modify the widget's event +mask and never causes an +<function>XSelectInput</function> +for the specified events. If +the procedure is already registered with the same <emphasis remap='I'>client_data</emphasis> +value, the +specified mask augments the existing mask and the procedure is +repositioned in the list. +</para> +</sect2> + +<sect2 id="Current_Event_Mask"> +<title>Current Event Mask</title> +<para> +To retrieve the event mask for a given widget, use +<xref linkend='XtBuildEventMask' xrefstyle='select: title'/>. +</para> + +<funcsynopsis id='XtBuildEventMask'> +<funcprototype> +<funcdef>EventMask <function>XtBuildEventMask</function></funcdef> + <paramdef>Widget <parameter>w</parameter></paramdef> +</funcprototype> +</funcsynopsis> + +<variablelist> + <varlistentry> + <term> + <emphasis remap='I'>w</emphasis> + </term> + <listitem> + <para> +Specifies the widget. Must be of class Core or any subclass thereof. + </para> + </listitem> + </varlistentry> +</variablelist> + +<para> +The +<xref linkend='XtBuildEventMask' xrefstyle='select: title'/> +function returns the event mask representing the logical OR +of all event masks for event handlers registered on the widget with +<xref linkend='XtAddEventHandler' xrefstyle='select: title'/> +and +<xref linkend='XtInsertEventHandler' xrefstyle='select: title'/> +and all event translations, including accelerators, +installed on the widget. +This is the same event mask stored into the +<function>XSetWindowAttributes</function> +structure by +<xref linkend='XtRealizeWidget' xrefstyle='select: title'/> +and sent to the server when event handlers and translations are installed or +removed on the realized widget. +</para> +</sect2> + +<sect2 id="Event_Handlers_for_X_Protocol_Extensions"> +<title>Event Handlers for X11 Protocol Extensions</title> +<para> +To register an event handler procedure with the Intrinsics dispatch +mechanism according to an event type, use +<xref linkend='XtInsertEventTypeHandler' xrefstyle='select: title'/>. +</para> + +<funcsynopsis id='XtInsertEventTypeHandler'> +<funcprototype> +<funcdef>void <function>XtInsertEventTypeHandler</function></funcdef> + <paramdef>Widget <parameter>widget</parameter></paramdef> + <paramdef>int <parameter>event_type</parameter></paramdef> + <paramdef>XtPointer <parameter>select_data</parameter></paramdef> + <paramdef>XtEventHandler <parameter>proc</parameter></paramdef> + <paramdef>XtPointer <parameter>client_data</parameter></paramdef> + <paramdef>XtListPosition <parameter>position</parameter></paramdef> +</funcprototype> +</funcsynopsis> + +<variablelist> + <varlistentry> + <term> + <emphasis remap='I'>widget</emphasis> + </term> + <listitem> + <para> +Specifies the widget for which this event handler is being registered. Must be of class Core or any subclass thereof. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>event_type</emphasis> + </term> + <listitem> + <para> +Specifies the event type for which to call this event handler. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>select_data</emphasis> + </term> + <listitem> + <para> +Specifies data used to request events of the specified type from the server, +or NULL. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>proc</emphasis> + </term> + <listitem> + <para> +Specifies the event handler to be called. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>client_data</emphasis> + </term> + <listitem> + <para> +Specifies additional data to be passed to the event handler. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>position</emphasis> + </term> + <listitem> + <para> +Specifies when the event handler is to be called relative to other +previously registered handlers. + </para> + </listitem> + </varlistentry> +</variablelist> + +<para> +<xref linkend='XtInsertEventTypeHandler' xrefstyle='select: title'/> +registers a procedure with the +dispatch mechanism that is to be called when an event that matches the +specified <emphasis remap='I'>event_type</emphasis> is dispatched to the specified <emphasis remap='I'>widget</emphasis>. +</para> + +<para> +If <emphasis remap='I'>event_type</emphasis> specifies one of the core X protocol events, then +<emphasis remap='I'>select_data</emphasis> must be a pointer to a value of type +<function>EventMask</function>, +indicating +the event mask to be used to select for the desired event. This event +mask is included in the value returned by +<xref linkend='XtBuildEventMask' xrefstyle='select: title'/>. +If the widget is realized, +<xref linkend='XtInsertEventTypeHandler' xrefstyle='select: title'/> +calls +<function>XSelectInput</function> +if necessary. Specifying NULL for <emphasis remap='I'>select_data</emphasis> is equivalent to +specifying a pointer to an event mask containing 0. This is similar +to the +<xref linkend='XtInsertRawEventHandler' xrefstyle='select: title'/> +function. +</para> + +<para> +If <emphasis remap='I'>event_type</emphasis> specifies an extension event type, then the semantics of +the data pointed to by <emphasis remap='I'>select_data</emphasis> are defined by the extension +selector registered for the specified event type. +</para> + +<para> +In either case the Intrinsics are not required to copy the data +pointed to by <emphasis remap='I'>select_data</emphasis>, so the caller must ensure that it remains +valid as long as the event handler remains registered with this value +of <emphasis remap='I'>select_data</emphasis>. +</para> + +<para> +The <emphasis remap='I'>position</emphasis> argument allows the client to control the order of +invocation of event handlers registered for the same event type. If +the client does not care about the order, it should normally specify +<function>XtListTail</function>, +which registers this event handler after any previously +registered handlers for this event type. +</para> + +<para> +Each widget has a single registered event handler list, which will +contain any procedure/client_data pair exactly once if it is +registered with +<xref linkend='XtInsertEventTypeHandler' xrefstyle='select: title'/>, +regardless of the manner +in which it is registered and regardless of the value(s) +of <emphasis remap='I'>select_data</emphasis>. If the procedure is already registered with the +same <emphasis remap='I'>client_data</emphasis> value, the specified mask augments the existing +mask and the procedure is repositioned in the list. +</para> + +<para> +To remove an event handler registered with +<xref linkend='XtInsertEventTypeHandler' xrefstyle='select: title'/>, +use +<xref linkend='XtRemoveEventTypeHandler' xrefstyle='select: title'/>. +</para> + +<funcsynopsis id='XtRemoveEventTypeHandler'> +<funcprototype> +<funcdef>void <function>XtRemoveEventTypeHandler</function></funcdef> + <paramdef>Widget <parameter>widget</parameter></paramdef> + <paramdef>int <parameter>event_type</parameter></paramdef> + <paramdef>XtPointer <parameter>select_data</parameter></paramdef> + <paramdef>XtEventHandler <parameter>proc</parameter></paramdef> + <paramdef>XtPointer <parameter>client_data</parameter></paramdef> +</funcprototype> +</funcsynopsis> + +<variablelist> + <varlistentry> + <term> + <emphasis remap='I'>widget</emphasis> + </term> + <listitem> + <para> +Specifies the widget for which the event handler was registered. Must be of class Core or any subclass thereof. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>event_type</emphasis> + </term> + <listitem> + <para> +Specifies the event type for which the handler was registered. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>select_data</emphasis> + </term> + <listitem> + <para> +Specifies data used to deselect events of the specified type +from the server, or NULL. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>proc</emphasis> + </term> + <listitem> + <para> +Specifies the event handler to be removed. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>client_data</emphasis> + </term> + <listitem> + <para> +Specifies the additional client data with which the procedure was registered. + </para> + </listitem> + </varlistentry> +</variablelist> + +<para> +The +<xref linkend='XtRemoveEventTypeHandler' xrefstyle='select: title'/> +function unregisters an event handler +registered with +<xref linkend='XtInsertEventTypeHandler' xrefstyle='select: title'/> +for the specified event type. +The request is ignored if <emphasis remap='I'>client_data</emphasis> does not match the value given +when the handler was registered. +</para> + +<para> +If <emphasis remap='I'>event_type</emphasis> specifies one of the core X protocol events, +<emphasis remap='I'>select_data</emphasis> must be a pointer to a value of type +<function>EventMask, indicating the event</function> +mask to be used to deselect for the appropriate event. If the widget +is realized, +<xref linkend='XtRemoveEventTypeHandler' xrefstyle='select: title'/> +calls +<function>XSelectInput</function> +if necessary. +Specifying NULL for <emphasis remap='I'>select_data</emphasis> is equivalent to specifying a pointer +to an event mask containing 0. This is similar to the +<xref linkend='XtRemoveRawEventHandler' xrefstyle='select: title'/> +function. +</para> + +<para> +If <emphasis remap='I'>event_type</emphasis> specifies an extension event type, then the semantics of +the data pointed to by <emphasis remap='I'>select_data</emphasis> are defined by the extension +selector registered for the specified event type. +</para> + +<para> +To register a procedure to select extension events for a widget, use +<xref linkend='XtRegisterExtensionSelector' xrefstyle='select: title'/>. +</para> + +<funcsynopsis id='XtRegisterExtensionSelector'> +<funcprototype> +<funcdef>void <function>XtRegisterExtensionSelector</function></funcdef> + <paramdef>Display <parameter>*display</parameter></paramdef> + <paramdef>int <parameter>min_event_type</parameter></paramdef> + <paramdef>int <parameter>max_event_type</parameter></paramdef> + <paramdef>XtExtensionSelectProc <parameter>proc</parameter></paramdef> + <paramdef>XtPointer <parameter>client_data</parameter></paramdef> +</funcprototype> +</funcsynopsis> + +<variablelist> + <varlistentry> + <term> + <emphasis remap='I'>display</emphasis> + </term> + <listitem> + <para> +Specifies the display for which the extension selector is to be registered. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>min_event_type</emphasis> + </term> + <listitem> + <para></para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>max_event_type</emphasis> + </term> + <listitem> + <para> +Specifies the range of event types for the extension. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>proc</emphasis> + </term> + <listitem> + <para> +Specifies the extension selector procedure. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>client_data</emphasis> + </term> + <listitem> + <para> +Specifies additional data to be passed to the extension selector. + </para> + </listitem> + </varlistentry> +</variablelist> + +<para> +The +<xref linkend='XtRegisterExtensionSelector' xrefstyle='select: title'/> +function registers a procedure to arrange +for the delivery of extension events to widgets. +</para> + +<para> +If <emphasis remap='I'>min_event_type</emphasis> and <emphasis remap='I'>max_event_type</emphasis> match the parameters +to a previous call to +<xref linkend='XtRegisterExtensionSelector' xrefstyle='select: title'/> +for the same <emphasis remap='I'>display</emphasis>, then <emphasis remap='I'>proc</emphasis> and <emphasis remap='I'>client_data</emphasis> +replace the previously +registered values. If the range specified by <emphasis remap='I'>min_event_type</emphasis> +and <emphasis remap='I'>max_event_type</emphasis> overlaps the range of the parameters to a +previous call for the same display in any other way, an error results. +</para> + +<para> +When a widget is realized, +after the <emphasis remap='I'>core.realize</emphasis> method is called, +the Intrinsics check to see if any event +handler specifies an event type within the range of a registered +extension selector. If so, the Intrinsics call each such selector. +If an event type handler is added or removed, the Intrinsics check to +see if the event type falls within the range of a registered extension +selector, and if it does, calls the selector. In either case the Intrinsics +pass a list of all the widget's event types that are within the +selector's range. The corresponding select data are also passed. The +selector is responsible for enabling the delivery of extension events +required by the widget. +</para> + +<para> +An extension selector is of type +<xref linkend='XtExtensionSelectProc' xrefstyle='select: title'/>. +</para> + +<funcsynopsis id='XtExtensionSelectProc'> +<funcprototype> +<funcdef>typedef void <function>(*XtExtensionSelectProc)</function></funcdef> + + <paramdef>Widget <parameter>widget</parameter></paramdef> + <paramdef>int *<parameter>event_types</parameter></paramdef> + <paramdef>XtPointer *<parameter>select_data</parameter></paramdef> + <paramdef>int <parameter>count</parameter></paramdef> + <paramdef>XtPointer <parameter>client_data</parameter></paramdef> +</funcprototype> +</funcsynopsis> + +<variablelist> + <varlistentry> + <term> + <emphasis remap='I'>widget</emphasis> + </term> + <listitem> + <para> +Specifies the widget that is being realized or is having +an event handler added or removed. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>event_types</emphasis> + </term> + <listitem> + <para> +Specifies a list of event types that the widget has +registered event handlers for. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>select_data</emphasis> + </term> + <listitem> + <para> +Specifies a list of the select_data parameters specified in +<xref linkend='XtInsertEventTypeHandler' xrefstyle='select: title'/>. