Check weston_head_from_resource for NULL return

If the compositor is disabling a weston_output,
weston_head_from_resource can return NULL, so the return code must be
checked where used.

Fixes #638

Signed-off-by: Joshua Watt <JPEWhacker@gmail.com>

desktop-shell/input-panel.c

@@ -285,14 +285,15 @@ input_panel_surface_set_toplevel(struct wl_client *client,
 	struct input_panel_surface *input_panel_surface =
 		wl_resource_get_user_data(resource);
 	struct desktop_shell *shell = input_panel_surface->shell;
-	struct weston_head *head;
+	struct weston_head *head = weston_head_from_resource(output_resource);
 
-	wl_list_insert(&shell->input_panel.surfaces,
-		       &input_panel_surface->link);
+	if (head) {
+		wl_list_insert(&shell->input_panel.surfaces,
+			&input_panel_surface->link);
 
-	head = weston_head_from_resource(output_resource);
-	input_panel_surface->output = head->output;
-	input_panel_surface->panel = 0;
+		input_panel_surface->output = head->output;
+		input_panel_surface->panel = 0;
+	}
 }
 
 static void

desktop-shell/shell.c

@@ -2890,6 +2890,7 @@ desktop_shell_set_background(struct wl_client *client,
 		wl_resource_get_user_data(surface_resource);
 	struct shell_output *sh_output;
 	struct weston_view *view, *next;
+	struct weston_head *head = weston_head_from_resource(output_resource);
 
 	if (surface->committed) {
 		wl_resource_post_error(surface_resource,
@@ -2898,6 +2899,9 @@ desktop_shell_set_background(struct wl_client *client,
 		return;
 	}
 
+	if (!head)
+		return;
+
 	wl_list_for_each_safe(view, next, &surface->views, surface_link)
 		weston_view_destroy(view);
 	view = weston_view_create(surface);
@@ -2905,7 +2909,7 @@ desktop_shell_set_background(struct wl_client *client,
 	surface->committed = background_committed;
 	surface->committed_private = shell;
 	weston_surface_set_label_func(surface, background_get_label);
-	surface->output = weston_head_from_resource(output_resource)->output;
+	surface->output = head->output;
 	weston_view_set_output(view, surface->output);
 
 	sh_output = find_shell_output_from_weston_output(shell, surface->output);
@@ -2995,6 +2999,7 @@ desktop_shell_set_panel(struct wl_client *client,
 		wl_resource_get_user_data(surface_resource);
 	struct weston_view *view, *next;
 	struct shell_output *sh_output;
+	struct weston_head *head = weston_head_from_resource(output_resource);
 
 	if (surface->committed) {
 		wl_resource_post_error(surface_resource,
@@ -3003,6 +3008,9 @@ desktop_shell_set_panel(struct wl_client *client,
 		return;
 	}
 
+	if (!head)
+		return;
+
 	wl_list_for_each_safe(view, next, &surface->views, surface_link)
 		weston_view_destroy(view);
 	view = weston_view_create(surface);
@@ -3010,7 +3018,7 @@ desktop_shell_set_panel(struct wl_client *client,
 	surface->committed = panel_committed;
 	surface->committed_private = shell;
 	weston_surface_set_label_func(surface, panel_get_label);
-	surface->output = weston_head_from_resource(output_resource)->output;
+	surface->output = head->output;
 	weston_view_set_output(view, surface->output);
 
 	sh_output = find_shell_output_from_weston_output(shell, surface->output);

fullscreen-shell/fullscreen-shell.c

@@ -699,7 +699,6 @@ fullscreen_shell_present_surface(struct wl_client *client,
 {
 	struct fullscreen_shell *shell =
 		wl_resource_get_user_data(resource);
-	struct weston_output *output;
 	struct weston_surface *surface;
 	struct weston_seat *seat;
 	struct fs_output *fsout;
@@ -720,8 +719,13 @@ fullscreen_shell_present_surface(struct wl_client *client,
 	}
 
 	if (output_res) {
-		output = weston_head_from_resource(output_res)->output;
-		fsout = fs_output_for_output(output);
+		struct weston_head *head =
+			weston_head_from_resource(output_res);
+
+		if (!head)
+			return;
+
+		fsout = fs_output_for_output(head->output);
 		fs_output_set_surface(fsout, surface, method, 0, 0);
 	} else {
 		replace_default_surface(shell, surface, method);
@@ -759,13 +763,15 @@ fullscreen_shell_present_surface_for_mode(struct wl_client *client,
 {
 	struct fullscreen_shell *shell =
 		wl_resource_get_user_data(resource);
-	struct weston_output *output;
 	struct weston_surface *surface;
 	struct weston_seat *seat;
 	struct fs_output *fsout;
+	struct weston_head *head = weston_head_from_resource(output_res);
 
-	output = weston_head_from_resource(output_res)->output;
-	fsout = fs_output_for_output(output);
+	if (!head)
+		return;
+
+	fsout = fs_output_for_output(head->output);
 
 	if (surface_res == NULL) {
 		fs_output_set_surface(fsout, NULL, 0, 0, 0);

ivi-shell/ivi-shell.c

@@ -878,8 +878,10 @@ input_panel_surface_set_toplevel(struct wl_client *client,
 
 	head = weston_head_from_resource(output_resource);
 
-	ipsurf->type = INPUT_PANEL_TOPLEVEL;
-	ipsurf->output = head->output;
+	if (head) {
+		ipsurf->type = INPUT_PANEL_TOPLEVEL;
+		ipsurf->output = head->output;
+	}
 }
 
 static void

libweston/desktop/xdg-shell-v6.c

@@ -513,8 +513,12 @@ weston_desktop_xdg_toplevel_protocol_set_fullscreen(struct wl_client *wl_client,
 		weston_desktop_surface_get_implementation_data(dsurface);
 	struct weston_output *output = NULL;
 
-	if (output_resource != NULL)
-		output = weston_head_from_resource(output_resource)->output;
+	if (output_resource != NULL) {
+		struct weston_head *head =
+			weston_head_from_resource(output_resource);
+		if (head)
+			output = head->output;
+	}
 
 	weston_desktop_xdg_toplevel_ensure_added(toplevel);
 	weston_desktop_api_fullscreen_requested(toplevel->base.desktop, dsurface,

libweston/desktop/xdg-shell.c

@@ -562,8 +562,12 @@ weston_desktop_xdg_toplevel_protocol_set_fullscreen(struct wl_client *wl_client,
 		weston_desktop_surface_get_implementation_data(dsurface);
 	struct weston_output *output = NULL;
 
-	if (output_resource != NULL)
-		output = weston_head_from_resource(output_resource)->output;
+	if (output_resource != NULL) {
+		struct weston_head *head =
+			weston_head_from_resource(output_resource);
+		if (head)
+			output = head->output;
+	}
 
 	weston_desktop_xdg_toplevel_ensure_added(toplevel);
 	weston_desktop_api_fullscreen_requested(toplevel->base.desktop, dsurface,