waylandsink: Keep per display wayland buffer caches

Instead of attaching a single wayland wl_buffer to each GStBuffer as qdata,
keep a separate cache for each display.
A unique wl_buffer and associated metadata is created for each display.
This allows for sharing of GstBuffer objects between multiple
displays, such as when using tee elements.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-bad/-/merge_requests/1401>

ext/wayland/gstwaylandsink.c

@@ -655,7 +655,7 @@ render_last_buffer (GstWaylandSink * sink, gboolean redraw)
   struct wl_surface *surface;
   struct wl_callback *callback;
 
-  wlbuffer = gst_buffer_get_wl_buffer (sink->last_buffer);
+  wlbuffer = gst_buffer_get_wl_buffer (sink->display, sink->last_buffer);
   surface = gst_wl_window_get_wl_surface (sink->window);
 
   sink->redraw_pending = TRUE;
@@ -723,7 +723,7 @@ gst_wayland_sink_show_frame (GstVideoSink * vsink, GstBuffer * buffer)
   if (G_UNLIKELY (sink->window->render_rectangle.w == 0))
     goto no_window_size;
 
-  wlbuffer = gst_buffer_get_wl_buffer (buffer);
+  wlbuffer = gst_buffer_get_wl_buffer (sink->display, buffer);
 
   if (G_LIKELY (wlbuffer && wlbuffer->display == sink->display)) {
     GST_LOG_OBJECT (sink, "buffer %p has a wl_buffer from our display, "
@@ -807,7 +807,7 @@ gst_wayland_sink_show_frame (GstVideoSink * vsink, GstBuffer * buffer)
       if (ret != GST_FLOW_OK)
         goto no_buffer;
 
-      wlbuffer = gst_buffer_get_wl_buffer (to_render);
+      wlbuffer = gst_buffer_get_wl_buffer (sink->display, to_render);
 
       /* attach a wl_buffer if there isn't one yet */
       if (G_UNLIKELY (!wlbuffer)) {

ext/wayland/wlbuffer.c

@@ -38,7 +38,7 @@
  *   -----------------     -------------     ---------------
  *
  * A GstBufferPool normally holds references to its GstBuffers and each buffer
- * holds a reference to a GstWlBuffer (saved in the GstMiniObject qdata).
+ * holds a reference to a GstWlBuffer (saved in the GstMiniObject weak ref data).
  * When a GstBuffer is in use, it holds a reference back to the pool and the
  * pool doesn't hold a reference to the GstBuffer. When the GstBuffer is unrefed
  * externally, it returns back to the pool and the pool holds again a reference
@@ -83,8 +83,6 @@ GST_DEBUG_CATEGORY_EXTERN (gstwayland_debug);
 
 G_DEFINE_TYPE (GstWlBuffer, gst_wl_buffer, G_TYPE_OBJECT);
 
-static G_DEFINE_QUARK (GstWlBufferQDataQuark, gst_wl_buffer_qdata);
-
 static void
 gst_wl_buffer_dispose (GObject * gobject)
 {
@@ -97,7 +95,7 @@ gst_wl_buffer_dispose (GObject * gobject)
    * block and in the end the display will increase the refcount
    * of this GstWlBuffer, so it will not be finalized */
   if (self->display)
-    gst_wl_display_unregister_buffer (self->display, self);
+    gst_wl_display_unregister_buffer (self->display, self->gstbuffer);
 
   G_OBJECT_CLASS (gst_wl_buffer_parent_class)->dispose (gobject);
 }
@@ -150,7 +148,6 @@ static void
 gstbuffer_disposed (GstWlBuffer * self)
 {
   g_assert (!self->used_by_compositor);
-  self->gstbuffer = NULL;
 
   GST_TRACE_OBJECT (self, "owning GstBuffer was finalized");
 
@@ -170,25 +167,25 @@ gst_buffer_add_wl_buffer (GstBuffer * gstbuffer, struct wl_buffer *wlbuffer,
   self->wlbuffer = wlbuffer;
   self->display = display;
 
-  gst_wl_display_register_buffer (self->display, self);
+  gst_wl_display_register_buffer (self->display, self->gstbuffer, self);
 
   wl_buffer_add_listener (self->wlbuffer, &buffer_listener, self);
 
-  gst_mini_object_set_qdata ((GstMiniObject *) gstbuffer,
-      gst_wl_buffer_qdata_quark (), self, (GDestroyNotify) gstbuffer_disposed);
+  gst_mini_object_weak_ref (GST_MINI_OBJECT (gstbuffer),
+      (GstMiniObjectNotify) gstbuffer_disposed, self);
+
 
   return self;
 }
 
 GstWlBuffer *
-gst_buffer_get_wl_buffer (GstBuffer * gstbuffer)
+gst_buffer_get_wl_buffer (GstWlDisplay * display, GstBuffer * gstbuffer)
 {
-  return gst_mini_object_get_qdata ((GstMiniObject *) gstbuffer,
-      gst_wl_buffer_qdata_quark ());
+  return gst_wl_display_lookup_buffer (display, gstbuffer);
 }
 
 void
-gst_wl_buffer_force_release_and_unref (GstWlBuffer * self)
+gst_wl_buffer_force_release_and_unref (GstBuffer * buf, GstWlBuffer * self)
 {
   /* Force a buffer release.
    * At this point, the GstWlDisplay has killed its event loop,
@@ -212,6 +209,7 @@ gst_wl_buffer_force_release_and_unref (GstWlBuffer * self)
   wl_buffer_destroy (self->wlbuffer);
   self->wlbuffer = NULL;
   self->display = NULL;
+  self->gstbuffer = NULL;
 
