Add support for _NET_WM_FULLSCREEN_MONITORS

This patch adds the _NET_WM_FULLSCREEN_MONITORS hint as defined in EWMH which is based on Xinerama.
It's allowing a window to be displayed fullscreen on multiple monitors.

Issue mentioned at #8
Specs at https://specifications.freedesktop.org/wm-spec/1.5/ar01s06.html#idm45763309187776
GTK test program used https://bugzilla.gnome.org/show_bug.cgi?id=414476

src/actions.c

@@ -912,6 +912,54 @@ void wUnmaximizeWindow(WWindow *wwin)
 	WMPostNotificationName(WMNChangedState, wwin, "maximize");
 }
 
+#ifdef USE_XINERAMA
+void wFullscreenMonitorsWindow(WWindow *wwin, unsigned long top, unsigned long bottom,
+					unsigned long left, unsigned long right)
+{
+	int i;
+	long monitor;
+	WMRect rect1, rect2;
+
+	if ((int)top < wwin->screen_ptr->xine_info.count &&
+	    (int)bottom < wwin->screen_ptr->xine_info.count &&
+	    (int)left < wwin->screen_ptr->xine_info.count &&
+	    (int)right < wwin->screen_ptr->xine_info.count) {
+		wwin->flags.fullscreen_monitors[0] = top;
+		wwin->flags.fullscreen_monitors[1] = bottom;
+		wwin->flags.fullscreen_monitors[2] = left;
+		wwin->flags.fullscreen_monitors[3] = right;
+	} else {
+		wwin->flags.fullscreen_monitors[0] = -1;
+		return;
+	}
+
+	wwin->flags.fullscreen = True;
+	wWindowConfigureBorders(wwin);
+	ChangeStackingLevel(wwin->frame->core, WMFullscreenLevel);
+
+	wwin->bfs_geometry.x = wwin->frame_x;
+	wwin->bfs_geometry.y = wwin->frame_y;
+	wwin->bfs_geometry.width = wwin->frame->core->width;
+	wwin->bfs_geometry.height = wwin->frame->core->height;
+
+	i = 0;
+	monitor = wwin->flags.fullscreen_monitors[i];
+	rect1 = wwin->screen_ptr->xine_info.screens[monitor];
+
+	for (i = 1; i <= 3; i++) {
+		monitor = wwin->flags.fullscreen_monitors[i];
+		rect2 = wwin->screen_ptr->xine_info.screens[monitor];
+		wGetRectUnion(&rect1, &rect2, &rect1);
+	}
+	wWindowConfigure(wwin, rect1.pos.x, rect1.pos.y, rect1.size.width, rect1.size.height);
+
+	wwin->screen_ptr->bfs_focused_window = wwin->screen_ptr->focused_window;
+	wSetFocusTo(wwin->screen_ptr, wwin);
+
+	WMPostNotificationName(WMNChangedState, wwin, "fullscreen");
+}
+#endif
+
 void wFullscreenWindow(WWindow *wwin)
 {
 	int head;

src/actions.h

@@ -75,6 +75,9 @@ void wArrangeIcons(WScreen *scr, Bool arrangeAll);
 
 void wMakeWindowVisible(WWindow *wwin);
 
+void wFullscreenMonitorsWindow(WWindow *wwin, unsigned long top, unsigned long bottom,
+					unsigned long left, unsigned long right);
+
 void wFullscreenWindow(WWindow *wwin);
 void wUnfullscreenWindow(WWindow *wwin);
 

src/window.c

@@ -688,6 +688,9 @@ WWindow *wManageWindow(WScreen *scr, Window window)
 	XChangeWindowAttributes(dpy, window, CWEventMask | CWDontPropagate | CWSaveUnder, &attribs);
 	XSetWindowBorderWidth(dpy, window, 0);
 
+	if (wwin->wm_class != NULL && strcmp(wwin->wm_class, "DockApp") != 0)
+		wwin->flags.fullscreen_monitors[0] = -1;
+
 	/* get hints from GNUstep app */
 	if (wwin->wm_class != NULL && strcmp(wwin->wm_class, "GNUstep") == 0)
 		wwin->flags.is_gnustep = 1;

src/window.h

@@ -254,6 +254,7 @@ typedef struct WWindow {
 		unsigned int maximized:7;
 		unsigned int old_maximized:7;
 		unsigned int fullscreen:1;
+		long fullscreen_monitors[4];
 		unsigned int omnipresent:1;
 		unsigned int semi_focused:1;
 		/* window type flags */

