From 2cd9e5170e0da6b9c8d92fab21c7b8541edb2738 Mon Sep 17 00:00:00 2001
From: Benjamin Otte <otte@redhat.com>
Date: Sun, 13 Nov 2016 16:37:35 +0100
Subject: [PATCH] widget: Add more sophisticated detection of rendering method

We now look at which of get_render_mode, draw or snapshot vfuncs is the
latest to have been overwritten in the class tree and then use that one.

This allows GtkContainerClass and GtkBinClass to override all of them
for without screwing things up.
---
 gtk/gtkwidget.c | 43 ++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 38 insertions(+), 5 deletions(-)

diff --git a/gtk/gtkwidget.c b/gtk/gtkwidget.c
index 7b805483d8..0f70589cd0 100644
--- a/gtk/gtkwidget.c
+++ b/gtk/gtkwidget.c
@@ -6318,6 +6318,34 @@ gtk_cairo_should_draw_window (cairo_t   *cr,
   return tmp == window;
 }
 
+typedef enum {
+  RENDER_SNAPSHOT,
+  RENDER_GET_RENDER_NODE,
+  RENDER_DRAW
+} RenderMode;
+
+static RenderMode
+get_render_mode (GtkWidgetClass *klass)
+{
+  GtkWidgetClass *parent_class;
+
+  for (parent_class = g_type_class_peek_parent (klass);
+       parent_class != gtk_widget_parent_class;
+       parent_class = g_type_class_peek_parent (klass))
+    {
+      if (klass->snapshot != parent_class->snapshot)
+        return RENDER_SNAPSHOT;
+      else if (klass->get_render_node != parent_class->get_render_node)
+        return RENDER_GET_RENDER_NODE;
+      else if (klass->draw != parent_class->draw)
+        return RENDER_DRAW;
+
+      klass = parent_class;
+    }
+
+  return RENDER_SNAPSHOT;
+}
+
 void
 gtk_widget_draw_internal (GtkWidget *widget,
                           cairo_t   *cr,
@@ -6342,6 +6370,7 @@ gtk_widget_draw_internal (GtkWidget *widget,
       GdkWindow *event_window = NULL;
       gboolean result;
       gboolean push_group;
+      RenderMode mode;
 
       /* If this was a cairo_t passed via gtk_widget_draw() then we don't
        * require a window; otherwise we check for the window associated
@@ -6375,7 +6404,9 @@ gtk_widget_draw_internal (GtkWidget *widget,
        * render on the Cairo context; otherwise we just go through the old
        * GtkWidget::draw path
        */
-      if (widget_class->snapshot != NULL)
+      mode = get_render_mode (widget_class);
+
+      if (mode == RENDER_SNAPSHOT)
         {
           GskRenderer *renderer = gtk_widget_get_renderer (widget);
           GtkSnapshot snapshot;
@@ -6400,7 +6431,7 @@ gtk_widget_draw_internal (GtkWidget *widget,
 
           g_object_unref (fallback);
         }
-      else if (widget_class->get_render_node != NULL)
+      else if (mode == RENDER_GET_RENDER_NODE)
         {
           GskRenderer *renderer = gtk_widget_get_renderer (widget);
           GskRenderer *fallback;
@@ -15674,6 +15705,7 @@ gtk_widget_snapshot (GtkWidget   *widget,
   graphene_rect_t bounds;
   GtkAllocation clip;
   GtkAllocation alloc;
+  RenderMode mode;
 
   if (_gtk_widget_get_alloc_needed (widget))
     return;
@@ -15685,8 +15717,9 @@ gtk_widget_snapshot (GtkWidget   *widget,
   /* Compatibility mode: if the widget does not have a render node, we draw
    * using gtk_widget_draw() on a temporary node
    */
-  if (klass->get_render_node == NULL &&
-      klass->snapshot == NULL)
+  mode = get_render_mode (klass);
+
+  if (mode == RENDER_DRAW)
     {
       cairo_t *cr;
 
@@ -15701,7 +15734,7 @@ gtk_widget_snapshot (GtkWidget   *widget,
       if (g_signal_has_handler_pending (widget, widget_signals[DRAW], 0, FALSE))
         gtk_snapshot_push (snapshot, &bounds, "DrawSignal<%s>", G_OBJECT_TYPE_NAME (widget));
 
-      if (klass->snapshot)
+      if (mode == RENDER_SNAPSHOT)
         klass->snapshot (widget, snapshot);
       else
         {
-- 
2.30.2