Select correct client window in WM’s using virtual roots

From bug 2185¹

When manually selecting a window, xprop finds the top-level window containing
the pointer and uses XmuClientWindow to attempt to find a client window having
WM_STATE set.

In a WM using virtual roots (e.g. enlightenment, desks other than first) this
fails beacuse the top-level window is a virtual root, and XmuClientWindow seems
to find the first client having WM_STATE set, which only by coincidence will be
the one the user intended to select (i.e. containing the pointer).

The solution is to descend the window hierarchy at the pointer location to find
a window with WM_STATE set.

1] https://bugs.freedesktop.org/show_bug.cgi?id=2185

Signed-off-by: James Cloos <cloos@jhcloos.com>

7 files changed, 256 insertions, 17 deletions

diff --git a/Makefile.am b/Makefile.am
index e4fc5ad..d3fc24a 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -27,6 +27,8 @@ xprop_LDADD = $(XPROP_LIBS)
 xprop_SOURCES =	\
         dsimple.c \
         dsimple.h \
+        clientwin.c \
+        clientwin.h \
         xprop.c
 
 appman_PRE = \
diff --git a/clientwin.c b/clientwin.c
new file mode 100644
index 0000000..808adec
--- /dev/null
+++ b/clientwin.c
@@ -0,0 +1,214 @@
+/*
+ * Copyright 2007 Kim woelders
+ *
+ * Permission to use, copy, modify, distribute, and sell this software and its
+ * documentation for any purpose is hereby granted without fee, provided that
+ * the above copyright notice appear in all copies and that both that copyright
+ * notice and this permission notice appear in supporting documentation, and
+ * that the name of the copyright holders not be used in advertising or
+ * publicity pertaining to distribution of the software without specific,
+ * written prior permission.  The copyright holders make no representations
+ * about the suitability of this software for any purpose.  It is provided "as
+ * is" without express or implied warranty.
+ *
+ * THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
+ * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
+ * EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY SPECIAL, INDIRECT OR
+ * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
+ * DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
+ * TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
+ * OF THIS SOFTWARE.
+ */
+#include <X11/Xatom.h>
+#include <X11/Xlib.h>
+
+static Atom atom_wm_state = None;
+
+/*
+ * Check if window has given property
+ */
+static Bool
+Window_Has_Property(Display * dpy, Window win, Atom atom)
+{
+    Atom type_ret;
+    int format_ret;
+    unsigned char *prop_ret;
+    unsigned long bytes_after, num_ret;
+
+    type_ret = None;
+    prop_ret = NULL;
+    XGetWindowProperty(dpy, win, atom, 0, 0, False, AnyPropertyType,
+                       &type_ret, &format_ret, &num_ret,
+                       &bytes_after, &prop_ret);
+    if (prop_ret)
+        XFree(prop_ret);
+
+    return (type_ret != None) ? True : False;
+}
+
+/*
+ * Check if window is viewable
+ */
+static Bool
+Window_Is_Viewable(Display * dpy, Window win)
+{
+    Bool ok;
+    XWindowAttributes xwa;
+
+    XGetWindowAttributes(dpy, win, &xwa);
+
+    ok = (xwa.class == InputOutput) && (xwa.map_state == IsViewable);
+
+    return ok;
+}
+
+/*
+ * Find a window that has WM_STATE set in the window tree below win.
+ * Unmapped/unviewable windows are not considered valid matches.
+ * Children are searched in top-down stacking order.
+ * The first matching window is returned, None if no match is found.
+ */
+Window
+Find_Client_In_Children(Display * dpy, Window win)
+{
+    Window root, parent;
+    Window *children;
+    unsigned int n_children;
+    int i;
+
+    if (!XQueryTree(dpy, win, &root, &parent, &children, &n_children))
+        return None;
+    if (!children)
+        return None;
+
+    /* Check each child for WM_STATE and other validity */
+    win = None;
+    for (i = (int) n_children - 1; i >= 0; i--) {
+        if (!Window_Is_Viewable(dpy, children[i])) {
+            children[i] = None; /* Don't bother descending into this one */
+            continue;
+        }
+        if (!Window_Has_Property(dpy, children[i], atom_wm_state))
+            continue;
+
+        /* Got one */
+        win = children[i];
+        goto done;
+    }
+
+    /* No children matched, now descend into each child */
+    for (i = (int) n_children - 1; i >= 0; i--) {
+        if (children[i] == None)
+            continue;