src/wmspec.c

@@ -77,6 +77,9 @@ static Atom net_wm_visible_name;	/* TODO (unnecessary?) */
 static Atom net_wm_icon_name;
 static Atom net_wm_visible_icon_name;	/* TODO (unnecessary?) */
 static Atom net_wm_desktop;
+#ifdef USE_XINERAMA
+static Atom net_wm_fullscreen_monitors;
+#endif
 static Atom net_wm_window_type;
 static Atom net_wm_window_type_desktop;
 static Atom net_wm_window_type_dock;
@@ -161,6 +164,9 @@ static atomitem_t atomNames[] = {
 	{"_NET_WM_ICON_NAME", &net_wm_icon_name},
 	{"_NET_WM_VISIBLE_ICON_NAME", &net_wm_visible_icon_name},
 	{"_NET_WM_DESKTOP", &net_wm_desktop},
+#ifdef USE_XINERAMA
+	{"_NET_WM_FULLSCREEN_MONITORS", &net_wm_fullscreen_monitors},
+#endif
 	{"_NET_WM_WINDOW_TYPE", &net_wm_window_type},
 	{"_NET_WM_WINDOW_TYPE_DESKTOP", &net_wm_window_type_desktop},
 	{"_NET_WM_WINDOW_TYPE_DOCK", &net_wm_window_type_dock},
@@ -287,6 +293,9 @@ static void setSupportedHints(WScreen *scr)
 	atom[i++] = net_wm_moveresize;
 #endif
 	atom[i++] = net_wm_desktop;
+#ifdef USE_XINERAMA
+	atom[i++] = net_wm_fullscreen_monitors;
+#endif
 	atom[i++] = net_wm_window_type;
 	atom[i++] = net_wm_window_type_desktop;
 	atom[i++] = net_wm_window_type_dock;
@@ -1027,6 +1036,9 @@ static void updateStateHint(WWindow *wwin, Bool changedWorkspace, Bool del)
 {				/* changeable */
 	if (del) {
 		XDeleteProperty(dpy, wwin->client_win, net_wm_state);
+#ifdef USE_XINERAMA
+		XDeleteProperty(dpy, wwin->client_win, net_wm_fullscreen_monitors);
+#endif
 	} else {
 		Atom state[15];	/* nr of defined state atoms */
 		int i = 0;
@@ -1067,6 +1079,20 @@ static void updateStateHint(WWindow *wwin, Bool changedWorkspace, Bool del)
 
 		XChangeProperty(dpy, wwin->client_win, net_wm_state, XA_ATOM, 32,
 				PropModeReplace, (unsigned char *)state, i);
+
+#ifdef USE_XINERAMA
+		if (wwin->flags.fullscreen && (wwin->flags.fullscreen_monitors[0] != -1)) {
+			unsigned long data[4];
+
+			data[0] = wwin->flags.fullscreen_monitors[0];
+			data[1] = wwin->flags.fullscreen_monitors[1];
+			data[2] = wwin->flags.fullscreen_monitors[2];
+			data[3] = wwin->flags.fullscreen_monitors[3];
+
+			XChangeProperty(dpy, wwin->client_win, net_wm_fullscreen_monitors, XA_CARDINAL, 32,
+				PropModeReplace, (unsigned char *)data, 4);
+		}
+#endif
 	}
 }
 
@@ -1260,8 +1286,10 @@ static void doStateAtom(WWindow *wwin, Atom state, int set, Bool init)
 		} else {
 			if (set)
 				wFullscreenWindow(wwin);
-			else
+			else {
 				wUnfullscreenWindow(wwin);
+				wwin->flags.fullscreen_monitors[0] = -1;
+			}
 		}
 	} else if (state == net_wm_state_above) {
 		if (set == _NET_WM_STATE_TOGGLE)
@@ -1759,8 +1787,30 @@ Bool wNETWMProcessClientMessage(XClientMessageEvent *event)
 			wWindowChangeWorkspace(wwin, desktop);
 		}
 		return True;
+
+#ifdef USE_XINERAMA
+	} else if (event->message_type == net_wm_fullscreen_monitors) {
+		unsigned long top, bottom, left, right, src_indication;
+
+		top = event->data.l[0];
+		bottom = event->data.l[1];
+		left = event->data.l[2];
+		right = event->data.l[3];
+		src_indication = event->data.l[4];
+
+		if (src_indication > 1)
+			wwarning("_NET_WM_FULLSCREEN_MONITORS source indication %ld not supported", src_indication);
+
+		wFullscreenMonitorsWindow(wwin, top, bottom, left, right);
+		return True;
 	}
+#else
+	}
+#endif
 
+#ifdef DEBUG_WMSPEC
+	wmessage("processClientMessage unsupported type %s", XGetAtomName(dpy, event->message_type));
+#endif
 	return False;
 }
 

src/xinerama.c

@@ -410,3 +410,33 @@ WMPoint wGetPointToCenterRectInHead(WScreen * scr, int head, int width, int heig
 
 	return p;
 }
+
+/* Find the bounding rect of the union of two rectangles */
+void wGetRectUnion(const WMRect *rect1, const WMRect *rect2, WMRect *dest)
+{
+	int dest_x, dest_y;
+	int dest_w, dest_h;
+
+	dest_x = rect1->pos.x;
+	dest_y = rect1->pos.y;
+	dest_w = rect1->size.width;
+	dest_h = rect1->size.height;
+
+	if (rect2->pos.x < dest_x) {
+		dest_w += dest_x - rect2->pos.x;
+		dest_x = rect2->pos.x;
+	}
+	if (rect2->pos.y < dest_y) {
+		dest_h += dest_y - rect2->pos.y;
+		dest_y = rect2->pos.y;
+	}
+	if (rect2->pos.x + rect2->size.width > dest_x + dest_w)
+		dest_w = rect2->pos.x + rect2->size.width - dest_x;
+	if (rect2->pos.y + rect2->size.height > dest_y + dest_h)
+		dest_h = rect2->pos.y + rect2->size.height - dest_y;
+
+	dest->pos.x = dest_x;
+	dest->pos.y = dest_y;
+	dest->size.width = dest_w;
+	dest->size.height = dest_h;
+}

src/xinerama.h

@@ -60,6 +60,8 @@ WArea wGetUsableAreaForHead(WScreen *scr, int head, WArea *totalAreaPtr, Bool no
 
 WMPoint wGetPointToCenterRectInHead(WScreen *scr, int head, int width, int height);
 
+void wGetRectUnion(const WMRect *rect1, const WMRect *rect2, WMRect *dest);
+
 Bool wWindowTouchesHead(WWindow *wwin, int head);
 Bool wAppIconTouchesHead(WAppIcon *aicon, int head);