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>count</emphasis> + </term> + <listitem> + <para> +Specifies the number of entries in the <emphasis remap='I'>event_types</emphasis> and <emphasis remap='I'>select_data</emphasis> +lists. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>client_data</emphasis> + </term> + <listitem> + <para> +Specifies the additional client data with which the procedure was registered. + </para> + </listitem> + </varlistentry> +</variablelist> + +<para> +The <emphasis remap='I'>event_types</emphasis> and <emphasis remap='I'>select_data</emphasis> lists will always have the +same number of elements, specified by <emphasis remap='I'>count</emphasis>. +Each event type/select data pair represents one call to +<xref linkend='XtInsertEventTypeHandler' xrefstyle='select: title'/>. +</para> + +<para> +To register a procedure to dispatch events of a specific type within +<xref linkend='XtDispatchEvent' xrefstyle='select: title'/>, +use +<xref linkend='XtSetEventDispatcher' xrefstyle='select: title'/>. +</para> + +<funcsynopsis id='XtSetEventDispatcher'> +<funcprototype> +<funcdef>XtEventDispatchProc <function>XtSetEventDispatcher</function></funcdef> + <paramdef>Display *<parameter>display</parameter></paramdef> + <paramdef>int <parameter>event_type</parameter></paramdef> + <paramdef>XtEventDispatchProc <parameter>proc</parameter></paramdef> +</funcprototype> +</funcsynopsis> + +<variablelist> + <varlistentry> + <term> + <emphasis remap='I'>display</emphasis> + </term> + <listitem> + <para> +Specifies the display for which the event dispatcher is to be registered. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>event_type</emphasis> + </term> + <listitem> + <para> +Specifies the event type for which the dispatcher should be invoked. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>proc</emphasis> + </term> + <listitem> + <para> +Specifies the event dispatcher procedure. + </para> + </listitem> + </varlistentry> +</variablelist> + +<para> +The +<xref linkend='XtSetEventDispatcher' xrefstyle='select: title'/> +function registers the event dispatcher procedure specified by <emphasis remap='I'>proc</emphasis> +for events with the type <emphasis remap='I'>event_type</emphasis>. The previously registered +dispatcher (or the default dispatcher if there was no previously registered +dispatcher) is returned. If <emphasis remap='I'>proc</emphasis> is NULL, the default procedure is +restored for the specified type. +</para> + +<para> +In the future, when +<xref linkend='XtDispatchEvent' xrefstyle='select: title'/> +is called with an event type of <emphasis remap='I'>event_type</emphasis>, the specified <emphasis remap='I'>proc</emphasis> +(or the default dispatcher) is invoked to determine a widget +to which to dispatch the event. +</para> + +<para> +The default dispatcher handles the Intrinsics modal cascade and keyboard +focus mechanisms, handles the semantics of <emphasis remap='I'>compress_enterleave</emphasis> +and <emphasis remap='I'>compress_motion</emphasis>, and discards all extension events. +</para> + +<para> +An event dispatcher procedure pointer is of type +<xref linkend='XtEventDispatchProc' xrefstyle='select: title'/>. +</para> + +<funcsynopsis id='XtEventDispatchProc'> +<funcprototype> +<funcdef>typedef Boolean <function>(*XtEventDispatchProc)</function></funcdef> + <paramdef>XEvent *<parameter>event</parameter></paramdef> +</funcprototype> +</funcsynopsis> + +<variablelist> + <varlistentry> + <term> + <emphasis remap='I'>event</emphasis> + </term> + <listitem> + <para> +Passes the event to be dispatched. + </para> + </listitem> + </varlistentry> +</variablelist> + +<para> +The event dispatcher procedure should determine whether this event is of +a type that should be dispatched to a widget. +</para> + +<para> +If the event should be dispatched to a widget, the event dispatcher +procedure should determine the appropriate widget to receive the +event, call +<function>XFilterEvent</function> +with the window of this widget, or +<function>None</function> +if the event is to be discarded, and if +<function>XFilterEvent</function> +returns +<function>False</function>, +dispatch the event to the widget using +<xref linkend='XtDispatchEventToWidget' xrefstyle='select: title'/>. +The procedure should return +<function>True</function> +if either +<function>XFilterEvent</function> +or +<xref linkend='XtDispatchEventToWidget' xrefstyle='select: title'/> +returned +<function>True</function> +and +<function>False</function> +otherwise. +</para> + +<para> +If