+        win = Find_Client_In_Children(dpy, children[i]);
+        if (win != None)
+            break;
+    }
+
+  done:
+    XFree(children);
+
+    return win;
+}
+
+/*
+ * Find virtual roots (_NET_VIRTUAL_ROOTS)
+ */
+unsigned long *
+Find_Roots(Display * dpy, Window root, unsigned int *num)
+{
+    Atom type_ret;
+    int format_ret;
+    unsigned char *prop_ret;
+    unsigned long bytes_after, num_ret;
+    Atom atom;
+
+    *num = 0;
+    atom = XInternAtom(dpy, "_NET_VIRTUAL_ROOTS", False);
+    if (!atom)
+        return NULL;
+
+    type_ret = None;
+    prop_ret = NULL;
+    if (XGetWindowProperty(dpy, root, atom, 0, 0x7fffffff, False,
+                           XA_WINDOW, &type_ret, &format_ret, &num_ret,
+                           &bytes_after, &prop_ret) != Success)
+        return NULL;
+
+    if (prop_ret && type_ret == XA_WINDOW && format_ret == 32) {
+        *num = num_ret;
+        return ((unsigned long *) prop_ret);
+    }
+    if (prop_ret)
+        XFree(prop_ret);
+
+    return NULL;
+}
+
+/*
+ * Find child window at pointer location
+ */
+static Window
+Find_Child_At_Pointer(Display * dpy, Window win)
+{
+    Window root_return, child_return;
+    int dummyi;
+    unsigned int dummyu;
+
+    XQueryPointer(dpy, win, &root_return, &child_return,
+                  &dummyi, &dummyi, &dummyi, &dummyi, &dummyu);
+
+    return child_return;
+}
+
+/*
+ * Find client window at pointer location
+ *
+ * root   is the root window.
+ * subwin is the subwindow reported by a ButtonPress event on root.
+ *
+ * If the WM uses virtual roots subwin may be a virtual root.
+ * If so, we descend the window stack at the pointer location and assume the
+ * child is the client or one of its WM frame windows.
+ * This will of course work only if the virtual roots are children of the real
+ * root.
+ */
+Window
+Find_Client(Display * dpy, Window root, Window subwin)
+{
+    unsigned long *roots;
+    unsigned int i, n_roots;
+    Window win;
+
+    /* Check if subwin is a virtual root */
+    roots = Find_Roots(dpy, root, &n_roots);
+    for (i = 0; i < n_roots; i++) {
+        if (subwin != roots[i])
+            continue;
+        win = Find_Child_At_Pointer(dpy, subwin);
+        if (win == None)
+            return subwin;      /* No child - Return virtual root. */
+        subwin = win;
+        break;
+    }
+    if (roots)
+        XFree(roots);
+
+    if (atom_wm_state == None) {
+        atom_wm_state = XInternAtom(dpy, "WM_STATE", False);
+        if (!atom_wm_state)
+            return subwin;
+    }
+
+    /* Check if subwin has WM_STATE */
+    if (Window_Has_Property(dpy, subwin, atom_wm_state))
+        return subwin;
+
+    /* Attempt to find a client window in subwin's children */
+    win = Find_Client_In_Children(dpy, subwin);
+    if (win != None)
+        return win;             /* Found a client */
+
+    /* Did not find a client */
+    return subwin;
+}
diff --git a/clientwin.h b/clientwin.h
new file mode 100644
index 0000000..9fc59b5
--- /dev/null
+++ b/clientwin.h
@@ -0,0 +1,29 @@
+/*
+ * Copyright 2007 Kim woelders
+ *
+ * Permission to use, copy, modify, distribute, and sell this software and its
+ * documentation for any purpose is hereby granted without fee, provided that
+ * the above copyright notice appear in all copies and that both that copyright
+ * notice and this permission notice appear in supporting documentation, and
+ * that the name of the copyright holders not be used in advertising or
+ * publicity pertaining to distribution of the software without specific,
+ * written prior permission.  The copyright holders make no representations
+ * about the suitability of this software for any purpose.  It is provided "as
+ * is" without express or implied warranty.
+ *
+ * THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
+ * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
+ * EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY SPECIAL, INDIRECT OR
+ * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
+ * DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
+ * TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
+ * OF THIS SOFTWARE.
+ */
+#ifndef _CLIENTWIN_H_
+#define _CLIENTWIN_H_
+
+#include <X11/Xlib.h>
+
+extern Window Find_Client(Display * dpy, Window root, Window target_win);
+
+#endif
diff --git a/configure.ac b/configure.ac
index da8ebb8..78e4049 100644
--- a/configure.ac
+++ b/configure.ac
@@ -38,7 +38,7 @@ AC_PROG_INSTALL
 AC_CHECK_HEADERS_ONCE([wchar.h wctype.h])
 
