wayland/surface: Prepare for decoupled surface & resource lifetimes

Need to deal with surface->resource == NULL and
surface->pending_state == NULL in some places.

v2:
* Avoid expanding conditions to multiple lines.
  (Georges Basile Stavracas Neto)
v3:
* Use a single bailout condition in meta_wayland_client_owns_window as
  well.
v4:
* Remove spare empty line in meta_wayland_surface_apply_state.
  (Robert Mader)
* Add wl_resource_post_error calls in xdg-shell request handlers.
  (Robert Mader)
* Drop checks in functions which can only be called if there's a valid
  resource.
* Drop more checks which are unnecessary due to leaving the
  SURFACE_DESTROY signal emission in wl_surface_destructor later.
v5:
* Move resource = surface->resource assignments to if (!resource) tests.
  (Jonas Ådahl)
v6:
* Fix style issue per check-style.py.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1880>

src/wayland/meta-wayland-client.c

@@ -298,7 +298,7 @@ meta_wayland_client_owns_window (MetaWaylandClient *client,
   g_return_val_if_fail (client->process_running, FALSE);
 
   surface = meta_window_get_wayland_surface (window);
-  if (surface == NULL)
+  if (surface == NULL || surface->resource == NULL)
     return FALSE;
 
   return wl_resource_get_client (surface->resource) == client->wayland_client;

src/wayland/meta-wayland-surface.c

@@ -769,10 +769,13 @@ meta_wayland_surface_apply_state (MetaWaylandSurface      *surface,
                                            &error))
             {
               g_warning ("Could not import pending buffer: %s", error->message);
-              wl_resource_post_error (surface->resource, WL_DISPLAY_ERROR_NO_MEMORY,
-                                      "Failed to attach buffer to surface %i: %s",
-                                      wl_resource_get_id (surface->resource),
-                                      error->message);
+              if (surface->resource)
+                {
+                  wl_resource_post_error (surface->resource, WL_DISPLAY_ERROR_NO_MEMORY,
+                                          "Failed to attach buffer to surface %i: %s",
+                                          wl_resource_get_id (surface->resource),
+                                          error->message);
+                }
               g_error_free (error);
               goto cleanup;
             }
@@ -1330,21 +1333,24 @@ static void
 surface_entered_output (MetaWaylandSurface *surface,
                         MetaWaylandOutput *wayland_output)
 {
-  const GList *l;
-
   g_signal_connect (wayland_output, "output-destroyed",
                     G_CALLBACK (handle_output_destroyed),
                     surface);
 
-  for (l = meta_wayland_output_get_resources (wayland_output); l; l = l->next)
+  if (surface->resource)
     {
-      struct wl_resource *resource = l->data;
+      const GList *l;
 
-      if (wl_resource_get_client (resource) !=
-          wl_resource_get_client (surface->resource))
-        continue;
+      for (l = meta_wayland_output_get_resources (wayland_output); l; l = l->next)
+        {
+          struct wl_resource *resource = l->data;
 
-      wl_surface_send_enter (surface->resource, resource);
+          if (wl_resource_get_client (resource) !=
+              wl_resource_get_client (surface->resource))
+            continue;
+
+          wl_surface_send_enter (surface->resource, resource);
+        }
     }
 
   g_signal_connect (wayland_output, "output-bound",
@@ -1366,6 +1372,9 @@ surface_left_output (MetaWaylandSurface *surface,
                                         G_CALLBACK (handle_output_bound),
                                         surface);
 
+  if (!surface->resource)
+    return;
+
   for (l = meta_wayland_output_get_resources (wayland_output); l; l = l->next)
     {
       struct wl_resource *resource = l->data;

src/wayland/meta-wayland-tablet-pad.c

@@ -466,7 +466,7 @@ meta_wayland_tablet_pad_set_focus (MetaWaylandTabletPad *pad,
   tablet = meta_wayland_tablet_seat_lookup_paired_tablet (pad->tablet_seat,
                                                           pad);
 
-  if (tablet != NULL && surface != NULL)
+  if (tablet != NULL && surface != NULL && surface->resource != NULL)
     {
       struct wl_client *client;
 

src/wayland/meta-wayland-text-input.c

@@ -371,7 +371,7 @@ meta_wayland_text_input_set_focus (MetaWaylandTextInput *text_input,
       text_input->surface = NULL;
     }
 
-  if (surface)
+  if (surface && surface->resource)
     {
       struct wl_resource *focus_surface_resource;
 

src/wayland/meta-wayland-touch.c

@@ -227,7 +227,7 @@ meta_wayland_touch_update (MetaWaylandTouch   *touch,
       if (META_IS_SURFACE_ACTOR_WAYLAND (actor))
         surface = meta_surface_actor_wayland_get_surface (META_SURFACE_ACTOR_WAYLAND (actor));
 
-      if (!surface)
+      if (!surface || !surface->resource)
         return;
 
       touch_info = touch_get_info (touch, sequence, TRUE);

src/wayland/meta-wayland-viewporter.c

@@ -46,10 +46,13 @@ wp_viewport_destructor (struct wl_resource *resource)
   g_clear_signal_handler (&surface->viewport.destroy_handler_id, surface);
 
   pending = meta_wayland_surface_get_pending_state (surface);
-  pending->viewport_src_rect.size.width = -1;
-  pending->viewport_dst_width = -1;
-  pending->has_new_viewport_src_rect = TRUE;
-  pending->has_new_viewport_dst_size = TRUE;
+  if (pending)
+    {
+      pending->viewport_src_rect.size.width = -1;
+      pending->viewport_dst_width = -1;
+      pending->has_new_viewport_src_rect = TRUE;
+      pending->has_new_viewport_dst_size = TRUE;
+    }
 