the event should not be dispatched to a widget, the event +dispatcher procedure should attempt to dispatch the event elsewhere as +appropriate and return +<function>True</function> +if it successfully dispatched the event and +<function>False</function> +otherwise. +</para> + +<para> +Some dispatchers for extension events may wish to forward events +according to the Intrinsics' keyboard focus mechanism. To determine +which widget is the end result of keyboard event forwarding, use +<xref linkend='XtGetKeyboardFocusWidget' xrefstyle='select: title'/>. +</para> + +<funcsynopsis id='XtGetKeyboardFocusWidget'> +<funcprototype> +<funcdef>Widget <function>XtGetKeyboardFocusWidget</function></funcdef> + <paramdef>Widget <parameter>widget</parameter></paramdef> +</funcprototype> +</funcsynopsis> + +<variablelist> + <varlistentry> + <term> + <emphasis remap='I'>widget</emphasis> + </term> + <listitem> + <para> +Specifies the widget to get forwarding information for. + </para> + </listitem> + </varlistentry> +</variablelist> + +<para> +The +<xref linkend='XtGetKeyboardFocusWidget' xrefstyle='select: title'/> +function returns the widget that would be the end result of keyboard +event forwarding for a keyboard event for the specified widget. +</para> + +<para> +To dispatch an event to a specified widget, use +<xref linkend='XtDispatchEventToWidget' xrefstyle='select: title'/>. +</para> + +<funcsynopsis id='XtDispatchEventToWidget'> +<funcprototype> +<funcdef>Boolean <function>XtDispatchEventToWidget</function></funcdef> + <paramdef>Widget <parameter>widget</parameter></paramdef> + <paramdef>XEvent *<parameter>event</parameter></paramdef> +</funcprototype> +</funcsynopsis> + +<variablelist> + <varlistentry> + <term> + <emphasis remap='I'>widget</emphasis> + </term> + <listitem> + <para> +Specifies the widget to which to dispatch the event. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <emphasis remap='I'>event</emphasis> + </term> + <listitem> + <para> +Specifies a pointer to the event to be dispatched. + </para> + </listitem> + </varlistentry> +</variablelist> + +<para> +The +<xref linkend='XtDispatchEventToWidget' xrefstyle='select: title'/> +function scans the list of registered event handlers for the +specified widget and calls each handler that has been registered +for the specified event type, subject to the <emphasis remap='I'>continue_to_dispatch</emphasis> +value returned by each handler. +The Intrinsics behave as if event handlers were registered at the head +of the list for +<function>Expose</function>, +<function>NoExpose</function>, +<function>GraphicsExpose</function>, +and +<function>VisibilityNotify</function> +events to invoke the widget's expose procedure according to the exposure +compression rules and to update the widget's <emphasis remap='I'>visible</emphasis> field +if <emphasis remap='I'>visible_interest</emphasis> is +<function>True</function>. +These internal event handlers never set <emphasis remap='I'>continue_to_dispatch</emphasis> to +<function>False</function>. +</para> + +<para> +<xref linkend='XtDispatchEventToWidget' xrefstyle='select: title'/> +returns +<function>True</function> +if any event handler was called and +<function>False</function> +otherwise. +</para> +</sect2> +</sect1> + +<sect1 id="Using_the_Intrinsics_in_a_Multi_Threaded_Environment"> +<title>Using the Intrinsics in a Multi-Threaded Environment</title> +<para> +The Intrinsics may be used in environments that offer multiple threads +of execution within the context of a single process. A multi-threaded +application using the Intrinsics must explicitly initialize the toolkit +for mutually exclusive access by calling +<xref linkend='XtToolkitThreadInitialize' xrefstyle='select: title'/>. +</para> +<sect2 id="Initializing_a_Multi_Threaded_Intrinsics_Application"> +<title>Initializing a Multi-Threaded Intrinsics Application</title> +<para> +To test and initialize Intrinsics support for mutually exclusive thread +access, call +<xref linkend='XtToolkitThreadInitialize' xrefstyle='select: title'/>. +</para> + +<funcsynopsis id='XtToolkitThreadInitialize'> +<funcprototype> +<funcdef>Boolean <function>XtToolkitThreadInitialize</function></funcdef> + <paramdef><parameter></parameter></paramdef> +</funcprototype> +</funcsynopsis> + +<para> +<xref linkend='XtToolkitThreadInitialize' xrefstyle='select: title'/> +returns <function>True</function> if the Intrinsics support mutually exclusive thread +access, otherwise it returns <function>False</function>. <xref linkend='XtToolkitThreadInitialize' xrefstyle='select: title'/> +must