wayland/surface: Call meta_wayland_buffer_attach from surface commit

Preparation for potentially calling meta_wayland_transaction_apply some
time after surface commit, in which case doing it in the former would be
too late: The client may legally destroy the attached wl_buffer
immediately after commit, in which case meta_wayland_buffer_attach would
spuriously fail and disconnect the client (or possibly even crash mutter
due to NULL error).

Requires splitting up the surface texture between protocol and output
state, and propagating from the former to the latter via
MetaWaylandSurfaceState.

v2: (Jonas Ådahl)
* Move meta_wayland_surface_get_texture call to separate line.
* Use g_autoptr for GError.

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

src/wayland/meta-wayland-actor-surface.c

@@ -189,11 +189,13 @@ meta_wayland_actor_surface_real_sync_actor_state (MetaWaylandActorSurface *actor
     {
       CoglSnippet *snippet;
       gboolean is_y_inverted;
+      CoglTexture *texture;
 
       snippet = meta_wayland_buffer_create_snippet (buffer);
       is_y_inverted = meta_wayland_buffer_is_y_inverted (buffer);
 
-      meta_shaped_texture_set_texture (stex, surface->texture);
+      texture = meta_wayland_surface_get_texture (surface);
+      meta_shaped_texture_set_texture (stex, texture);
       meta_shaped_texture_set_snippet (stex, snippet);
       meta_shaped_texture_set_is_y_inverted (stex, is_y_inverted);
       meta_shaped_texture_set_buffer_scale (stex, surface->scale);

src/wayland/meta-wayland-buffer.c

@@ -561,8 +561,6 @@ meta_wayland_buffer_attach (MetaWaylandBuffer  *buffer,
                             CoglTexture       **texture,
                             GError            **error)
 {
-  g_return_val_if_fail (buffer->resource, FALSE);
-
   COGL_TRACE_BEGIN_SCOPED (MetaWaylandBufferAttach, "WaylandBuffer (attach)");
 
   if (!meta_wayland_buffer_is_realized (buffer))

src/wayland/meta-wayland-surface.c

@@ -311,7 +311,7 @@ get_buffer_width (MetaWaylandSurface *surface)
   MetaWaylandBuffer *buffer = meta_wayland_surface_get_buffer (surface);
 
   if (buffer)
-    return cogl_texture_get_width (surface->texture);
+    return cogl_texture_get_width (surface->output_state.texture);
   else
     return 0;
 }
@@ -322,7 +322,7 @@ get_buffer_height (MetaWaylandSurface *surface)
   MetaWaylandBuffer *buffer = meta_wayland_surface_get_buffer (surface);
 
   if (buffer)
-    return cogl_texture_get_height (surface->texture);
+    return cogl_texture_get_height (surface->output_state.texture);
   else
     return 0;
 }
@@ -418,7 +418,8 @@ surface_process_damage (MetaWaylandSurface *surface,
 
   cairo_region_intersect_rectangle (buffer_region, &buffer_rect);
 
-  meta_wayland_buffer_process_damage (buffer, surface->texture, buffer_region);
+  meta_wayland_buffer_process_damage (buffer, surface->output_state.texture,
+                                      buffer_region);
 
   actor = meta_wayland_surface_get_actor (surface);
   if (actor)
@@ -469,6 +470,7 @@ meta_wayland_surface_state_set_default (MetaWaylandSurfaceState *state)
 {
   state->newly_attached = FALSE;
   state->buffer = NULL;
+  state->texture = NULL;
   state->buffer_destroy_handler_id = 0;
   state->dx = 0;
   state->dy = 0;
@@ -514,6 +516,8 @@ meta_wayland_surface_state_clear (MetaWaylandSurfaceState *state)
 {
   MetaWaylandFrameCallback *cb, *next;
 
+  cogl_clear_object (&state->texture);
+
   g_clear_pointer (&state->surface_damage, cairo_region_destroy);
   g_clear_pointer (&state->buffer_damage, cairo_region_destroy);
   g_clear_pointer (&state->input_region, cairo_region_destroy);
@@ -549,6 +553,9 @@ meta_wayland_surface_state_merge_into (MetaWaylandSurfaceState *from,
 
       to->newly_attached = TRUE;
       to->buffer = from->buffer;
+
+      cogl_clear_object (&to->texture);
+      to->texture = g_steal_pointer (&from->texture);
     }
 
   to->dx += from->dx;
@@ -799,30 +806,8 @@ meta_wayland_surface_apply_state (MetaWaylandSurface      *surface,
       if (state->buffer)
         meta_wayland_surface_ref_buffer_use_count (surface);
 
