cursor-renderer: Always keep the cursor overlay on the stage

Only when the cursor isn't handled by the backend is the overlay made
visible. This is intended to be used when painting the stage to an
offscreen using clutter_stage_paint_to_(frame)buffer() in a way where
the cursor is always included.

https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1391

src/backends/meta-cursor-renderer.c

@@ -124,8 +124,8 @@ align_cursor_position (MetaCursorRenderer *renderer,
 }
 
 static void
-queue_redraw (MetaCursorRenderer *renderer,
+update_stage_overlay (MetaCursorRenderer *renderer,
-              MetaCursorSprite   *cursor_sprite)
+                      MetaCursorSprite   *cursor_sprite)
 {
   MetaCursorRendererPrivate *priv = meta_cursor_renderer_get_instance_private (renderer);
   ClutterActor *stage = meta_backend_get_stage (priv->backend);
@@ -145,11 +145,12 @@ queue_redraw (MetaCursorRenderer *renderer,
   if (!priv->stage_overlay)
     priv->stage_overlay = meta_stage_create_cursor_overlay (META_STAGE (stage));
 
-  if (cursor_sprite && !priv->handled_by_backend)
+  if (cursor_sprite)
     texture = meta_cursor_sprite_get_cogl_texture (cursor_sprite);
   else
     texture = NULL;
 
+  meta_overlay_set_visible (priv->stage_overlay, !priv->handled_by_backend);
   meta_stage_update_cursor_overlay (META_STAGE (stage), priv->stage_overlay,
                                     texture, &rect);
 }
@@ -334,7 +335,6 @@ meta_cursor_renderer_update_cursor (MetaCursorRenderer *renderer,
 {
   MetaCursorRendererPrivate *priv = meta_cursor_renderer_get_instance_private (renderer);
   gboolean handled_by_backend;
-  gboolean should_redraw = FALSE;
 
   if (cursor_sprite)
     meta_cursor_sprite_prepare_at (cursor_sprite,
@@ -345,16 +345,9 @@ meta_cursor_renderer_update_cursor (MetaCursorRenderer *renderer,
     META_CURSOR_RENDERER_GET_CLASS (renderer)->update_cursor (renderer,
                                                               cursor_sprite);
   if (handled_by_backend != priv->handled_by_backend)
-    {
+    priv->handled_by_backend = handled_by_backend;
-      priv->handled_by_backend = handled_by_backend;
-      should_redraw = TRUE;
-    }
 
-  if (!handled_by_backend)
+  update_stage_overlay (renderer, cursor_sprite);
-    should_redraw = TRUE;
-
-  if (should_redraw)
-    queue_redraw (renderer, cursor_sprite);
 }
 
 MetaCursorRenderer *

src/backends/meta-stage-private.h

@@ -54,6 +54,11 @@ void              meta_stage_update_cursor_overlay   (MetaStage       *stage,
                                                       CoglTexture     *texture,
                                                       graphene_rect_t *rect);
 
+void meta_overlay_set_visible (MetaOverlay *overlay,
+                               gboolean     is_visible);
+
+gboolean meta_overlay_is_visible (MetaOverlay *overlay);
+
 void meta_stage_set_active (MetaStage *stage,
                             gboolean   is_active);
 

src/backends/meta-stage.c

@@ -50,7 +50,9 @@ struct _MetaStageWatch
 
 struct _MetaOverlay
 {
-  gboolean enabled;
+  MetaStage *stage;
+
+  gboolean is_visible;
 
   CoglPipeline *pipeline;
   CoglTexture *texture;
@@ -75,12 +77,15 @@ struct _MetaStage
 G_DEFINE_TYPE (MetaStage, meta_stage, CLUTTER_TYPE_STAGE);
 
 static MetaOverlay *
-meta_overlay_new (void)
+meta_overlay_new (MetaStage *stage)
 {
+  ClutterBackend *clutter_backend =
+    meta_backend_get_clutter_backend (stage->backend);
+  CoglContext *ctx = clutter_backend_get_cogl_context (clutter_backend);
   MetaOverlay *overlay;
-  CoglContext *ctx = clutter_backend_get_cogl_context (clutter_get_default_backend ());
 
   overlay = g_slice_new0 (MetaOverlay);
+  overlay->stage = stage;
   overlay->pipeline = cogl_pipeline_new (ctx);
 
   return overlay;
@@ -105,15 +110,9 @@ meta_overlay_set (MetaOverlay     *overlay,
       overlay->texture = texture;
 
       if (texture)
-        {
+        cogl_pipeline_set_layer_texture (overlay->pipeline, 0, texture);
-          cogl_pipeline_set_layer_texture (overlay->pipeline, 0, texture);
-          overlay->enabled = TRUE;
-        }
       else
-        {
+        cogl_pipeline_set_layer_texture (overlay->pipeline, 0, NULL);
-          cogl_pipeline_set_layer_texture (overlay->pipeline, 0, NULL);
-          overlay->enabled = FALSE;
-        }
     }
 
   overlay->current_rect = *rect;
@@ -125,10 +124,11 @@ meta_overlay_paint (MetaOverlay         *overlay,
 {
   CoglFramebuffer *framebuffer;
 
-  if (!overlay->enabled)
+  if (!overlay->texture)
     return;
 
-  g_assert (meta_is_wayland_compositor ());
+  if (!overlay->is_visible)
+    return;
 
   framebuffer = clutter_paint_context_get_framebuffer (paint_context);
   cogl_framebuffer_draw_rectangle (framebuffer,
@@ -345,7 +345,7 @@ queue_redraw_for_overlay (MetaStage   *stage,
     }
 
   /* Draw the overlay at the new position */
-  if (overlay->enabled)
+  if (overlay->is_visible && overlay->texture)
     queue_redraw_clutter_rect (stage, overlay, &overlay->current_rect);
 }
 
@@ -354,7 +354,7 @@ meta_stage_create_cursor_overlay (MetaStage *stage)
 {
   MetaOverlay *overlay;
 
-  overlay = meta_overlay_new ();
+  overlay = meta_overlay_new (stage);
   stage->overlays = g_list_prepend (stage->overlays, overlay);
 
   return overlay;
@@ -380,12 +380,27 @@ meta_stage_update_cursor_overlay (MetaStage       *stage,
                                   CoglTexture     *texture,
                                   graphene_rect_t *rect)
 {
-  g_assert (meta_is_wayland_compositor () || texture == NULL);
-
   meta_overlay_set (overlay, texture, rect);
   queue_redraw_for_overlay (stage, overlay);
 }
 
+void
+meta_overlay_set_visible (MetaOverlay *overlay,
+                          gboolean     is_visible)
+{
+  if (overlay->is_visible == is_visible)
+    return;
+
+  overlay->is_visible = is_visible;
+  queue_redraw_for_overlay (overlay->stage, overlay);
+}
+
+gboolean
+meta_overlay_is_visible (MetaOverlay *overlay)
+{
+  return overlay->is_visible;
+}
+
 void
 meta_stage_set_active (MetaStage *stage,
                        gboolean   is_active)

src/backends/x11/meta-cursor-renderer-x11.c

@@ -90,7 +90,7 @@ meta_cursor_renderer_x11_update_cursor (MetaCursorRenderer *renderer,
       priv->server_cursor_visible = has_server_cursor;
     }
 
-  if (!priv->server_cursor_visible && cursor_sprite)
+  if (cursor_sprite)
     meta_cursor_sprite_realize_texture (cursor_sprite);
 
   return priv->server_cursor_visible;