dmabuf-paintable: Build the texture when snapshot is called

Always creating the texture even if the app is not being displayed
(minimized / different virtual monitor) or
if the GdkFrameClock drops a frame we end up doing a comparison with a
very old frame causing full redraws in certain cases or even artifacts
in others.

Instead, we only build the texture once snapshot is called and accumulate
the damage area until that happens to avoid updating the wrong area

lib/mks-dmabuf-paintable.c

@@ -35,67 +35,20 @@
  * so we can pass the damage region to `GdkGLTextureBuilder`.
  */
 
-struct _MksDmabufPaintable
-{
-  GObject parent_instance;
-  GdkTexture *texture;
-  guint width;
-  guint height;
-};
-
 typedef struct _MksDmabufTextureData
 {
   GdkGLContext *gl_context;
   GLuint texture_id;
 } MksDmabufTextureData;
 
-static int
+struct _MksDmabufPaintable
-mks_dmabuf_paintable_get_intrinsic_width (GdkPaintable *paintable)
 {
-  return MKS_DMABUF_PAINTABLE (paintable)->width;
+  GObject parent_instance;
-}
+  GdkTexture *texture;
-
+  GdkGLTextureBuilder *builder;
-static int
+  guint width;
-mks_dmabuf_paintable_get_intrinsic_height (GdkPaintable *paintable)
+  guint height;
-{
+};
-  return MKS_DMABUF_PAINTABLE (paintable)->height;
-}
-
-static double
-mks_dmabuf_paintable_get_intrinsic_aspect_ratio (GdkPaintable *paintable)
-{
-  MksDmabufPaintable *self = MKS_DMABUF_PAINTABLE (paintable);
-
-  return (double)self->width / (double)self->height;
-}
-
-static void
-mks_dmabuf_paintable_snapshot (GdkPaintable *paintable,
-                               GdkSnapshot  *snapshot,
-                               double        width,
-                               double        height)
-{
-  MksDmabufPaintable *self = (MksDmabufPaintable *)paintable;
-  graphene_rect_t area;
-
-  g_assert (MKS_IS_DMABUF_PAINTABLE (self));
-  g_assert (GDK_IS_SNAPSHOT (snapshot));
-
-  area = GRAPHENE_RECT_INIT (0, 0, width, height);
-  gtk_snapshot_append_texture (snapshot, self->texture, &area);
-}
-
-static void
-paintable_iface_init (GdkPaintableInterface *iface)
-{
-  iface->get_intrinsic_width = mks_dmabuf_paintable_get_intrinsic_width;
-  iface->get_intrinsic_height = mks_dmabuf_paintable_get_intrinsic_height;
-  iface->get_intrinsic_aspect_ratio = mks_dmabuf_paintable_get_intrinsic_aspect_ratio;
-  iface->snapshot = mks_dmabuf_paintable_snapshot;
-}
-
-G_DEFINE_FINAL_TYPE_WITH_CODE (MksDmabufPaintable, mks_dmabuf_paintable, G_TYPE_OBJECT,
-                               G_IMPLEMENT_INTERFACE (GDK_TYPE_PAINTABLE, paintable_iface_init))
 
 static MksDmabufTextureData *
 mks_dmabuf_texture_data_new (GdkGLContext *gl_context,
@@ -127,12 +80,76 @@ mks_dmabuf_texture_data_free (gpointer data)
   g_free (texture_data);
 }
 
