waylandsink: remove the manual synchronization from pause/resume_rendering and use subsurface sync/desync

Previously, in order to change the surface size we had to let the pipeline
redraw it, which at first also involved re-negotiating caps, etc, so a
synchronization with the pipeline was absolutely necessary.

At the moment, we are using wl_viewport, which separates the surface size
from the buffer size and it also allows us to commit a surface resize without
attaching a new buffer, so it is enough to just do:

gst_wayland_video_pause_rendering():
	wl_subsurface_set_sync()
gst_video_overlay_set_render_rectangle():
	wl_subsurface_set_position()
	wl_viewport_set_destination()
	wl_surface_damage()
	wl_surface_commit()
... commit the parent surface ...
gst_wayland_video_resume_rendering():
	wl_subsurface_set_desync()

This is enough to synchronize a surface resize and the pipeline can continue
drawing independently. Now of course, the names pause/resume_rendering are
bad. I will rename them in another commit.

ext/wayland/gstwaylandsink.c

@@ -164,7 +164,6 @@ gst_wayland_sink_init (GstWaylandSink * sink)
 {
   g_mutex_init (&sink->display_lock);
   g_mutex_init (&sink->render_lock);
-  g_cond_init (&sink->render_cond);
 }
 
 static void
@@ -230,7 +229,6 @@ gst_wayland_sink_finalize (GObject * object)
 
   g_mutex_clear (&sink->display_lock);
   g_mutex_clear (&sink->render_lock);
-  g_cond_clear (&sink->render_cond);
 
   G_OBJECT_CLASS (parent_class)->finalize (object);
 }
@@ -665,10 +663,6 @@ gst_wayland_sink_render (GstBaseSink * bsink, GstBuffer * buffer)
 
   GST_LOG_OBJECT (sink, "render buffer %p", buffer);
 
-  /* surface is resizing - drop buffers until finished */
-  if (sink->drawing_frozen)
-    goto done;
-
   /* drop buffers until we get a frame callback */
   if (g_atomic_int_get (&sink->redraw_pending) == TRUE)
     goto done;
@@ -711,10 +705,6 @@ gst_wayland_sink_render (GstBaseSink * bsink, GstBuffer * buffer)
   gst_buffer_replace (&sink->last_buffer, to_render);
   render_last_buffer (sink);
 
-  /* notify _resume_rendering() in case it's waiting */
-  sink->rendered = TRUE;
-  g_cond_broadcast (&sink->render_cond);
-
   if (buffer != to_render)
     gst_buffer_unref (to_render);
   goto done;
@@ -851,7 +841,13 @@ gst_wayland_sink_pause_rendering (GstWaylandVideo * video)
   g_return_if_fail (sink != NULL);
 
   g_mutex_lock (&sink->render_lock);
-  sink->drawing_frozen = TRUE;
+  if (!sink->window || !sink->window->subsurface) {
+    g_mutex_unlock (&sink->render_lock);
+    GST_INFO_OBJECT (sink, "pause_rendering called without window, ignoring");
+    return;
+  }
+
+  wl_subsurface_set_sync (sink->window->subsurface);
   g_mutex_unlock (&sink->render_lock);
 }
 
@@ -864,19 +860,13 @@ gst_wayland_sink_resume_rendering (GstWaylandVideo * video)
   GST_DEBUG_OBJECT (sink, "resuming rendering");
 
   g_mutex_lock (&sink->render_lock);
-  sink->drawing_frozen = FALSE;
+  if (!sink->window || !sink->window->subsurface) {
-
+    g_mutex_unlock (&sink->render_lock);
-  if (GST_STATE (sink) == GST_STATE_PLAYING) {
+    GST_INFO_OBJECT (sink, "resume_rendering called without window, ignoring");
-    sink->rendered = FALSE;
+    return;
-    while (sink->rendered == FALSE)
-      g_cond_wait (&sink->render_cond, &sink->render_lock);
-    GST_DEBUG_OBJECT (sink, "synchronized with render()");
-  } else if (sink->window && sink->last_buffer &&
-      g_atomic_int_get (&sink->redraw_pending) == FALSE) {
-    render_last_buffer (sink);
-    GST_DEBUG_OBJECT (sink, "last buffer redrawn");
   }
 
+  wl_subsurface_set_desync (sink->window->subsurface);
   g_mutex_unlock (&sink->render_lock);
 }
 

ext/wayland/gstwaylandsink.h

@@ -63,10 +63,7 @@ struct _GstWaylandSink
   gchar *display_name;
 
   gboolean redraw_pending;
-  gboolean drawing_frozen;
-  gboolean rendered;
   GMutex render_lock;
-  GCond render_cond;
   GstBuffer *last_buffer;
 };