video-overlay: Add helpers for render-rectangle property

This is a set of helper that makes it easy to enable the render
rectangle to be controllable through a property.

https://bugzilla.gnome.org/show_bug.cgi?id=792798

gst-libs/gst/video/videooverlay.c

@@ -291,6 +291,11 @@
 
 #include "videooverlay.h"
 
+enum
+{
+  PROP_RENDER_RECTANGLE,
+};
+
 GST_DEBUG_CATEGORY_STATIC (gst_video_overlay_debug);
 #define GST_CAT_DEFAULT gst_video_overlay_debug
 
@@ -508,3 +513,88 @@ gst_is_video_overlay_prepare_window_handle_message (GstMessage * msg)
 
   return gst_message_has_name (msg, "prepare-window-handle");
 }
+
+
+/**
+ * gst_video_overlay_install_properties:
+ * @oclass: The class on which the properties will be installed
+ * @last_prop_id: The first free property ID to use
+ *
+ * This helper shall be used by classes implementing the #GstVideoOverlay
+ * interface that want the render rectangle to be controllable using
+ * properties. This helper will install "render-rectangle" property into the
+ * class.
+ *
+ * Since 1.14
+ */
+void
+gst_video_overlay_install_properties (GObjectClass * oclass, gint last_prop_id)
+{
+  g_object_class_install_property (oclass, last_prop_id + PROP_RENDER_RECTANGLE,
+      gst_param_spec_array ("render-rectangle", "Render Rectangle",
+          "The render rectangle ('<x, y, width, height>')",
+          g_param_spec_int ("rect-value", "Rectangle Value",
+              "One of x, y, width or height value.", -1, G_MAXINT, -1,
+              G_PARAM_WRITABLE | G_PARAM_STATIC_STRINGS),
+          G_PARAM_WRITABLE | G_PARAM_STATIC_STRINGS));
+}
+
+/**
+ * gst_video_overlay_set_property:
+ * @object: The instance on which the property is set
+ * @last_prop_id: The highest property ID.
+ * @property_id: The property ID
+ * @value: The #GValue to be set
+ *
+ * This helper shall be used by classes implementing the #GstVideoOverlay
+ * interface that want the render rectangle to be controllable using
+ * properties. This helper will parse and set the render rectangle calling
+ * gst_video_overlay_set_render_rectangle().
+ *
+ * Returns: %TRUE if the @property_id matches the GstVideoOverlay property
+ *
+ * Since 1.14
+ */
+gboolean
+gst_video_overlay_set_property (GObject * object, gint last_prop_id,
+    guint property_id, const GValue * value)
+{
+  gboolean ret = FALSE;
+
+  if (property_id == last_prop_id) {
+    const GValue *v;
+    gint rect[4], i;
+
+    ret = TRUE;
+
+    if (gst_value_array_get_size (value) != 4)
+      goto wrong_format;
+
+    for (i = 0; i < 4; i++) {
+      v = gst_value_array_get_value (value, i);
+      if (!G_VALUE_HOLDS_INT (v))
+        goto wrong_format;
+
+      rect[i] = g_value_get_int (v);
+    }
+
+    gst_video_overlay_set_render_rectangle (GST_VIDEO_OVERLAY (object),
+        rect[0], rect[1], rect[2], rect[3]);
+  }
+
+  return ret;
+
+wrong_format:
+  {
+    GValue string = G_VALUE_INIT;
+
+    g_value_init (&string, G_TYPE_STRING);
+    g_value_transform (value, &string);
+
+    g_critical ("Badly formated rectangle, must contains four gint (got '%s')",
+        g_value_get_string (&string));
+
+    g_value_unset (&string);
+    return TRUE;
+  }
+}

gst-libs/gst/video/videooverlay.h

@@ -23,6 +23,7 @@
 #define __GST_VIDEO_OVERLAY_H__
 
 #include <gst/gst.h>
+#include <gst/video/gstvideosink.h>
 
 G_BEGIN_DECLS
 
@@ -42,6 +43,7 @@ G_BEGIN_DECLS
  */
 typedef struct _GstVideoOverlay GstVideoOverlay;
 typedef struct _GstVideoOverlayInterface GstVideoOverlayInterface;
+typedef struct _GstVideoOverlayProperties GstVideoOverlayProperties;
 
 /**
  * GstVideoOverlayInterface:
@@ -50,6 +52,8 @@ typedef struct _GstVideoOverlayInterface GstVideoOverlayInterface;
  * @handle_events: virtual method to handle events
  * @set_render_rectangle: virtual method to set the render rectangle
  * @set_window_handle: virtual method to configure the window handle
+ * @properties_offset: Offset to the #GstVideoOverlayProperties in the
+ *                     instance allocation. Since 1.14
  *
  * #GstVideoOverlay interface
  */
@@ -103,6 +107,16 @@ void            gst_video_overlay_prepare_window_handle (GstVideoOverlay * overl
 GST_EXPORT
 gboolean        gst_is_video_overlay_prepare_window_handle_message (GstMessage * msg);
 
+GST_EXPORT
+void            gst_video_overlay_install_properties    (GObjectClass    * oclass,
+                                                         gint              last_prop_id);
+
+GST_EXPORT
+gboolean        gst_video_overlay_set_property          (GObject         * object,
+                                                         gint              last_prop_id,
+                                                         guint             property_id,
+                                                         const GValue    * value);
+
 G_END_DECLS
 
 #endif /* __GST_VIDEO_OVERLAY_H__ */