wayland/surface: Use transactions for applying committed states

A transaction contains the committed state for a surface, plus any
cached state for synchronized subsurfaces.

v2:
* Handle sub-surface positions separately from surface states.
v3:
* Sync child states only for surfaces with state in the transaction.
v4: (Jonas Ådahl)
* Drop unnecessary g_object_new call from wl_subsurface_set_desync. (me)
* Fix indentation & formatting in meta_wayland_surface_commit.
* Add meta_wayland_surface_state_new helper function.
* Fix alignment of meta_wayland_transaction_apply_subsurface_position
  parameters.
* Add curly braces around meta_wayland_transaction_sync_child_states
  call in meta_wayland_transaction_apply.
v5:
* Make meta_wayland_surface_state_new an inline function.

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

src/wayland/meta-wayland-subsurface.c

@@ -28,6 +28,7 @@
 #include "wayland/meta-wayland-actor-surface.h"
 #include "wayland/meta-wayland-buffer.h"
 #include "wayland/meta-wayland-surface.h"
+#include "wayland/meta-wayland-transaction.h"
 #include "wayland/meta-window-wayland.h"
 
 struct _MetaWaylandSubsurface
@@ -105,28 +106,6 @@ is_sibling (MetaWaylandSurface *surface,
   return surface != sibling && surface->sub.parent == sibling->sub.parent;
 }
 
-void
-meta_wayland_subsurface_parent_state_applied (MetaWaylandSubsurface *subsurface)
-{
-  MetaWaylandSurfaceRole *surface_role = META_WAYLAND_SURFACE_ROLE (subsurface);
-  MetaWaylandActorSurface *actor_surface =
-    META_WAYLAND_ACTOR_SURFACE (subsurface);
-  MetaWaylandSurface *surface =
-    meta_wayland_surface_role_get_surface (surface_role);
-
-  if (surface->sub.pending_pos)
-    {
-      surface->sub.x = surface->sub.pending_x;
-      surface->sub.y = surface->sub.pending_y;
-      surface->sub.pending_pos = FALSE;
-    }
-
-  if (meta_wayland_surface_is_synchronized (surface))
-    meta_wayland_surface_apply_cached_state (surface);
-
-  meta_wayland_actor_surface_sync_actor_state (actor_surface);
-}
-
 void
 meta_wayland_subsurface_union_geometry (MetaWaylandSubsurface *subsurface,
                                         int                    parent_x,
@@ -452,7 +431,13 @@ wl_subsurface_set_desync (struct wl_client   *client,
     meta_wayland_surface_is_synchronized (surface->sub.parent);
 
   if (!is_parent_effectively_synchronized)
-    meta_wayland_surface_apply_cached_state (surface);
+    {
+      MetaWaylandTransaction *transaction;
+
+      transaction = meta_wayland_transaction_new (surface->compositor);
+      meta_wayland_transaction_add_cached_states (transaction, surface);
+      meta_wayland_transaction_commit (transaction);
+    }
 
   surface->sub.synchronous = FALSE;
 }

src/wayland/meta-wayland-subsurface.h

@@ -44,8 +44,6 @@ typedef struct
   struct wl_listener sibling_destroy_listener;
 } MetaWaylandSubsurfacePlacementOp;
 
-void meta_wayland_subsurface_parent_state_applied (MetaWaylandSubsurface *subsurface);
-
 void meta_wayland_subsurface_union_geometry (MetaWaylandSubsurface *subsurface,
                                              int                    parent_x,
                                              int                    parent_y,

src/wayland/meta-wayland-surface.c

@@ -48,6 +48,7 @@
 #include "wayland/meta-wayland-region.h"
 #include "wayland/meta-wayland-seat.h"
 #include "wayland/meta-wayland-subsurface.h"
+#include "wayland/meta-wayland-transaction.h"
 #include "wayland/meta-wayland-viewporter.h"
 #include "wayland/meta-wayland-xdg-shell.h"
 #include "wayland/meta-window-wayland.h"
@@ -717,7 +718,6 @@ void
 meta_wayland_surface_apply_state (MetaWaylandSurface      *surface,
                                   MetaWaylandSurfaceState *state)
 {
-  MetaWaylandSurface *subsurface_surface;
   gboolean had_damage = FALSE;
   int old_width, old_height;
 
@@ -956,14 +956,6 @@ cleanup:
                  surface_state_signals[SURFACE_STATE_SIGNAL_APPLIED],
                  0);
 
-  META_WAYLAND_SURFACE_FOREACH_SUBSURFACE (surface, subsurface_surface)
-    {
-      MetaWaylandSubsurface *subsurface;
-
-      subsurface = META_WAYLAND_SUBSURFACE (subsurface_surface->role);
-      meta_wayland_subsurface_parent_state_applied (subsurface);
-    }
-
   if (had_damage)
     {
       MetaWindow *toplevel_window;
@@ -984,22 +976,6 @@ cleanup:
     meta_wayland_surface_role_post_apply_state (surface->role, state);
 }
 
