[mutter] cursor-renderer: Disconnect the overlay cursor from the displayed cursor

[Georges Basile Stavracas Neto <gbsneto src gnome org>]

commit 2d010c9b84fbe874bcedea9d23c6dd78353b1a04
Author: Jonas Ådahl <jadahl gmail com>
Date:   Fri Jul 31 21:13:45 2020 +0200

    cursor-renderer: Disconnect the overlay cursor from the displayed cursor
    
    The displayed cursor is the one displayed on the screen, e.g. via the
    hardware cursor plane, by Xorg, or using the stage overlay.
    
    When screen recording under X11, we don't get a stream of pointer and
    cursor updates, as they might be grabbed by some other client. Because
    of this, the cursor tracker or cursor renderer are not kept up to date
    with positional and cursor state.
    
    To be able to use the stage overlays when recording, we need to be able
    to update the overlay without updating the displayed cursor, as we
    shouldn't update the X server with cursor state we just retrieved from
    it.
    
    Thus, to achieve this, create a separate overlay cursor pointer. When
    being a display server, they are always the same, but when using X11,
    during screen recording, the overlay one will be polled at a fixed
    interval to get a somewhat up to date state.
    
    https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1391

 src/backends/meta-cursor-renderer.c | 15 ++++++++++-----
 src/backends/meta-cursor-renderer.h |  3 +++
 2 files changed, 13 insertions(+), 5 deletions(-)
---
diff --git a/src/backends/meta-cursor-renderer.c b/src/backends/meta-cursor-renderer.c
index d3ea5ec216..ac81deff66 100644
--- a/src/backends/meta-cursor-renderer.c
+++ b/src/backends/meta-cursor-renderer.c
@@ -58,6 +58,8 @@ struct _MetaCursorRendererPrivate
   float current_y;
 
   MetaCursorSprite *displayed_cursor;
+  MetaCursorSprite *overlay_cursor;
+
   MetaOverlay *stage_overlay;
   gboolean handled_by_backend;
   gulong after_paint_handler_id;
@@ -123,15 +125,17 @@ align_cursor_position (MetaCursorRenderer *renderer,
   graphene_rect_offset (rect, view_layout.x, view_layout.y);
 }
 
-static void
-update_stage_overlay (MetaCursorRenderer *renderer,
-                      MetaCursorSprite   *cursor_sprite)
+void
+meta_cursor_renderer_update_stage_overlay (MetaCursorRenderer *renderer,
+                                           MetaCursorSprite   *cursor_sprite)
 {
   MetaCursorRendererPrivate *priv = meta_cursor_renderer_get_instance_private (renderer);
   ClutterActor *stage = meta_backend_get_stage (priv->backend);
   CoglTexture *texture;
   graphene_rect_t rect = GRAPHENE_RECT_INIT_ZERO;
 
+  g_set_object (&priv->overlay_cursor, cursor_sprite);
+
   if (cursor_sprite)
     {
       rect = meta_cursor_renderer_calculate_rect (renderer, cursor_sprite);
@@ -239,6 +243,7 @@ meta_cursor_renderer_finalize (GObject *object)
   g_clear_signal_handler (&priv->after_paint_handler_id, stage);
 
   g_clear_object (&priv->displayed_cursor);
+  g_clear_object (&priv->overlay_cursor);
 
   G_OBJECT_CLASS (meta_cursor_renderer_parent_class)->finalize (object);
 }
@@ -345,7 +350,7 @@ meta_cursor_renderer_update_cursor (MetaCursorRenderer *renderer,
   if (handled_by_backend != priv->handled_by_backend)
     priv->handled_by_backend = handled_by_backend;
 
-  update_stage_overlay (renderer, cursor_sprite);
+  meta_cursor_renderer_update_stage_overlay (renderer, cursor_sprite);
 }
 
 MetaCursorRenderer *
@@ -408,7 +413,7 @@ meta_cursor_renderer_get_cursor (MetaCursorRenderer *renderer)
 {
   MetaCursorRendererPrivate *priv = meta_cursor_renderer_get_instance_private (renderer);
 
-  return priv->displayed_cursor;
+  return priv->overlay_cursor;
 }
 
 gboolean
diff --git a/src/backends/meta-cursor-renderer.h b/src/backends/meta-cursor-renderer.h
index 386d029d08..7d89af4874 100644
--- a/src/backends/meta-cursor-renderer.h
+++ b/src/backends/meta-cursor-renderer.h
@@ -84,4 +84,7 @@ graphene_rect_t meta_cursor_renderer_calculate_rect (MetaCursorRenderer *rendere
 void meta_cursor_renderer_emit_painted (MetaCursorRenderer *renderer,
                                         MetaCursorSprite   *cursor_sprite);
 
+void meta_cursor_renderer_update_stage_overlay (MetaCursorRenderer *renderer,
+                                                MetaCursorSprite   *cursor_sprite);
+
 #endif /* META_CURSOR_RENDERER_H */