   surface->viewport.resource = NULL;
 }
@@ -103,6 +106,14 @@ wp_viewport_set_source (struct wl_client   *client,
       MetaWaylandSurfaceState *pending;
 
       pending = meta_wayland_surface_get_pending_state (surface);
+      if (!pending)
+        {
+          wl_resource_post_error (resource,
+                                  WP_VIEWPORT_ERROR_NO_SURFACE,
+                                  "wl_surface for this viewport no longer exists");
+          return;
+        }
+
       pending->viewport_src_rect.origin.x = new_x;
       pending->viewport_src_rect.origin.y = new_y;
       pending->viewport_src_rect.size.width = new_width;
@@ -142,6 +153,14 @@ wp_viewport_set_destination (struct wl_client   *client,
       MetaWaylandSurfaceState *pending;
 
       pending = meta_wayland_surface_get_pending_state (surface);
+      if (!pending)
+        {
+          wl_resource_post_error (resource,
+                                  WP_VIEWPORT_ERROR_NO_SURFACE,
+                                  "wl_surface for this viewport no longer exists");
+          return;
+        }
+
       pending->viewport_dst_width = dst_width;
       pending->viewport_dst_height = dst_height;
       pending->has_new_viewport_dst_size = TRUE;

src/wayland/meta-wayland-xdg-shell.c

@@ -391,6 +391,14 @@ xdg_toplevel_set_max_size (struct wl_client   *client,
 
 
   pending = meta_wayland_surface_get_pending_state (surface);
+  if (!pending)
+    {
+      wl_resource_post_error (resource,
+                              XDG_WM_BASE_ERROR_INVALID_SURFACE_STATE,
+                              "underlying wl_surface already destroyed");
+      return;
+    }
+
   pending->has_new_max_size = TRUE;
   pending->new_max_width = width;
   pending->new_max_height = height;
@@ -416,6 +424,14 @@ xdg_toplevel_set_min_size (struct wl_client   *client,
 
 
   pending = meta_wayland_surface_get_pending_state (surface);
+  if (!pending)
+    {
+      wl_resource_post_error (resource,
+                              XDG_WM_BASE_ERROR_INVALID_SURFACE_STATE,
+                              "underlying wl_surface already destroyed");
+      return;
+    }
+
   pending->has_new_min_size = TRUE;
   pending->new_min_width = width;
   pending->new_min_height = height;
@@ -873,9 +889,12 @@ meta_wayland_xdg_toplevel_post_apply_state (MetaWaylandSurfaceRole  *surface_rol
         }
       else
         {
-          wl_resource_post_error (surface->resource,
-                                  XDG_WM_BASE_ERROR_INVALID_SURFACE_STATE,
-                                  "Invalid min/max size");
+          if (surface->resource)
+            {
+              wl_resource_post_error (surface->resource,
+                                      XDG_WM_BASE_ERROR_INVALID_SURFACE_STATE,
+                                      "Invalid min/max size");
+            }
         }
     }
 }
@@ -1556,6 +1575,14 @@ xdg_surface_set_window_geometry (struct wl_client   *client,
     }
 
   pending = meta_wayland_surface_get_pending_state (surface);
+  if (!pending)
+    {
+      wl_resource_post_error (resource,
+                              XDG_WM_BASE_ERROR_INVALID_SURFACE_STATE,
+                              "underlying wl_surface already destroyed");
+      return;
+    }
+
   pending->has_new_geometry = TRUE;
   pending->new_geometry.x = x;
   pending->new_geometry.y = y;
@@ -1572,6 +1599,14 @@ xdg_surface_ack_configure (struct wl_client   *client,
   MetaWaylandSurfaceState *pending;
 
   pending = meta_wayland_surface_get_pending_state (surface);
+  if (!pending)
+    {
+      wl_resource_post_error (resource,
+                              XDG_WM_BASE_ERROR_INVALID_SURFACE_STATE,
+                              "underlying wl_surface already destroyed");
+      return;
+    }
+
   pending->has_acked_configure_serial = TRUE;
   pending->acked_configure_serial = serial;
 }

src/wayland/meta-window-wayland.c

@@ -162,7 +162,11 @@ static void
 meta_window_wayland_kill (MetaWindow *window)
 {
   MetaWaylandSurface *surface = meta_window_get_wayland_surface (window);
-  struct wl_resource *resource = surface->resource;
+  struct wl_resource *resource;
+
+  resource = surface->resource;
+  if (!resource)
+    return;
 
   /* Send the client an unrecoverable error to kill the client. */
   wl_resource_post_error (resource,
@@ -659,9 +663,13 @@ static pid_t
 meta_window_wayland_get_client_pid (MetaWindow *window)
 {
   MetaWaylandSurface *surface = meta_window_get_wayland_surface (window);
-  struct wl_resource *resource = surface->resource;
+  struct wl_resource *resource;
   pid_t pid;
 
+  resource = surface->resource;
+  if (!resource)
+    return 0;
+
   wl_client_get_credentials (wl_resource_get_client (resource), &pid, NULL, NULL);
   return pid;
 }

src/wayland/meta-xwayland.c

@@ -137,7 +137,8 @@ meta_xwayland_is_xwayland_surface (MetaWaylandSurface *surface)
   MetaWaylandCompositor *compositor = meta_wayland_compositor_get_default ();
   MetaXWaylandManager *manager = &compositor->xwayland_manager;
 
-  return wl_resource_get_client (surface->resource) == manager->client;
+  return surface->resource != NULL &&
+         wl_resource_get_client (surface->resource) == manager->client;
 }
 
 static gboolean