be called before +<xref linkend='XtCreateApplicationContext' xrefstyle='select: title'/>, +<xref linkend='XtAppInitialize' xrefstyle='select: title'/>, +<xref linkend='XtOpenApplication' xrefstyle='select: title'/>, +or +<function>XtSetLanguageProc</function> +is called. <xref linkend='XtToolkitThreadInitialize' xrefstyle='select: title'/> may be called more than once; +however, the application writer must ensure that it is not called +simultaneously by two or more threads. +</para> +</sect2> + +<sect2 id="Locking_tk_Data_Structures"> +<title>Locking X Toolkit Data Structures</title> +<para> +The Intrinsics employs two levels of locking: application context and +process. Locking an application context ensures mutually exclusive +access by a thread to the state associated with the application context, +including all displays and widgets associated with it. Locking a +process ensures mutually exclusive access by a thread to Intrinsics process +global data. +</para> + +<para> +A client may acquire a lock multiple times and the effect is cumulative. +The client must ensure that the lock is released an equal number of times in +order for the lock to be acquired by another thread. +</para> + +<para> +Most application writers will have little need to use locking as the +Intrinsics performs the necessary locking internally. +Resource converters are an exception. +They require the application context or process to be locked +before the application can safely call them directly, for example: +</para> +<literallayout > + ... + XtAppLock(app_context); + XtCvtStringToPixel(dpy, args, num_args, fromVal, toVal, closure_ret); + XtAppUnlock(app_context); + ... +</literallayout> +<para> +When the application relies upon +<xref linkend='XtConvertAndStore' xrefstyle='select: title'/> +or a converter to provide the storage for the results of a +conversion, the application should acquire the process lock before +calling out and hold the lock until the results have been copied. +</para> + +<para> +Application writers who write their own +utility functions, such as one which retrieves the being_destroyed field from +a widget instance, must lock the application context before accessing +widget internal data. For example: +</para> +<literallayout > +#include <X11/CoreP.h> +Boolean BeingDestroyed (widget) + Widget widget; +{ + Boolean ret; + XtAppLock(XtWidgetToApplicationContext(widget)); + ret = widget->core.being_destroyed; + XtAppUnlock(XtWidgetToApplicationContext(widget)); + return ret; +} +</literallayout> +<para> +A client that wishes to atomically call two or more Intrinsics functions +must lock the application context. For example: +</para> +<literallayout > + ... + XtAppLock(XtWidgetToApplicationContext(widget)); + XtUnmanageChild (widget1); + XtManageChild (widget2); + XtAppUnlock(XtWidgetToApplicationContext(widget)); + ... +</literallayout> +<sect3 id="Locking_the_Application_Context"> +<title>Locking the Application Context</title> +<para> +To ensure mutual exclusion of application context, display, or +widget internal state, use +<function>XtAppLock.</function> +</para> + +<funcsynopsis id='XtAppLock'> +<funcprototype> +<funcdef>void <function>XtAppLock</function></funcdef> + <paramdef>XtAppContext <parameter>app_context</parameter></paramdef> +</funcprototype> +</funcsynopsis> + +<variablelist> + <varlistentry> + <term> + <emphasis remap='I'>app_context</emphasis> + </term> + <listitem> + <para> +Specifies the application context to lock. + </para> + </listitem> + </varlistentry> +</variablelist> + +<para> +<xref linkend='XtAppLock' xrefstyle='select: title'/> blocks until it is able to acquire the lock. Locking the +application context also ensures that only the thread holding the lock +makes Xlib calls from within Xt. An application that makes its own +direct Xlib calls must either lock the application context around every +call or enable thread locking in Xlib. +</para> + +<para> +To unlock a locked application context, use +<function>XtAppUnlock.</function> +</para> + +<funcsynopsis id='XtAppUnlock'> +<funcprototype> +<funcdef>void <function>XtAppUnlock</function></funcdef> + <paramdef>XtAppContext <parameter>app_context</parameter></paramdef> +</funcprototype> +</funcsynopsis> + +<variablelist> + <varlistentry> + <term> + <emphasis remap='I'>app_context</emphasis> + </term> + <listitem> + <para> +Specifies the application context that was previously locked. + </para> + </listitem> + </varlistentry> +</variablelist> + + +</sect3> +<sect3 id="Locking_the_Process"> +<title>Locking the Process</title> +<para> +To ensure mutual exclusion of X Toolkit process global data, a +widget writer must use +<function>XtProcessLock.