diff options
Diffstat (limited to 'specs/ch08.xml')
| -rw-r--r-- | specs/ch08.xml | 157 |
1 files changed, 157 insertions, 0 deletions
diff --git a/specs/ch08.xml b/specs/ch08.xml new file mode 100644 index 0000000..08524a8 --- /dev/null +++ b/specs/ch08.xml @@ -0,0 +1,157 @@ +<chapter id='Symbolic_Names'> +<title>Symbolic Names</title> + +<para> +The core protocol does not provide any information to clients other than that +actually used to interpret events. This makes it difficult to write a client +which presents the keyboard to a user in an easy-to-understand way. Such +applications have to examine the vendor string and keycodes to determine the +type of keyboard connected to the server and have to examine keysyms and +modifier mappings to determine the effects of most modifiers (the <emphasis> +Shift</emphasis> +, <emphasis> +Lock</emphasis> + and <emphasis> +Control</emphasis> + modifiers are defined by the core protocol but no semantics are implied for +any other modifiers). +</para> + + +<para> +This extension provides such applications with symbolic names for most +components of the keyboard extension and a description of the physical layout +of the keyboard. +</para> + + +<para> +The <emphasis> +keycodes</emphasis> + name describes the range and meaning of the keycodes returned by the keyboard +in question; the <emphasis> +keyboard</emphasis> + <emphasis> +geometry </emphasis> +name describes the physical location, size and shape of the various keys on the +keyboard. As an example to distinguish between these two names, consider +function keys on PC-compatible keyboards. Function keys are sometimes above the +main keyboard and sometimes to the left of the main keyboard, but the same +keycode is used for the key that is logically <emphasis> +F1</emphasis> + regardless of physical position. Thus, all PC-compatible keyboards might share +a keycodes name but different geometry names. +</para> + +<note><para>The keycodes name is intended to be a very general description of +the keycodes returned by a keyboard; A single keycodes name might cover +keyboards with differing numbers of keys provided that the keys that all keys +have the same semantics when present. For example, 101 and 102 key PC keyboards +might use the same name. Applications can use the keyboard geometry to +determine which subset of the named keyboard type is in use.</para></note> + +<para> +The <emphasis> +symbols</emphasis> + name identifies the symbols bound to the keys. The symbols name is a human or +application-readable description of the intended locale or usage of the +keyboard with these symbols. The <emphasis> +physical symbols</emphasis> + name describes the symbols actually engraved on the keyboard, which might be +different than the symbols currently being used. +</para> + + +<para> +The <emphasis> +types</emphasis> + name provides some information about the set of key types that can be +associated with the keyboard keys. The <emphasis> +compat</emphasis> + name provides some information about the rules used to bind actions to keys +changed using core protocol requests. +</para> + + +<para> +The <emphasis> +compat</emphasis> +, <emphasis> +types</emphasis> +, <emphasis> +keycodes</emphasis> +, <emphasis> +symbols</emphasis> + and <emphasis> +geometry</emphasis> + names typically correspond to the keyboard components from which the current +keyboard description was assembled. These components are stored individually in +the server’s database of keyboard components, described in +<link linkend='The_Server_Database_of_Keyboard_Components'> +The Server Database of Keyboard +Components</link>, and can be combined to assemble a complete keyboard +description. +</para> + + +<para> +Each key has a four-byte symbolic name. The key name links keys with similar +functions or in similar positions on keyboards that report different scan +codes. <emphasis> +Key aliases</emphasis> + allow the keyboard layout designer to assign multiple names to a single key, +to make it easier to refer to keys using either their position <emphasis> +or</emphasis> + their "function." +</para> + + +<para> +For example, consider the common keyboard customizations: +</para> + +<itemizedlist> +<listitem> + <para>Set the "key to the left of the letter a" to be a control key. + </para> +</listitem> +<listitem> + <para>Change the "caps lock" key, wherever it might be, to a control key. + </para> +</listitem> +</itemizedlist> + +<para> +If we specify key names by position, the first customization is simple but the +second is impossible; if we specify key names by function, the second +customization is simple but the first is impossible. Using key aliases, we can +specify both function and position for "troublesome" keys, and both +customizations are straightforward. +</para> + + +<para> +Key aliases can be specified both in the symbolic names component and in the +keyboard geometry (see <link linkend='Keyboard_Geometry'>Keyboard +Geometry</link>). Both sets of aliases are always valid, but key alias +definitions in the keyboard geometry have priority; if both symbolic names and +geometry include aliases, applications should consider the definitions from the +geometry before considering the definitions from the symbolic names section. +</para> + + +<para> +XKB provides symbolic names for each of the four keyboard groups, sixteen +virtual modifiers, thirty-two keyboard indicators, and up to <emphasis> +MaxRadioGroups</emphasis> + (32) radio groups. +</para> + + +<para> +XKB allows keyboard layout designers or editors to assign names to each key +type and to each of the levels in a key type. For example, the second position +on an alphabetic key might be called the "Caps" level while the second position +on a numeric keypad key might be called the "Num Lock" level. +</para> +</chapter> |