 # Checks for pkg-config packages
-PKG_CHECK_MODULES(XPROP, xmuu x11)
+PKG_CHECK_MODULES(XPROP, x11)
 AC_SUBST(XPROP_CFLAGS)
 AC_SUBST(XPROP_LIBS)
 
diff --git a/dsimple.c b/dsimple.c
index 0c9fce8..2642e31 100644
--- a/dsimple.c
+++ b/dsimple.c
@@ -41,6 +41,7 @@ from The Open Group.
  * Written by Mark Lillibridge.   Last updated 7/1/87
  */
 
+#include "clientwin.h"
 #include "dsimple.h"
 
 /*
@@ -263,7 +264,7 @@ Window Select_Window_Args(
  * Routine to let user select a window using the mouse
  */
 
-Window Select_Window(Display *dpy)
+Window Select_Window(Display *dpy, int descend)
 {
   int status;
   Cursor cursor;
@@ -302,6 +303,11 @@ Window Select_Window(Display *dpy)
 
   XUngrabPointer(dpy, CurrentTime);      /* Done with pointer */
 
+  if (!descend || (target_win == root))
+    return(target_win);
+
+  target_win = Find_Client(dpy, root, target_win);
+
   return(target_win);
 }
 
diff --git a/dsimple.h b/dsimple.h
index 7b53c3c..7557571 100644
--- a/dsimple.h
+++ b/dsimple.h
@@ -78,7 +78,7 @@ void usage(void);
  * Send bugs, etc. to chariot@athena.mit.edu.
  */
 
-Window Select_Window(Display *);
+Window Select_Window(Display *, int descend);
 Window Window_With_Name(Display *, Window, const char *);
 #ifdef __GNUC__
 void Fatal_Error(char *, ...) __attribute__((__noreturn__));
diff --git a/xprop.c b/xprop.c
index c489486..f1bf02a 100644
--- a/xprop.c
+++ b/xprop.c
@@ -51,7 +51,6 @@ from The Open Group.
 #endif
 
 #include <X11/Xatom.h>
-#include <X11/Xmu/WinUtil.h>
 
 #include "dsimple.h"
 
@@ -1702,19 +1701,8 @@ main (int argc, char **argv)
     if ((remove_props != NULL || set_props != NULL) && argc > 0)
 	usage();
 
-    if (target_win == None) {
-	target_win = Select_Window(dpy);
-	if (target_win != None && !frame_only) {
-	    Window root;
-	    int dummyi;
-	    unsigned int dummy;
-
-	    if (XGetGeometry (dpy, target_win, &root, &dummyi, &dummyi,
-			      &dummy, &dummy, &dummy, &dummy)
-		&& target_win != root)
-		target_win = XmuClientWindow (dpy, target_win);
-	}
-    }
+    if (target_win == None)
+	target_win = Select_Window(dpy, !frame_only);
 
     if (remove_props != NULL) {
 	int count;