[gtk+/wip/otte/snapshot: 8/15] widget: Add more sophisticated detection of rendering method

[Benjamin Otte <otte src gnome org>]

commit 2f2b03a78ece304abdf05e7df489b619b7d96883
Author: Benjamin Otte <otte redhat com>
Date:   Sun Nov 13 16:37:35 2016 +0100

    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 files changed, 38 insertions(+), 5 deletions(-)
---
diff --git a/gtk/gtkwidget.c b/gtk/gtkwidget.c
index 6ae5a9d..006edbf 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;
 
@@ -15698,7 +15731,7 @@ gtk_widget_snapshot (GtkWidget   *widget,
     }
   else
     {
-      if (klass->snapshot)
+      if (mode == RENDER_SNAPSHOT)
         klass->snapshot (widget, snapshot);
       else
         {