xwm: detect legacy fullscreen on MapRequest

The legacy fullscreen state needs to be detected at MapRequest time,
because that is when the X11 client has alredy set up the initial window
state.

Doing it at xserver_map_shell_surface() meant that it would be done as a
response to Xwayland creating the wl_surface and XWM receiving the
WL_SURFACE_ID ClientMessage, whichever came later. At that point the X11
client might still be setting things up in theory, though in practice
most of the X11 communication has already happened when
xserver_map_shell_surface() gets called.

The real reason for this is to clean up xserver_map_shell_surface() from
everything that would affect drawing the decorations. This patch is one
part of that clean-up.

The weston_output_weak_ref logic is not put into compositor.h, because
there are no other users for it at this time. We need to protect against
the output going away.

A side-effect of this patch is that saved_width and saved_height will
now get overwritten also for legacy fullscreen windows. Previously, they
were left to zero as far as I could tell.

NOTE: This stops override-redirect legacy fullscreen windows from being
detected as fullscreen. MapRequest processing does not happen for OR
windows. These windows get detected as type XWAYLAND instead.

Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
Reviewed-by: Quentin Glidic <sardemff7+git@sardemff7.net>

xwayland/window-manager.c

@@ -35,6 +35,7 @@
 #include <errno.h>
 #include <unistd.h>
 #include <signal.h>
+#include <assert.h>
 #include <X11/Xcursor/Xcursor.h>
 #include <linux/input.h>
 
@@ -125,6 +126,11 @@ struct motif_wm_hints {
 #define _NET_WM_MOVERESIZE_MOVE_KEYBOARD    10   /* move via keyboard */
 #define _NET_WM_MOVERESIZE_CANCEL           11   /* cancel operation */
 
+struct weston_output_weak_ref {
+	struct weston_output *output;
+	struct wl_listener destroy_listener;
+};
+
 struct weston_wm_window {
 	struct weston_wm *wm;
 	xcb_window_t id;
@@ -148,6 +154,7 @@ struct weston_wm_window {
 	int width, height;
 	int x, y;
 	bool pos_dirty;
+	struct weston_output_weak_ref legacy_fullscreen_output;
 	int saved_width, saved_height;
 	int decorate;
 	int override_redirect;
@@ -170,6 +177,11 @@ weston_wm_set_net_active_window(struct weston_wm *wm, xcb_window_t window);
 static void
 weston_wm_window_schedule_repaint(struct weston_wm_window *window);
 
+static int
+legacy_fullscreen(struct weston_wm *wm,
+		  struct weston_wm_window *window,
+		  struct weston_output **output_ret);
+
 static void
 xserver_map_shell_surface(struct weston_wm_window *window,
 			  struct weston_surface *surface);
@@ -208,6 +220,47 @@ wm_log_continue(const char *fmt, ...)
 #endif
 }
 
+static void
+weston_output_weak_ref_init(struct weston_output_weak_ref *ref)
+{
+	ref->output = NULL;
+}
+
+static void
+weston_output_weak_ref_clear(struct weston_output_weak_ref *ref)
+{
+	if (!ref->output)
+		return;
+
+	wl_list_remove(&ref->destroy_listener.link);
+	ref->output = NULL;
+}
+
+static void
+weston_output_weak_ref_handle_destroy(struct wl_listener *listener, void *data)
+{
+	struct weston_output_weak_ref *ref;
+
+	ref = wl_container_of(listener, ref, destroy_listener);
+	assert(ref->output == data);
+
+	weston_output_weak_ref_clear(ref);
+}
+
+static void
+weston_output_weak_ref_set(struct weston_output_weak_ref *ref,
+			   struct weston_output *output)
+{
+	weston_output_weak_ref_clear(ref);
+
+	if (!output)
+		return;
+
+	ref->destroy_listener.notify = weston_output_weak_ref_handle_destroy;
+	wl_signal_add(&output->destroy_signal, &ref->destroy_listener);
+	ref->output = output;
+}
+
 static bool __attribute__ ((warn_unused_result))
 wm_lookup_window(struct weston_wm *wm, xcb_window_t hash,
 		 struct weston_wm_window **window)
@@ -951,6 +1004,7 @@ weston_wm_handle_map_request(struct weston_wm *wm, xcb_generic_event_t *event)
 	xcb_map_request_event_t *map_request =
 		(xcb_map_request_event_t *) event;
 	struct weston_wm_window *window;
+	struct weston_output *output;
 
 	if (our_resource(wm, map_request->window)) {
 		wm_log("XCB_MAP_REQUEST (window %d, ours)\n",
@@ -974,6 +1028,12 @@ weston_wm_handle_map_request(struct weston_wm *wm, xcb_generic_event_t *event)
 	weston_wm_window_set_net_wm_state(window);
 	weston_wm_window_set_virtual_desktop(window, 0);
 
+	if (legacy_fullscreen(wm, window, &output)) {
+		window->fullscreen = 1;
+		weston_output_weak_ref_set(&window->legacy_fullscreen_output,
+					   output);
+	}
+
 	xcb_map_window(wm->conn, map_request->window);
 	xcb_map_window(wm->conn, window->frame_id);
 }
@@ -1206,6 +1266,7 @@ weston_wm_window_create(struct weston_wm *wm,
 	window->x = x;
 	window->y = y;
 	window->pos_dirty = false;
+	weston_output_weak_ref_init(&window->legacy_fullscreen_output);
 
 	geometry_reply = xcb_get_geometry_reply(wm->conn, geometry_cookie, NULL);
 	/* technically we should use XRender and check the visual format's
@@ -1222,6 +1283,8 @@ weston_wm_window_destroy(struct weston_wm_window *window)
 {
 	struct weston_wm *wm = window->wm;
 
+	weston_output_weak_ref_clear(&window->legacy_fullscreen_output);
+
 	if (window->repaint_source)
 		wl_event_source_remove(window->repaint_source);
 	if (window->cairo_surface)
@@ -2521,7 +2584,6 @@ xserver_map_shell_surface(struct weston_wm_window *window,
 		wm->server->compositor->xwayland;
 	const struct weston_desktop_xwayland_interface *xwayland_interface =
 		wm->server->compositor->xwayland_interface;
-	struct weston_output *output;
 	struct weston_wm_window *parent;
 
 	weston_wm_window_read_properties(window);
@@ -2565,11 +2627,9 @@ xserver_map_shell_surface(struct weston_wm_window *window,
 	if (window->fullscreen) {
 		window->saved_width = window->width;
 		window->saved_height = window->height;
-		xwayland_interface->set_fullscreen(window->shsurf, NULL);
+		xwayland_interface->set_fullscreen(window->shsurf,
+						   window->legacy_fullscreen_output.output);
 		return;
-	} else if (legacy_fullscreen(wm, window, &output)) {
-		window->fullscreen = 1;
-		xwayland_interface->set_fullscreen(window->shsurf, output);
 	} else if (window->override_redirect) {
 		xwayland_interface->set_xwayland(window->shsurf,
 						 window->x, window->y);