shell: Inhibit idle fade-out behavior

When a client has registered idle inhibition on a surface, don't trigger
the fade-out animation on the output(s) the surface is displayed on.
But when the surface is destroyed or the inhibitor itself is destroyed
by client request, re-queue the fade out animation.

desktop-shell/shell.c

@@ -2279,6 +2279,7 @@ fade_out_done(struct weston_view_animation *animation, void *data)
 	}
 }
 
+/** Re-queue the fade animation to be evaluated if client had been inhibiting */
 struct shell_surface *
 get_shell_surface(struct weston_surface *surface)
 {
@@ -2294,6 +2295,26 @@ get_shell_surface(struct weston_surface *surface)
  * libweston-desktop
  */
 
+static void
+desktop_surface_drop_idle_inhibitor(struct weston_desktop_surface *desktop_surface,
+				    void *shell)
+{
+	struct shell_surface *shsurf =
+		weston_desktop_surface_get_user_data(desktop_surface);
+	struct weston_surface *surface =
+		weston_desktop_surface_get_surface(desktop_surface);
+	struct weston_compositor *compositor =
+		shsurf->shell->compositor;
+
+	if (compositor->state == WESTON_COMPOSITOR_IDLE
+	     || compositor->state == WESTON_COMPOSITOR_OFFSCREEN
+	     || compositor->state == WESTON_COMPOSITOR_SLEEPING)
+	{
+		surface->inhibit_idling = false;
+		shell_fade(shsurf->shell, FADE_OUT);
+	}
+}
+
 static void
 desktop_surface_added(struct weston_desktop_surface *desktop_surface,
 		      void *shell)
@@ -2358,6 +2379,9 @@ desktop_surface_removed(struct weston_desktop_surface *desktop_surface,
 	if (!shsurf)
 		return;
 
+	if (surface->inhibit_idling)
+		desktop_surface_drop_idle_inhibitor(desktop_surface, shell);
+
 	wl_signal_emit(&shsurf->destroy_signal, shsurf);
 
 	if (shsurf->fullscreen.black_view)
@@ -2774,6 +2798,7 @@ static const struct weston_desktop_api shell_desktop_api = {
 	.struct_size = sizeof(struct weston_desktop_api),
 	.surface_added = desktop_surface_added,
 	.surface_removed = desktop_surface_removed,
+	.surface_drop_idle_inhibitor = desktop_surface_drop_idle_inhibitor,
 	.committed = desktop_surface_committed,
 	.move = desktop_surface_move,
 	.resize = desktop_surface_resize,
@@ -3823,6 +3848,7 @@ shell_fade(struct desktop_shell *shell, enum fade_type type)
 {
 	float tint;
 	struct shell_output *shell_output;
+	uint32_t inhibit_mask = weston_compositor_inhibited_outputs(shell->compositor);
 
 	switch (type) {
 	case FADE_IN:
@@ -3837,6 +3863,9 @@ shell_fade(struct desktop_shell *shell, enum fade_type type)
 
 	/* Create a separate fade surface for each output */
 	wl_list_for_each(shell_output, &shell->output_list, link) {
+		if (inhibit_mask & (1 << shell_output->output->id))
+			continue;
+
 		shell_output->fade.type = type;
 
 		if (shell_output->fade.view == NULL) {
@@ -3932,12 +3961,17 @@ shell_fade_init(struct desktop_shell *shell)
 		return;
 
 	wl_list_for_each(shell_output, &shell->output_list, link) {
+		uint32_t inhibit_mask = weston_compositor_inhibited_outputs(shell->compositor);
+
 		if (shell_output->fade.view != NULL) {
 			weston_log("%s: warning: fade surface already exists\n",
 				   __func__);
 			continue;
 		}
 
+		if (inhibit_mask & (1 << shell_output->output->id))
+			continue;
+
 		shell_output->fade.view = shell_fade_create_surface_for_output(shell, shell_output);
 		if (!shell_output->fade.view)
 			return;

libweston/compositor.c

@@ -3930,7 +3930,10 @@ bind_subcompositor(struct wl_client *client,
 				       compositor, NULL);
 }
 
-/** Set a DPMS mode on all of the compositor's outputs
+/** Apply a DPMS mode to the compositor's outputs.
+ *
+ * Outputs may skip setting the DPMS state if they are being used to
+ * display an surface that is requesting idle behaviors be inhibited.
  *
  * \param compositor The compositor instance
  * \param state The DPMS state the outputs will be set to