shell: wait for desktop-shell init before fade in

On Raspberry Pi, weston-desktop-shell is so slow to start, that the
compositor has time to run the fade-in before the wallpaper is up. The
user launching Weston sees the screen flipping to black, the fbcon
fading in, and then the desktop popping up.

To fix this, wait for the weston-desktop-shell to draw
everything before starting the initial fade-in. A new request is
added to the private desktop-shell protocol to signal it. If a
desktop-shell client does not support the new request, the fade-in
happens already at bind time.

If weston-desktop-shell crashes, or does not send the 'desktop_ready'
request in 15 seconds, the compositor will fade in anyway. This should
avoid a blocked screen in case weston-desktop-shell malfunction.

shell_fade_startup() does not directly start the fade-in but schedules
an idle callback, so that the compositor can process all pending events
before starting the fade clock. Otherwise (on RPi) we risk skipping part
of the animation. Yes, it is a hack, that should have been done in
window.c and weston-desktop-shell instead.

Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>

src/shell.c

@@ -156,6 +156,7 @@ struct desktop_shell {
 		struct weston_surface *surface;
 		struct weston_surface_animation *animation;
 		enum fade_type type;
+		struct wl_event_source *startup_timer;
 	} fade;
 
 	uint32_t binding_modifier;
@@ -275,6 +276,9 @@ shell_surface_get_shell(struct shell_surface *shsurf);
 static void
 surface_rotate(struct shell_surface *surface, struct weston_seat *seat);
 
+static void
+shell_fade_startup(struct desktop_shell *shell);
+
 static bool
 shell_surface_is_top_fullscreen(struct shell_surface *shsurf)
 {
@@ -2548,12 +2552,22 @@ desktop_shell_set_grab_surface(struct wl_client *client,
 	shell->grab_surface = surface_resource->data;
 }
 
+static void
+desktop_shell_desktop_ready(struct wl_client *client,
+			    struct wl_resource *resource)
+{
+	struct desktop_shell *shell = resource->data;
+
+	shell_fade_startup(shell);
+}
+
 static const struct desktop_shell_interface desktop_shell_implementation = {
 	desktop_shell_set_background,
 	desktop_shell_set_panel,
 	desktop_shell_set_lock_surface,
 	desktop_shell_unlock,
-	desktop_shell_set_grab_surface
+	desktop_shell_set_grab_surface,
+	desktop_shell_desktop_ready
 };
 
 static enum shell_surface_type
@@ -3031,11 +3045,28 @@ shell_fade_done(struct weston_surface_animation *animation, void *data)
 	}
 }
 
-static void
-shell_fade(struct desktop_shell *shell, enum fade_type type)
+static struct weston_surface *
+shell_fade_create_surface(struct desktop_shell *shell)
 {
 	struct weston_compositor *compositor = shell->compositor;
 	struct weston_surface *surface;
+
+	surface = weston_surface_create(compositor);
+	if (!surface)
+		return NULL;
+
+	weston_surface_configure(surface, 0, 0, 8192, 8192);
+	weston_surface_set_color(surface, 0.0, 0.0, 0.0, 1.0);
+	wl_list_insert(&compositor->fade_layer.surface_list,
+		       &surface->layer_link);
+	pixman_region32_init(&surface->input);
+
+	return surface;
+}
+
+static void
+shell_fade(struct desktop_shell *shell, enum fade_type type)
+{
 	float tint;
 
 	switch (type) {
@@ -3053,18 +3084,12 @@ shell_fade(struct desktop_shell *shell, enum fade_type type)
 	shell->fade.type = type;
 
 	if (shell->fade.surface == NULL) {
-		surface = weston_surface_create(compositor);
-		if (!surface)
+		shell->fade.surface = shell_fade_create_surface(shell);
+		if (!shell->fade.surface)
 			return;
 
-		weston_surface_configure(surface, 0, 0, 8192, 8192);
-		weston_surface_set_color(surface, 0.0, 0.0, 0.0, 1.0);
-		surface->alpha = 1.0 - tint;
-		wl_list_insert(&compositor->fade_layer.surface_list,
-			       &surface->layer_link);
-		weston_surface_update_transform(surface);
-		shell->fade.surface = surface;
-		pixman_region32_init(&surface->input);
+		shell->fade.surface->alpha = 1.0 - tint;
+		weston_surface_update_transform(shell->fade.surface);
 	}
 
 	if (shell->fade.animation)
@@ -3077,6 +3102,67 @@ shell_fade(struct desktop_shell *shell, enum fade_type type)
 					shell_fade_done, shell);
 }
 
+static void
+do_shell_fade_startup(void *data)
+{
+	struct desktop_shell *shell = data;
+
+	shell_fade(shell, FADE_IN);
+}
+
+static void
+shell_fade_startup(struct desktop_shell *shell)
+{
+	struct wl_event_loop *loop;
+
+	if (!shell->fade.startup_timer)
+		return;
+
+	wl_event_source_remove(shell->fade.startup_timer);
+	shell->fade.startup_timer = NULL;
+
+	loop = wl_display_get_event_loop(shell->compositor->wl_display);
+	wl_event_loop_add_idle(loop, do_shell_fade_startup, shell);
+}
+
+static int
+fade_startup_timeout(void *data)
+{
+	struct desktop_shell *shell = data;
+
+	shell_fade_startup(shell);
+	return 0;
+}
+
+static void
+shell_fade_init(struct desktop_shell *shell)
+{
+	/* Make compositor output all black, and wait for the desktop-shell
+	 * client to signal it is ready, then fade in. The timer triggers a
+	 * fade-in, in case the desktop-shell client takes too long.
+	 */
+
+	struct wl_event_loop *loop;
+
+	if (shell->fade.surface != NULL) {
+		weston_log("%s: warning: fade surface already exists\n",
+			   __func__);
+		return;
+	}
+
+	shell->fade.surface = shell_fade_create_surface(shell);
+	if (!shell->fade.surface)
+		return;
+
+	weston_surface_update_transform(shell->fade.surface);
+	weston_surface_damage(shell->fade.surface);
+
+	loop = wl_display_get_event_loop(shell->compositor->wl_display);
+	shell->fade.startup_timer =
+		wl_event_loop_add_timer(loop, fade_startup_timeout, shell);
+	wl_event_source_timer_update(shell->fade.startup_timer, 15000);
+}
+
 static void
 idle_handler(struct wl_listener *listener, void *data)
 {
@@ -3444,6 +3530,7 @@ desktop_shell_sigchld(struct weston_process *process, int status)
 
 	weston_log("weston-desktop-shell died, respawning...\n");
 	launch_desktop_shell_process(shell);
+	shell_fade_startup(shell);
 }
 
 static void
@@ -3497,6 +3584,10 @@ bind_desktop_shell(struct wl_client *client,
 	if (client == shell->child.client) {
 		resource->destroy = unbind_desktop_shell;
 		shell->child.desktop_shell = resource;
+
+		if (version < 2)
+			shell_fade_startup(shell);
+
 		return;
 	}
 
@@ -4391,7 +4482,7 @@ module_init(struct weston_compositor *ec,
 
 	shell_add_bindings(ec, shell);
 
-	shell_fade(shell, FADE_IN);
+	shell_fade_init(shell);
 
 	return 0;
 }