cogl-gst: add cogl_gst_video_sink_get_natural_size() api

This adds api for querying a "natural" width and height for a video
which has the correct aspect ratio for displaying on square, 1:1 pixels.

The natural size is the minimum size where downscaling is not required.

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

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

@@ -1658,6 +1658,54 @@ cogl_gst_video_sink_fit_size (CoglGstVideoSink *vt,
     }
 }
 
+void
+cogl_gst_video_sink_get_natural_size (CoglGstVideoSink *vt,
+                                      float *width,
+                                      float *height)
+{
+  GstVideoInfo *info;
+
+  g_return_val_if_fail (COGL_GST_IS_VIDEO_SINK (vt), 0.);
+
+  info = &vt->priv->info;
+
+  if (info->par_n > info->par_d)
+    {
+      /* To display the video at the right aspect ratio then in this
+       * case the pixels need to be stretched horizontally and so we
+       * use the unscaled height as our reference.
+       */
+
+      if (height)
+        *height = info->height;
+      if (width)
+        *width = cogl_gst_video_sink_get_width_for_height (vt, info->height);
+    }
+  else
+    {
+      if (width)
+        *width = info->width;
+      if (height)
+        *height = cogl_gst_video_sink_get_height_for_width (vt, info->width);
+    }
+}
+
+float
+cogl_gst_video_sink_get_natural_width (CoglGstVideoSink *vt)
+{
+  float width;
+  cogl_gst_video_sink_get_natural_size (vt, &width, NULL);
+  return width;
+}
+
+float
+cogl_gst_video_sink_get_natural_height (CoglGstVideoSink *vt)
+{
+  float height;
+  cogl_gst_video_sink_get_natural_size (vt, NULL, &height);
+  return height;
+}
+
 CoglBool
 cogl_gst_video_sink_is_ready (CoglGstVideoSink *sink)
 {

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

@@ -412,6 +412,77 @@ float
 cogl_gst_video_sink_get_height_for_width (CoglGstVideoSink *sink,
                                           float width);
 
+/**
+ * cogl_gst_video_sink_get_natural_size:
+ * @sink: A #CoglGstVideoSink
+ * @width: (out): return location for the video's natural width
+ * @height: (out): return location for the video's natural height
+ *
+ * Considering the real resolution of the video as well as the aspect
+ * ratio of pixel data that may need to be stretched when being displayed;
+ * this function calculates what the natural size of the underlying
+ * video source is.
+ *
+ * The natural size has the correct aspect ratio for displaying the
+ * video and is the minimum size where downscaling is not required.
+ *
+ * <note>This natural size is calculated assuming that the video will
+ * be displayed on square pixels.</note>
+ *
+ * Since: 1.18
+ * Stability: unstable
+ */
+void
+cogl_gst_video_sink_get_natural_size (CoglGstVideoSink *sink,
+                                      float *width,
+                                      float *height);
+
+/**
+ * cogl_gst_video_sink_get_natural_width:
+ * @sink: A #CoglGstVideoSink
+ *
+ * Considering the real resolution of the video as well as the aspect
+ * ratio of pixel data that may need to be stretched when being displayed;
+ * this function calculates what the natural size of the underlying
+ * video source is, and returns its width.
+ *
+ * The natural size has the correct aspect ratio for displaying the
+ * video and is the minimum size where downscaling is not required.
+ *
+ * <note>This natural size is calculated assuming that the video will
+ * be displayed on square pixels.</note>
+ *
+ * Return value: The video's natural width
+ *
+ * Since: 1.18
+ * Stability: unstable
+ */
+float
+cogl_gst_video_sink_get_natural_width (CoglGstVideoSink *sink);
+
+/**
+ * cogl_gst_video_sink_get_natural_height:
+ * @sink: A #CoglGstVideoSink
+ *
+ * Considering the real resolution of the video as well as the aspect
+ * ratio of pixel data that may need to be stretched when being displayed;
+ * this function calculates what the natural size of the underlying
+ * video source is, and returns its height.
+ *
+ * The natural size has the correct aspect ratio for displaying the
+ * video and is the minimum size where downscaling is not required.
+ *
+ * <note>This natural size is calculated assuming that the video will
+ * be displayed on square pixels.</note>
+ *
+ * Return value: The video's natural height
+ *
+ * Since: 1.18
+ * Stability: unstable
+ */
+float
+cogl_gst_video_sink_get_natural_height (CoglGstVideoSink *sink);
+
 /**
  * CoglGstRectangle:
  * @x: The X coordinate of the top left of the rectangle