-static void
-ensure_cached_state (MetaWaylandSurface *surface)
-{
-  if (!surface->cached_state)
-    surface->cached_state = g_object_new (META_TYPE_WAYLAND_SURFACE_STATE,
-                                          NULL);
-}
-
-void
-meta_wayland_surface_apply_cached_state (MetaWaylandSurface *surface)
-{
-  ensure_cached_state (surface);
-  meta_wayland_surface_apply_state (surface, surface->cached_state);
-  meta_wayland_surface_state_reset (surface->cached_state);
-}
-
 MetaWaylandSurfaceState *
 meta_wayland_surface_get_pending_state (MetaWaylandSurface *surface)
 {
@@ -1028,16 +1004,30 @@ meta_wayland_surface_commit (MetaWaylandSurface *surface)
    */
   if (meta_wayland_surface_is_synchronized (surface))
     {
-      ensure_cached_state (surface);
-
-      meta_wayland_surface_state_merge_into (pending, surface->cached_state);
+      if (surface->cached_state)
+        {
+          meta_wayland_surface_state_merge_into (pending, surface->cached_state);
+          meta_wayland_surface_state_reset (pending);
+        }
+      else
+        {
+          surface->cached_state = pending;
+          surface->pending_state = meta_wayland_surface_state_new ();
+        }
     }
   else
     {
-      meta_wayland_surface_apply_state (surface, surface->pending_state);
-    }
+      MetaWaylandTransaction *transaction;
 
-  meta_wayland_surface_state_reset (pending);
+      transaction = meta_wayland_transaction_new (surface->compositor);
+      meta_wayland_transaction_add_state (transaction, surface, pending);
+      if (surface->sub.pending_pos)
+          meta_wayland_transaction_add_subsurface_position (transaction, surface);
+      meta_wayland_transaction_add_cached_child_states (transaction, surface);
+      meta_wayland_transaction_commit (transaction);
+
+      surface->pending_state = meta_wayland_surface_state_new ();
+    }
 }
 
 static void
@@ -1745,7 +1735,7 @@ meta_wayland_surface_get_absolute_coordinates (MetaWaylandSurface *surface,
 static void
 meta_wayland_surface_init (MetaWaylandSurface *surface)
 {
-  surface->pending_state = g_object_new (META_TYPE_WAYLAND_SURFACE_STATE, NULL);
+  surface->pending_state = meta_wayland_surface_state_new ();
 
   surface->buffer_ref = meta_wayland_buffer_ref_new ();
 

src/wayland/meta-wayland-surface.h

@@ -276,7 +276,8 @@ void                meta_wayland_surface_apply_state (MetaWaylandSurface      *s
 MetaWaylandSurfaceState *
                     meta_wayland_surface_get_pending_state (MetaWaylandSurface *surface);
 
-void                meta_wayland_surface_apply_cached_state (MetaWaylandSurface *surface);
+MetaWaylandSurfaceState *
+                    meta_wayland_surface_ensure_cached_state (MetaWaylandSurface *surface);
 
 gboolean            meta_wayland_surface_assign_role (MetaWaylandSurface *surface,
                                                       GType               role_type,
@@ -386,6 +387,12 @@ meta_wayland_surface_can_scanout_untransformed (MetaWaylandSurface *surface,
 
 int meta_wayland_surface_get_geometry_scale (MetaWaylandSurface *surface);
 
+static inline MetaWaylandSurfaceState *
+meta_wayland_surface_state_new (void)
+{
+  return g_object_new (META_TYPE_WAYLAND_SURFACE_STATE, NULL);
+}
+
 static inline GNode *
 meta_get_next_subsurface_sibling (GNode *n)
 {

src/wayland/meta-wayland-transaction.c

@@ -41,6 +41,11 @@ struct _MetaWaylandTransaction
 typedef struct _MetaWaylandTransactionEntry
 {
   MetaWaylandSurfaceState *state;
+
+  /* Sub-surface position */
+  gboolean has_sub_pos;
+  int x;
+  int y;
 } MetaWaylandTransactionEntry;
 
 static MetaWaylandTransactionEntry *
@@ -66,6 +71,17 @@ meta_wayland_transaction_sync_child_states (MetaWaylandSurface *surface)
     }
 }
 
