cogl-gst: adds _sink_is_ready() api

This adds a cogl_gst_video_sink_is_ready() for code to be able to
check if it's safe to call cogl_gst_video_sink_get_pipeline() or
cogl_gst_video_sink_setup_pipeline() without causing an error.
Normally an application can listen for the pipeline-ready signal but
sometimes a sink can be passed between components that didn't have an
opportunity to connect a signal handler, so they need a way to
directly check the status.

Reviewed-by: Neil Roberts <neil@linux.intel.com>

(cherry picked from commit 9e7db391a87beee7c448f2a67b3e7202779ce9b2)

cogl-gst/cogl-gst-video-sink.c

@@ -1352,3 +1352,9 @@ cogl_gst_video_sink_fit_size (CoglGstVideoSink *vt,
         }
     }
 }
+
+CoglBool
+cogl_gst_video_sink_is_ready (CoglGstVideoSink *sink)
+{
+  return !!sink->priv->renderer;
+}

cogl-gst/cogl-gst-video-sink.h

@@ -191,6 +191,26 @@ cogl_gst_video_sink_get_type (void) G_GNUC_CONST;
 CoglGstVideoSink *
 cogl_gst_video_sink_new (CoglContext *ctx);
 
+/**
+ * cogl_gst_video_sink_is_ready:
+ * @sink: The #CoglGstVideoSink
+ *
+ * Returns whether the pipeline is ready and so
+ * cogl_gst_video_sink_get_pipeline() and
+ * cogl_gst_video_sink_setup_pipeline() can be called without causing error.
+ *
+ * Note: Normally an application will wait until the
+ * #CoglGstVideoSink::pipeline-ready signal is emitted instead of
+ * polling the ready status with this api, but sometimes when a sink
+ * is passed between components that didn't have an opportunity to
+ * connect a signal handler this can be useful.
+ *
+ * Return value: %TRUE if the sink is ready, else %FALSE
+ * Since: 1.16
+ */
+CoglBool
+cogl_gst_video_sink_is_ready (CoglGstVideoSink *sink);
+
 /**
  * cogl_gst_video_sink_get_pipeline:
  * @vt: The #CoglGstVideoSink

doc/reference/cogl-gst/cogl-gst-sections.txt

@@ -13,6 +13,7 @@ cogl_gst_video_sink_setup_pipeline
 cogl_gst_video_sink_get_free_layer
 cogl_gst_video_sink_set_first_layer
 cogl_gst_video_sink_set_default_sample
+cogl_gst_video_sink_is_ready
 cogl_gst_video_sink_get_aspect
 cogl_gst_video_sink_get_width_for_height
 cogl_gst_video_sink_get_height_for_width