paintable: Introduce gdk_paintable_new_empty()

Also, use it where appropriate.

docs/reference/gdk/gdk4-sections.txt

@@ -717,6 +717,7 @@ gdk_paintable_get_intrinsic_aspect_ratio
 gdk_paintable_compute_concrete_size
 gdk_paintable_invalidate_contents
 gdk_paintable_invalidate_size
+gdk_paintable_new_empty
 <SECTION>
 
 <SECTION>

gdk/gdkpaintable.c

@@ -544,3 +544,102 @@ gdk_paintable_compute_concrete_size (GdkPaintable *paintable,
     }
 }
 
+#define GDK_TYPE_EMPTY_PAINTABLE (gdk_empty_paintable_get_type())
+static
+G_DECLARE_FINAL_TYPE(GdkEmptyPaintable, gdk_empty_paintable, GDK, EMPTY_PAINTABLE, GObject)
+
+struct _GdkEmptyPaintable
+{
+  GObject parent_instance;
+
+  int width;
+  int height;
+};
+
+struct _GdkEmptyPaintableClass
+{
+  GObjectClass parent_class;
+};
+
+static void
+gdk_empty_paintable_snapshot (GdkPaintable *paintable,
+                              GdkSnapshot  *snapshot,
+                              double        width,
+                              double        height)
+{
+}
+
+static GdkPaintableFlags
+gdk_empty_paintable_get_flags (GdkPaintable *paintable)
+{
+  return GDK_PAINTABLE_STATIC_SIZE
+       | GDK_PAINTABLE_STATIC_CONTENTS;
+}
+
+static int
+gdk_empty_paintable_get_intrinsic_width (GdkPaintable *paintable)
+{
+  GdkEmptyPaintable *self = GDK_EMPTY_PAINTABLE (paintable);
+
+  return self->width;
+}
+
+static int
+gdk_empty_paintable_get_intrinsic_height (GdkPaintable *paintable)
+{
+  GdkEmptyPaintable *self = GDK_EMPTY_PAINTABLE (paintable);
+
+  return self->height;
+}
+
+static void
+gdk_empty_paintable_paintable_init (GdkPaintableInterface *iface)
+{
+  iface->snapshot = gdk_empty_paintable_snapshot;
+  iface->get_flags = gdk_empty_paintable_get_flags;
+  iface->get_intrinsic_width = gdk_empty_paintable_get_intrinsic_width;
+  iface->get_intrinsic_height = gdk_empty_paintable_get_intrinsic_height;
+}
+
+G_DEFINE_TYPE_WITH_CODE (GdkEmptyPaintable, gdk_empty_paintable, G_TYPE_OBJECT,
+                         G_IMPLEMENT_INTERFACE (GDK_TYPE_PAINTABLE,
+                                                gdk_empty_paintable_paintable_init))
+
+static void
+gdk_empty_paintable_class_init (GdkEmptyPaintableClass *klass)
+{
+}
+
+static void
+gdk_empty_paintable_init (GdkEmptyPaintable *self)
+{
+}
+
+/**
+ * gdk_paintable_new_empty:
+ * @intrinsic_width: The intrinsic width to report. Can be 0 for no width.
+ * @intrinsic_height: The intrinsic height to report. Can be 0 for no height.
+ *
+ * Returns a paintable that has the given intrinsic size and draws nothing.
+ * This is often useful for implementing the GdkPaintableClass:get_current_image()
+ * virtual function when the paintable is in an incomplete state (like a
+ * #GtkMediaStream before receiving the first frame).
+ *
+ * Returns: (transfer full) a #GdkPaintable
+ **/
+GdkPaintable *
+gdk_paintable_new_empty (int intrinsic_width,
+                         int intrinsic_height)
+{
+  GdkEmptyPaintable *result;
+
+  g_return_val_if_fail (intrinsic_width < 0, NULL);
+  g_return_val_if_fail (intrinsic_height < 0, NULL);
+
+  result = g_object_new (GDK_TYPE_EMPTY_PAINTABLE, NULL);
+
+  result->width = intrinsic_width;
+  result->height = intrinsic_height;
+
+  return GDK_PAINTABLE (result);
+}

gdk/gdkpaintable.h

@@ -135,6 +135,9 @@ GDK_AVAILABLE_IN_ALL
 void            gdk_paintable_invalidate_contents       (GdkPaintable           *paintable);
 GDK_AVAILABLE_IN_ALL
 void            gdk_paintable_invalidate_size           (GdkPaintable           *paintable);
+GDK_AVAILABLE_IN_ALL
+GdkPaintable *  gdk_paintable_new_empty                 (int                     intrinsic_width,
+                                                         int                     intrinsic_height);
 
 
 G_END_DECLS

modules/media/gtkffmediafile.c

@@ -114,6 +114,14 @@ gtk_ff_media_file_paintable_get_current_image (GdkPaintable *paintable)
 {
   GtkFfMediaFile *video = GTK_FF_MEDIA_FILE (paintable);
 
+  if (gtk_video_frame_ffmpeg_is_empty (&video->current_frame))
+    {
+      if (video->codec_ctx)
+        return gdk_paintable_new_empty (video->codec_ctx->width, video->codec_ctx->height);
+      else
+        return gdk_paintable_new_empty (0, 0);
+    }
+
   return GDK_PAINTABLE (g_object_ref (video->current_frame.texture));
 }
 

modules/media/gtkgstpaintable.c

@@ -57,8 +57,7 @@ gtk_gst_paintable_paintable_get_current_image (GdkPaintable *paintable)
   if (self->image)
     return GDK_PAINTABLE (g_object_ref (self->image));
 
-  g_warning ("FIXME: return empty something here");
-  return NULL;
+  return gdk_paintable_new_empty (0, 0);
 }
 
 static int