-      if (state->buffer)
+      cogl_clear_object (&surface->output_state.texture);
-        {
+      surface->output_state.texture = g_steal_pointer (&state->texture);
-          GError *error = NULL;
-
-          if (!meta_wayland_buffer_attach (state->buffer,
-                                           &surface->texture,
-                                           &error))
-            {
-              g_warning ("Could not import pending buffer: %s", 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;
-            }
-        }
-      else
-        {
-          cogl_clear_object (&surface->texture);
-        }
 
       /* If the newly attached buffer is going to be accessed directly without
        * making a copy, such as an EGL buffer, mark it as in-use don't release
@@ -949,7 +934,6 @@ meta_wayland_surface_apply_state (MetaWaylandSurface      *surface,
   if (state->subsurface_placement_ops)
     meta_wayland_surface_notify_subsurface_state_changed (surface);
 
-cleanup:
   /* If we have a buffer that we are not using, decrease the use count so it may
    * be released if no-one else has a use-reference to it.
    */
@@ -1000,15 +984,39 @@ static void
 meta_wayland_surface_commit (MetaWaylandSurface *surface)
 {
   MetaWaylandSurfaceState *pending = surface->pending_state;
+  MetaWaylandBuffer *buffer = pending->buffer;
   MetaWaylandTransaction *transaction;
   MetaWaylandSurface *subsurface_surface;
 
   COGL_TRACE_BEGIN_SCOPED (MetaWaylandSurfaceCommit,
                            "WaylandSurface (commit)");
 
-  if (pending->buffer &&
+  if (buffer)
-      !meta_wayland_buffer_is_realized (pending->buffer))
+    {
-    meta_wayland_buffer_realize (pending->buffer);
+      g_autoptr (GError) error = NULL;
+
+      if (!meta_wayland_buffer_is_realized (buffer))
+        meta_wayland_buffer_realize (buffer);
+
+      if (!meta_wayland_buffer_attach (buffer,
+                                       &surface->protocol_state.texture,
+                                       &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);
+          return;
+        }
+
+      pending->texture = cogl_object_ref (surface->protocol_state.texture);
+    }
+  else if (pending->newly_attached)
+    {
+      cogl_clear_object (&surface->protocol_state.texture);
+    }
 
   if (meta_wayland_surface_is_synchronized (surface))
     transaction = meta_wayland_surface_ensure_transaction (surface);
@@ -1483,7 +1491,7 @@ meta_wayland_surface_finalize (GObject *object)
 
   if (surface->buffer_held)
     meta_wayland_surface_unref_buffer_use_count (surface);
-  g_clear_pointer (&surface->texture, cogl_object_unref);
+  g_clear_pointer (&surface->output_state.texture, cogl_object_unref);
   g_clear_pointer (&surface->buffer_ref, meta_wayland_buffer_ref_unref);
 
   if (surface->opaque_region)
@@ -1535,6 +1543,8 @@ wl_surface_destructor (struct wl_resource *resource)
   g_clear_pointer (&surface->wl_subsurface, wl_resource_destroy);
   g_clear_pointer (&surface->protocol_state.subsurface_branch_node, g_node_destroy);
 
+  cogl_clear_object (&surface->protocol_state.texture);
+
   /*
    * Any transactions referencing this surface will keep it alive until they get
    * applied/destroyed. The last reference will be dropped in
@@ -2117,7 +2127,7 @@ meta_wayland_surface_is_shortcuts_inhibited (MetaWaylandSurface *surface,
 CoglTexture *
 meta_wayland_surface_get_texture (MetaWaylandSurface *surface)
 {
-  return surface->texture;
+  return surface->output_state.texture;
 }
 
 MetaSurfaceActor *

src/wayland/meta-wayland-surface.h

@@ -80,6 +80,7 @@ struct _MetaWaylandSurfaceState
   /* wl_surface.attach */
   gboolean newly_attached;
   MetaWaylandBuffer *buffer;
+  CoglTexture *texture;
   gulong buffer_destroy_handler_id;
   int32_t dx;
   int32_t dy;
@@ -169,8 +170,6 @@ struct _MetaWaylandSurface
   GHashTable *outputs;
   MetaMonitorTransform buffer_transform;
 
-  CoglTexture *texture;
-
   /* Buffer reference state. */
   MetaWaylandBufferRef *buffer_ref;
 
@@ -194,6 +193,7 @@ struct _MetaWaylandSurface
     MetaWaylandSurface *parent;
     GNode *subsurface_branch_node;
     GNode *subsurface_leaf_node;
+    CoglTexture *texture;
   } output_state, protocol_state;
 
   /* Extension resources. */