</function> +</para> + +<funcsynopsis id='XtProcessLock'> +<funcprototype> +<funcdef>void <function>XtProcessLock</function></funcdef> + <paramdef><parameter></parameter></paramdef> +</funcprototype> +</funcsynopsis> + +<para> +<xref linkend='XtProcessLock' xrefstyle='select: title'/> blocks until it is able to acquire the lock. +Widget writers may use XtProcessLock to guarantee mutually exclusive +access to widget static data. +</para> + +<para> +To unlock a locked process, use +<xref linkend='XtProcessUnlock' xrefstyle='select: title'/>. +</para> + +<funcsynopsis id='XtProcessUnlock'> +<funcprototype> +<funcdef>void <function>XtProcessUnlock</function></funcdef> + <paramdef><parameter></parameter></paramdef> +</funcprototype> +</funcsynopsis> + +<para> +To lock both an application context and the process at the same +time, call +<xref linkend='XtAppLock' xrefstyle='select: title'/> +first and then +<xref linkend='XtProcessLock' xrefstyle='select: title'/>. +To release both locks, call +<xref linkend='XtProcessUnlock' xrefstyle='select: title'/> +first and then +<xref linkend='XtAppUnlock' xrefstyle='select: title'/>. +The order is important to avoid deadlock. +</para> +</sect3> +</sect2> + +<sect2 id="Event_Management_in_a_Multi_Threaded_Environment"> +<title>Event Management in a Multi-Threaded Environment</title> +<para> +In a nonthreaded environment an application writer could reasonably +assume that it is safe to exit the application from a quit callback. +This assumption may no longer hold true in a multi-threaded environment; +therefore it is desirable to provide a mechanism to terminate an +event-processing loop without necessarily terminating its thread. +</para> + +<para> +To indicate that the event loop should terminate after the current +event dispatch has completed, use +<xref linkend='XtAppSetExitFlag' xrefstyle='select: title'/>. +</para> + +<funcsynopsis id='XtAppSetExitFlag'> +<funcprototype> +<funcdef>void <function>XtAppSetExitFlag</function></funcdef> + <paramdef>XtAppContext <parameter>app_context</parameter></paramdef> +</funcprototype> +</funcsynopsis> + +<variablelist> + <varlistentry> + <term> + <emphasis remap='I'>app_context</emphasis> + </term> + <listitem> + <para> +Specifies the application context. + </para> + </listitem> + </varlistentry> +</variablelist> + +<para> +<xref linkend='XtAppMainLoop' xrefstyle='select: title'/> +tests the value of the flag and will return if the flag is <function>True</function>. +</para> + +<para> +Application writers who implement their own main loop may test the +value of the exit flag with +<xref linkend='XtAppGetExitFlag' xrefstyle='select: title'/>. +</para> + +<funcsynopsis id='XtAppGetExitFlag'> +<funcprototype> +<funcdef>Boolean <function>XtAppGetExitFlag</function></funcdef> + <paramdef>XtAppContext <parameter>app_context</parameter></paramdef> +</funcprototype> +</funcsynopsis> + +<variablelist> + <varlistentry> + <term> + <emphasis remap='I'>app_context</emphasis> + </term> + <listitem> + <para> +Specifies the application context. + </para> + </listitem> + </varlistentry> +</variablelist> + +<para> +<xref linkend='XtAppGetExitFlag' xrefstyle='select: title'/> +will normally return <function>False</function>, indicating that event processing +may continue. When +<xref linkend='XtAppGetExitFlag' xrefstyle='select: title'/> +returns <function>True</function>, the loop must terminate and return to the caller, +which might then destroy the application context. +</para> + +<para> +Application writers should be aware that, if a thread is blocked in +<xref linkend='XtAppNextEvent' xrefstyle='select: title'/>, +<xref linkend='XtAppPeekEvent' xrefstyle='select: title'/>, +or +<xref linkend='XtAppProcessEvent' xrefstyle='select: title'/> +and another thread in the same application context opens a new display, +adds an alternate input, or a timeout, any new source(s) will not +normally be "noticed" by the blocked thread. Any new sources are +"noticed" the next time one of these functions is called. +</para> + +<para> +The Intrinsics manage access to events on a last-in, first-out basis. If +multiple threads in the same application context block in +<xref linkend='XtAppNextEvent' xrefstyle='select: title'/>, +<xref linkend='XtAppPeekEvent' xrefstyle='select: title'/>, +or +<xref linkend='XtAppProcessEvent' xrefstyle='select: title'/>, +the last thread to call one of these functions is the first +thread to return. +</para> +</sect2> +</sect1> +</chapter> |