   /* remove the reference that the caller (GstWlDisplay) owns */
   g_object_unref (self);

ext/wayland/wlbuffer.h

@@ -56,9 +56,9 @@ GType gst_wl_buffer_get_type (void);
 
 GstWlBuffer * gst_buffer_add_wl_buffer (GstBuffer * gstbuffer,
     struct wl_buffer * wlbuffer, GstWlDisplay * display);
-GstWlBuffer * gst_buffer_get_wl_buffer (GstBuffer * gstbuffer);
+GstWlBuffer * gst_buffer_get_wl_buffer (GstWlDisplay * display, GstBuffer * gstbuffer);
 
-void gst_wl_buffer_force_release_and_unref (GstWlBuffer * self);
+void gst_wl_buffer_force_release_and_unref (GstBuffer *buf, GstWlBuffer * self);
 
 void gst_wl_buffer_attach (GstWlBuffer * self, struct wl_surface *surface);
 

ext/wayland/wldisplay.c

@@ -52,6 +52,12 @@ gst_wl_display_init (GstWlDisplay * self)
   g_mutex_init (&self->buffers_mutex);
 }
 
+static void
+gst_wl_ref_wl_buffer (gpointer key, gpointer value, gpointer user_data)
+{
+  g_object_ref (value);
+}
+
 static void
 gst_wl_display_finalize (GObject * gobject)
 {
@@ -65,7 +71,7 @@ gst_wl_display_finalize (GObject * gobject)
    * at the same time, take their ownership */
   g_mutex_lock (&self->buffers_mutex);
   self->shutting_down = TRUE;
-  g_hash_table_foreach (self->buffers, (GHFunc) g_object_ref, NULL);
+  g_hash_table_foreach (self->buffers, gst_wl_ref_wl_buffer, NULL);
   g_mutex_unlock (&self->buffers_mutex);
 
   g_hash_table_foreach (self->buffers,
@@ -379,24 +385,36 @@ gst_wl_display_new_existing (struct wl_display * display,
 }
 
 void
-gst_wl_display_register_buffer (GstWlDisplay * self, gpointer buf)
+gst_wl_display_register_buffer (GstWlDisplay * self, gpointer gstbuffer,
+    gpointer wlbuffer)
 {
   g_assert (!self->shutting_down);
 
-  GST_TRACE_OBJECT (self, "registering GstWlBuffer %p", buf);
+  GST_TRACE_OBJECT (self, "registering GstWlBuffer %p to GstBuffer %p",
+      wlbuffer, gstbuffer);
 
   g_mutex_lock (&self->buffers_mutex);
-  g_hash_table_add (self->buffers, buf);
+  g_hash_table_replace (self->buffers, gstbuffer, wlbuffer);
   g_mutex_unlock (&self->buffers_mutex);
 }
 
+gpointer
+gst_wl_display_lookup_buffer (GstWlDisplay * self, gpointer gstbuffer)
+{
+  gpointer wlbuffer;
+  g_mutex_lock (&self->buffers_mutex);
+  wlbuffer = g_hash_table_lookup (self->buffers, gstbuffer);
+  g_mutex_unlock (&self->buffers_mutex);
+  return wlbuffer;
+}
+
 void
-gst_wl_display_unregister_buffer (GstWlDisplay * self, gpointer buf)
+gst_wl_display_unregister_buffer (GstWlDisplay * self, gpointer gstbuffer)
 {
-  GST_TRACE_OBJECT (self, "unregistering GstWlBuffer %p", buf);
+  GST_TRACE_OBJECT (self, "unregistering GstWlBuffer owned by %p", gstbuffer);
 
   g_mutex_lock (&self->buffers_mutex);
   if (G_LIKELY (!self->shutting_down))
-    g_hash_table_remove (self->buffers, buf);
+    g_hash_table_remove (self->buffers, gstbuffer);
   g_mutex_unlock (&self->buffers_mutex);
 }

ext/wayland/wldisplay.h

@@ -85,8 +85,10 @@ GstWlDisplay *gst_wl_display_new_existing (struct wl_display * display,
     gboolean take_ownership, GError ** error);
 
 /* see wlbuffer.c for explanation */
-void gst_wl_display_register_buffer (GstWlDisplay * self, gpointer buf);
-void gst_wl_display_unregister_buffer (GstWlDisplay * self, gpointer buf);
+void gst_wl_display_register_buffer (GstWlDisplay * self, gpointer gstbuffer,
+    gpointer wlbuffer);
+void gst_wl_display_unregister_buffer (GstWlDisplay * self, gpointer gstbuffer);
+gpointer gst_wl_display_lookup_buffer (GstWlDisplay * self, gpointer gstbuffer);
 
 gboolean gst_wl_display_check_format_for_shm (GstWlDisplay * display,
     GstVideoFormat format);