+static int
+mks_dmabuf_paintable_get_intrinsic_width (GdkPaintable *paintable)
+{
+  return MKS_DMABUF_PAINTABLE (paintable)->width;
+}
+
+static int
+mks_dmabuf_paintable_get_intrinsic_height (GdkPaintable *paintable)
+{
+  return MKS_DMABUF_PAINTABLE (paintable)->height;
+}
+
+static double
+mks_dmabuf_paintable_get_intrinsic_aspect_ratio (GdkPaintable *paintable)
+{
+  MksDmabufPaintable *self = MKS_DMABUF_PAINTABLE (paintable);
+
+  return (double)self->width / (double)self->height;
+}
+
+static void
+mks_dmabuf_paintable_snapshot (GdkPaintable *paintable,
+                               GdkSnapshot  *snapshot,
+                               double        width,
+                               double        height)
+{
+  MksDmabufPaintable *self = (MksDmabufPaintable *)paintable;
+  g_autoptr(GdkTexture) texture = NULL;
+  GdkGLContext *gl_context;
+  GLuint texture_id;
+  graphene_rect_t area;
+
+  g_assert (MKS_IS_DMABUF_PAINTABLE (self));
+  g_assert (GDK_IS_SNAPSHOT (snapshot));
+
+  texture_id = gdk_gl_texture_builder_get_id (self->builder);
+  gl_context = gdk_gl_texture_builder_get_context (self->builder);
+
+  gdk_gl_texture_builder_set_update_texture (self->builder, self->texture);
+  texture = gdk_gl_texture_builder_build (self->builder,
+                                          mks_dmabuf_texture_data_free,
+                                          mks_dmabuf_texture_data_new (gl_context, 
+                                                                       texture_id));
+  // Clear up the update region to not union it with the next UpdateDMABuf call
+  gdk_gl_texture_builder_set_update_region (self->builder, NULL);
+  g_set_object (&self->texture, texture);
+
+  area = GRAPHENE_RECT_INIT (0, 0, width, height);
+  gtk_snapshot_append_texture (snapshot, self->texture, &area);
+}
+
+static void
+paintable_iface_init (GdkPaintableInterface *iface)
+{
+  iface->get_intrinsic_width = mks_dmabuf_paintable_get_intrinsic_width;
+  iface->get_intrinsic_height = mks_dmabuf_paintable_get_intrinsic_height;
+  iface->get_intrinsic_aspect_ratio = mks_dmabuf_paintable_get_intrinsic_aspect_ratio;
+  iface->snapshot = mks_dmabuf_paintable_snapshot;
+}
+
+G_DEFINE_FINAL_TYPE_WITH_CODE (MksDmabufPaintable, mks_dmabuf_paintable, G_TYPE_OBJECT,
+                               G_IMPLEMENT_INTERFACE (GDK_TYPE_PAINTABLE, paintable_iface_init))
+
 static void
 mks_dmabuf_paintable_dispose (GObject *object)
 {
   MksDmabufPaintable *self = (MksDmabufPaintable *)object;
 
   g_clear_object (&self->texture);
+  g_clear_object (&self->builder);
 
   G_OBJECT_CLASS (mks_dmabuf_paintable_parent_class)->dispose (object);
 }
@@ -157,8 +174,8 @@ mks_dmabuf_paintable_import (MksDmabufPaintable   *self,
                              cairo_region_t       *region,
                              GError              **error)
 {
-  g_autoptr(GdkGLTextureBuilder) builder = NULL;
+  cairo_region_t *accumulated_damages;
-  g_autoptr(GdkTexture) texture = NULL;
+  cairo_region_t *previous_region;
   GLuint texture_id;
   guint zero = 0;
 
@@ -204,25 +221,32 @@ mks_dmabuf_paintable_import (MksDmabufPaintable   *self,
       return FALSE;
     }
 
-  builder = gdk_gl_texture_builder_new ();
+  accumulated_damages = cairo_region_create ();
-  gdk_gl_texture_builder_set_id (builder, texture_id);
-  gdk_gl_texture_builder_set_width (builder, self->width);
-  gdk_gl_texture_builder_set_height (builder, self->height);
-  gdk_gl_texture_builder_set_context (builder, gl_context);
 
   if (region != NULL)
+    cairo_region_union (accumulated_damages, region);
+
+  if (self->builder != NULL)
     {
-      gdk_gl_texture_builder_set_update_region (builder, region);
+      previous_region = gdk_gl_texture_builder_get_update_region (self->builder);
-      gdk_gl_texture_builder_set_update_texture (builder, self->texture);
+      if (previous_region != NULL)
+        cairo_region_union (accumulated_damages, previous_region);
     }
 
-  texture = gdk_gl_texture_builder_build (builder,
+  g_clear_object (&self->builder);
-                                          mks_dmabuf_texture_data_free,
-                                          mks_dmabuf_texture_data_new (gl_context, texture_id));
 
-  g_set_object (&self->texture, texture);
+  self->builder = gdk_gl_texture_builder_new ();
+  gdk_gl_texture_builder_set_width (self->builder, self->width);
+  gdk_gl_texture_builder_set_height (self->builder, self->height);
+  gdk_gl_texture_builder_set_context (self->builder, gl_context);
+  gdk_gl_texture_builder_set_id (self->builder, texture_id);
+
+  if (cairo_region_num_rectangles (accumulated_damages) > 0)
+    gdk_gl_texture_builder_set_update_region (self->builder,
+                                              accumulated_damages);
+
+  g_clear_pointer (&accumulated_damages, cairo_region_destroy);
   gdk_paintable_invalidate_contents (GDK_PAINTABLE (self));
-
   return TRUE;
 }