+static void
+meta_wayland_transaction_apply_subsurface_position (MetaWaylandSurface          *surface,
+                                                    MetaWaylandTransactionEntry *entry)
+{
+  if (!entry->has_sub_pos)
+    return;
+
+  surface->sub.x = entry->x;
+  surface->sub.y = entry->y;
+}
+
 static gboolean
 is_ancestor (MetaWaylandSurface *candidate,
              MetaWaylandSurface *reference)
@@ -149,11 +165,13 @@ meta_wayland_transaction_apply (MetaWaylandTransaction  *transaction,
                                 MetaWaylandTransaction **first_candidate)
 {
   g_autofree MetaWaylandSurface **surfaces = NULL;
+  g_autofree MetaWaylandSurfaceState **states = NULL;
   unsigned int num_surfaces;
   int i;
 
   surfaces = (MetaWaylandSurface **)
     g_hash_table_get_keys_as_array (transaction->entries, &num_surfaces);
+  states = g_new (MetaWaylandSurfaceState *, num_surfaces);
 
   /* Sort surfaces from ancestors to descendants */
   qsort (surfaces, num_surfaces, sizeof (MetaWaylandSurface *),
@@ -166,7 +184,10 @@ meta_wayland_transaction_apply (MetaWaylandTransaction  *transaction,
       MetaWaylandTransactionEntry *entry;
 
       entry = meta_wayland_transaction_get_entry (transaction, surface);
-      meta_wayland_surface_apply_state (surface, entry->state);
+      states[i] = entry->state;
+      meta_wayland_transaction_apply_subsurface_position (surface, entry);
+      if (entry->state)
+        meta_wayland_surface_apply_state (surface, entry->state);
 
       if (surface->transaction.last_committed == transaction)
         {
@@ -188,7 +209,10 @@ meta_wayland_transaction_apply (MetaWaylandTransaction  *transaction,
 
   /* Synchronize child states from descendants to ancestors */
   for (i = num_surfaces - 1; i >= 0; i--)
-    meta_wayland_transaction_sync_child_states (surfaces[i]);
+    {
+      if (states[i])
+        meta_wayland_transaction_sync_child_states (surfaces[i]);
+    }
 
   meta_wayland_transaction_free (transaction);
 }
@@ -296,6 +320,58 @@ meta_wayland_transaction_add_state (MetaWaylandTransaction  *transaction,
   entry->state = state;
 }
 
+void
+meta_wayland_transaction_add_subsurface_position (MetaWaylandTransaction *transaction,
+                                                  MetaWaylandSurface     *surface)
+{
+  MetaWaylandTransactionEntry *entry;
+
+  entry = meta_wayland_transaction_ensure_entry (transaction, surface);
+  entry->x = surface->sub.pending_x;
+  entry->y = surface->sub.pending_y;
+  entry->has_sub_pos = TRUE;
+  surface->sub.pending_pos = FALSE;
+}
+
+static gboolean
+meta_wayland_transaction_add_cached_state (MetaWaylandTransaction *transaction,
+                                           MetaWaylandSurface     *surface)
+{
+  MetaWaylandSurfaceState *cached = surface->cached_state;
+  gboolean is_synchronized;
+
+  is_synchronized = meta_wayland_surface_is_synchronized (surface);
+
+  if (is_synchronized && cached)
+    {
+      meta_wayland_transaction_add_state (transaction, surface, cached);
+      surface->cached_state = NULL;
+    }
+
+  if (surface->sub.pending_pos)
+    meta_wayland_transaction_add_subsurface_position (transaction, surface);
+
+  return is_synchronized;
+}
+
+void
+meta_wayland_transaction_add_cached_child_states (MetaWaylandTransaction *transaction,
+                                                  MetaWaylandSurface     *surface)
+{
+  MetaWaylandSurface *subsurface_surface;
+
+  META_WAYLAND_SURFACE_FOREACH_SUBSURFACE (surface, subsurface_surface)
+    meta_wayland_transaction_add_cached_states (transaction, subsurface_surface);
+}
+
+void
+meta_wayland_transaction_add_cached_states (MetaWaylandTransaction *transaction,
+                                            MetaWaylandSurface     *surface)
+{
+  if (meta_wayland_transaction_add_cached_state (transaction, surface))
+    meta_wayland_transaction_add_cached_child_states (transaction, surface);
+}
+
 static void
 meta_wayland_transaction_entry_free (MetaWaylandTransactionEntry *entry)
 {

src/wayland/meta-wayland-transaction.h

@@ -28,6 +28,15 @@ void meta_wayland_transaction_add_state (MetaWaylandTransaction  *transaction,
                                          MetaWaylandSurface      *surface,
                                          MetaWaylandSurfaceState *state);
 
+void meta_wayland_transaction_add_subsurface_position (MetaWaylandTransaction *transaction,
+                                                       MetaWaylandSurface     *surface);
+
+void meta_wayland_transaction_add_cached_states (MetaWaylandTransaction *transaction,
+                                                 MetaWaylandSurface     *surface);
+
+void meta_wayland_transaction_add_cached_child_states (MetaWaylandTransaction *transaction,
+                                                       MetaWaylandSurface     *surface);
+
 MetaWaylandTransaction *meta_wayland_transaction_new (MetaWaylandCompositor *compositor);
 
 void meta_wayland_transaction_free (MetaWaylandTransaction *transaction);