[mutter] screen-cast-monitor-stream-src: Only send cursor bitmap when it changes

[Jonas Ådahl <jadahl src gnome org>]

commit 56d260cfb3f6a7b4d20aa73ce08da007883d9b7c
Author: Jonas Ådahl <jadahl gmail com>
Date:   Thu Jan 3 16:51:08 2019 +0100

    screen-cast-monitor-stream-src: Only send cursor bitmap when it changes
    
    To avoid unnecessary pixel copying, only send the cursor bitmap when it
    changes. This also allows the receiver to know when the cursor bitmap
    actually changed.
    
    https://gitlab.gnome.org/GNOME/mutter/merge_requests/357

 src/backends/meta-screen-cast-monitor-stream-src.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)
---
diff --git a/src/backends/meta-screen-cast-monitor-stream-src.c 
b/src/backends/meta-screen-cast-monitor-stream-src.c
index 50ed6c519..897b86ae6 100644
--- a/src/backends/meta-screen-cast-monitor-stream-src.c
+++ b/src/backends/meta-screen-cast-monitor-stream-src.c
@@ -40,6 +40,8 @@ struct _MetaScreenCastMonitorStreamSrc
 {
   MetaScreenCastStreamSrc parent;
 
+  gboolean cursor_bitmap_invalid;
+
   gulong actors_painted_handler_id;
   gulong paint_handler_id;
   gulong cursor_moved_handler_id;
@@ -194,6 +196,7 @@ static void
 cursor_changed (MetaCursorTracker              *cursor_tracker,
                 MetaScreenCastMonitorStreamSrc *monitor_src)
 {
+  monitor_src->cursor_bitmap_invalid = TRUE;
   sync_cursor_state (monitor_src);
 }
 
@@ -452,6 +455,16 @@ meta_screen_cast_monitor_stream_src_set_cursor_metadata (MetaScreenCastStreamSrc
   spa_meta_cursor->id = 1;
   spa_meta_cursor->position.x = (int32_t) roundf (cursor_position.x);
   spa_meta_cursor->position.y = (int32_t) roundf (cursor_position.y);
+
+  if (!monitor_src->cursor_bitmap_invalid)
+    {
+      spa_meta_cursor->hotspot.x = 0;
+      spa_meta_cursor->hotspot.y = 0;
+      spa_meta_cursor->bitmap_offset = 0;
+      return;
+    }
+  monitor_src->cursor_bitmap_invalid = FALSE;
+
   spa_meta_cursor->bitmap_offset = sizeof (struct spa_meta_cursor);
 
   spa_meta_bitmap = SPA_MEMBER (spa_meta_cursor,
@@ -551,6 +564,7 @@ meta_screen_cast_monitor_stream_src_new (MetaScreenCastMonitorStream  *monitor_s
 static void
 meta_screen_cast_monitor_stream_src_init (MetaScreenCastMonitorStreamSrc *monitor_src)
 {
+  monitor_src->cursor_bitmap_invalid = TRUE;
 }
 
 static void