remote-desktop/virtual: Drop absolute events if not active

If the remote desktop service emits absolute input events (e.g. absolute
pointer events) before the stream has started streaming, we don't have a
virtual monitor, as the size has not been negotiated yet. When this
happens, just drop the event. Remote desktop services should probably
make sure not to send events before the streaming has started, but them
doing so anyway shouldn't trigger a crash, which would be the case
otherwise.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2270>

src/backends/meta-screen-cast-stream-src.c

@@ -678,7 +678,7 @@ meta_screen_cast_stream_src_maybe_record_frame (MetaScreenCastStreamSrc  *src,
   pw_stream_queue_buffer (priv->pipewire_stream, buffer);
 }
 
-static gboolean
+gboolean
 meta_screen_cast_stream_src_is_enabled (MetaScreenCastStreamSrc *src)
 {
   MetaScreenCastStreamSrcPrivate *priv =

src/backends/meta-screen-cast-stream-src.h

@@ -82,6 +82,8 @@ struct _MetaScreenCastStreamSrcClass
 
 void meta_screen_cast_stream_src_close (MetaScreenCastStreamSrc *src);
 
+gboolean meta_screen_cast_stream_src_is_enabled (MetaScreenCastStreamSrc *src);
+
 void meta_screen_cast_stream_src_maybe_record_frame (MetaScreenCastStreamSrc  *src,
                                                      MetaScreenCastRecordFlag  flags);
 

src/backends/meta-screen-cast-virtual-stream.c

@@ -93,6 +93,9 @@ meta_screen_cast_virtual_stream_transform_position (MetaScreenCastStream *stream
   ClutterStageView *view;
   MetaRectangle view_layout;
 
+  if (!meta_screen_cast_stream_src_is_enabled (src))
+    return FALSE;
+
   view = meta_screen_cast_virtual_stream_src_get_view (virtual_src);
   if (!view)
     return FALSE;