waylandsink: create/destroy the display when entering/leaving the READY state instead of PAUSED

This is the only way to get the negotiation working with the dynamic
detection of formats from the display, because the pipeline needs
to know the supported formats in the READY state and the supported
formats can only be known if we open the display.

Unfortunately,in wayland we cannot have a separate connection to
the display from the rest of the application, so we need to ask for a
window handle when going to READY in order to get the display from it.

And since it's too early to create a top level window from the state
change to READY, create it in render() when there is no other window.

This also changes set_window_handle() to not support window handle
changes in PAUSED/PLAYING (because it's complex to handle and useless
in practice) and make sure that there is always a valid display pointer
around in the READY state.

ext/wayland/gstwaylandsink.c

@@ -229,9 +229,24 @@ gst_wayland_sink_change_state (GstElement * element, GstStateChange transition)
   GstStateChangeReturn ret = GST_STATE_CHANGE_SUCCESS;
 
   switch (transition) {
-    case GST_STATE_CHANGE_READY_TO_PAUSED:
+    case GST_STATE_CHANGE_NULL_TO_READY:
       if (!sink->window)
         gst_video_overlay_prepare_window_handle (GST_VIDEO_OVERLAY (sink));
+
+      /* if nobody set a window handle, create at least a display */
+      if (!sink->display) {
+        GError *error = NULL;
+
+        sink->display = gst_wl_display_new (sink->display_name, &error);
+
+        if (sink->display == NULL) {
+          GST_ELEMENT_WARNING (sink, RESOURCE, OPEN_READ_WRITE,
+              ("Could not initialise Wayland output"),
+              ("Failed to create GstWlDisplay: '%s'", error->message));
+          g_error_free (error);
+          return GST_STATE_CHANGE_FAILURE;
+        }
+      }
       break;
     default:
       break;
@@ -244,6 +259,12 @@ gst_wayland_sink_change_state (GstElement * element, GstStateChange transition)
   switch (transition) {
     case GST_STATE_CHANGE_PAUSED_TO_READY:
       if (gst_wl_window_is_toplevel (sink->window)) {
+        gst_buffer_replace (&sink->last_buffer, NULL);
+        g_clear_object (&sink->window);
+      }
+      break;
+    case GST_STATE_CHANGE_READY_TO_NULL:
+      if (sink->display && !sink->window) {     /* -> the window was toplevel */
         /* Force all buffers to return to the pool, regardless of
          * whether the compositor has released them or not. We are
          * going to kill the display, so we need to return all buffers
@@ -261,8 +282,6 @@ gst_wayland_sink_change_state (GstElement * element, GstStateChange transition)
           gst_wayland_compositor_release_all_buffers (GST_WAYLAND_BUFFER_POOL
               (sink->pool));
         }
-        gst_buffer_replace (&sink->last_buffer, NULL);
-        g_clear_object (&sink->window);
         g_clear_object (&sink->display);
         g_clear_object (&sink->pool);
       }
@@ -325,7 +344,6 @@ gst_wayland_sink_set_caps (GstBaseSink * bsink, GstCaps * caps)
   GstWaylandSink *sink;
   GstBufferPool *newpool;
   GstVideoInfo info;
-  GError *error = NULL;
   enum wl_shm_format format;
   GArray *formats;
   gint i;
@@ -349,18 +367,6 @@ gst_wayland_sink_set_caps (GstBaseSink * bsink, GstCaps * caps)
   sink->video_width = info.width;
   sink->video_height = info.height;
 
-  /* create the output window if needed */
-  if (!sink->window) {
-    if (!sink->display)
-      sink->display = gst_wl_display_new (sink->display_name, &error);
-
-    if (sink->display == NULL)
-      goto display_failed;
-
-    sink->window = gst_wl_window_new_toplevel (sink->display, sink->video_width,
-        sink->video_height);
-  }
-
   /* verify we support the requested format */
   formats = sink->display->formats;
   for (i = 0; i < formats->len; i++) {
@@ -394,14 +400,6 @@ invalid_format:
         "Could not locate image format from caps %" GST_PTR_FORMAT, caps);
     goto failure;
   }
-display_failed:
-  {
-    GST_ELEMENT_ERROR (sink, RESOURCE, OPEN_READ_WRITE,
-        ("Could not initialise Wayland output"),
-        ("Failed to create GstWlDisplay: '%s'", error->message));
-    g_error_free (error);
-    goto failure;
-  }
 unsupported_format:
   {
     GST_DEBUG_OBJECT (sink, "Format %s is not available on the display",
@@ -574,6 +572,10 @@ gst_wayland_sink_render (GstBaseSink * bsink, GstBuffer * buffer)
 
   GST_LOG_OBJECT (sink, "render buffer %p", buffer);
 
+  if (!sink->window)
+    sink->window = gst_wl_window_new_toplevel (sink->display, sink->video_width,
+        sink->video_height);
+
   /* surface is resizing - drop buffers until finished */
   if (sink->drawing_frozen)
     goto done;
@@ -656,16 +658,15 @@ gst_wayland_sink_set_window_handle (GstVideoOverlay * overlay, guintptr handle)
   GstWaylandSink *sink = GST_WAYLAND_SINK (overlay);
   GstWaylandWindowHandle *whandle = (GstWaylandWindowHandle *) handle;
   GError *error = NULL;
-  GstPad *peer;
 
   g_return_if_fail (sink != NULL);
+  g_return_if_fail (GST_STATE (sink) < GST_STATE_PAUSED);
+
+  GST_OBJECT_LOCK (sink);
 
   GST_DEBUG_OBJECT (sink, "Setting window handle %" GST_PTR_FORMAT,
       (void *) handle);
 
-  if (GST_STATE (sink) > GST_STATE_READY)
-    gst_wayland_sink_pause_rendering (GST_WAYLAND_VIDEO (sink));
-
   g_clear_object (&sink->window);
   g_clear_object (&sink->display);
 
@@ -683,18 +684,21 @@ gst_wayland_sink_set_window_handle (GstVideoOverlay * overlay, guintptr handle)
       sink->window = gst_wl_window_new_from_surface (sink->display,
           whandle->surface, whandle->width, whandle->height);
     }
-  } else {
+  }
-    /* reconfigure to force creation of new window in set_caps */
+
-    sink->negotiated = FALSE;
+  if (!sink->display && GST_STATE (sink) == GST_STATE_READY) {
-    peer = gst_pad_get_peer (GST_VIDEO_SINK_PAD (sink));
+    /* we need a display to be in READY */
-    if (peer) {
+    sink->display = gst_wl_display_new (sink->display_name, &error);
-      gst_pad_send_event (peer, gst_event_new_reconfigure ());
+
-      gst_object_unref (peer);
+    if (sink->display == NULL) {
+      GST_ELEMENT_ERROR (sink, RESOURCE, OPEN_READ_WRITE,
+          ("Could not initialise Wayland output"),
+          ("Failed to create GstWlDisplay: '%s'", error->message));
+      g_error_free (error);
     }
   }
 
-  if (GST_STATE (sink) > GST_STATE_READY)
+  GST_OBJECT_UNLOCK (sink);
-    gst_wayland_sink_resume_rendering (GST_WAYLAND_VIDEO (sink));
 }
 
 static void