Support _NET_FRAME_EXTENTS.

This patch adds support for the _NET_FRAME_EXTENTS property as
described in the EWMH spec.  With it I was able to use the compton
compositing manager to draw fully opaque windows with semi-transparent
titlebars and resizebars.

Set the _NET_FRAME_EXTENTS property based on border widths and
titlebar/resizebar heights.

The EWMH spec says:

"_NET_FRAME_EXTENTS, left, right, top, bottom, CARDINAL[4]/32

The Window Manager MUST set _NET_FRAME_EXTENTS to the extents of the
window's frame.  left, right, top and bottom are widths of the
respective borders added by the Window Manager."

src/window.c

@@ -2039,6 +2039,9 @@ void wWindowConfigure(WWindow *wwin, int req_x, int req_y, int req_width, int re
 
 	if (synth_notify)
 		wWindowSynthConfigureNotify(wwin);
+
+	wNETFrameExtents(wwin);
+
 	XFlush(dpy);
 }
 

src/wmspec.c

@@ -120,6 +120,8 @@ static Atom net_wm_icon;
 static Atom net_wm_pid;		/* TODO */
 static Atom net_wm_handled_icons;	/* FIXME: see net_wm_icon_geometry */
 
+static Atom net_frame_extents;
+
 /* Window Manager Protocols */
 static Atom net_wm_ping;	/* TODO */
 
@@ -193,6 +195,8 @@ static atomitem_t atomNames[] = {
 	{"_NET_WM_PID", &net_wm_pid},
 	{"_NET_WM_HANDLED_ICONS", &net_wm_handled_icons},
 
+	{"_NET_FRAME_EXTENTS", &net_frame_extents},
+
 	{"_NET_WM_PING", &net_wm_ping},
 
 	{"UTF8_STRING", &utf8_string},
@@ -294,6 +298,8 @@ static void setSupportedHints(WScreen * scr)
 	atom[i++] = net_wm_icon;
 	atom[i++] = net_wm_handled_icons;
 
+	atom[i++] = net_frame_extents;
+
 	atom[i++] = net_wm_name;
 	atom[i++] = net_wm_icon_name;
 
@@ -1605,3 +1611,26 @@ static void wsobserver(void *self, WMNotification * notif)
 		updateWorkspaceNames(scr);
 	}
 }
+
+void wNETFrameExtents(WWindow *wwin)
+{
+	long extents[4] = { 0, 0, 0, 0 };
+
+	/* The extents array describes dimensions which are not
+	 * part of the client window.  In our case that means
+	 * widths of the border and heights of the titlebar and resizebar.
+	 *
+	 * Index 0 = left
+	 *       1 = right
+	 *       2 = top
+	 *       3 = bottom
+	 */
+	if (!wwin->client_flags.no_border)
+		extents[0] = extents[1] = FRAME_BORDER_WIDTH;
+	if (wwin->frame->titlebar)
+		extents[2] = wwin->frame->titlebar->height;
+	if (wwin->frame->resizebar)
+		extents[3] = wwin->frame->resizebar->height;
+
+	XChangeProperty(dpy, wwin->client_win, net_frame_extents, XA_CARDINAL, 32, PropModeReplace, (unsigned char *) extents, 4);
+}

src/wmspec.h

@@ -44,4 +44,5 @@ int wNETWMGetPidForWindow(Window window);
 int wNETWMGetCurrentDesktopFromHint(WScreen *scr);
 char *wNETWMGetIconName(Window window);
 char *wNETWMGetWindowName(Window window);
+void wNETFrameExtents(WWindow *wwin);
 #endif