gtk: Add GtkContainer API to gather render nodes

We cannot implement GtkWidgetClass.get_render_node() in GtkContainer
without breaking the fallback path that renders a widget to a single
render node rasterization. For GtkContainer subclasses we should provide
a simple API, similar to gtk_container_propagate_draw(), that gathers
all the render nodes for each child.

2 files changed, 41 insertions, 1 deletions

diff --git a/gtk/gtkcontainer.c b/gtk/gtkcontainer.c
index 7e549c4496..26fc804456 100644
--- a/gtk/gtkcontainer.c
+++ b/gtk/gtkcontainer.c
@@ -24,7 +24,6 @@
 
 #include "config.h"
 
-#include "gtkcontainer.h"
 #include "gtkcontainerprivate.h"
 
 #include <stdarg.h>
@@ -54,6 +53,7 @@
 #include "gtkpopovermenu.h"
 #include "gtkshortcutswindow.h"
 
+
 /* A handful of containers inside GTK+ are cheating and widgets
  * inside internal structure as direct children for the purpose
  * of forall().
@@ -3397,3 +3397,38 @@ gtk_container_get_path_for_child (GtkContainer *container,
 
   return path;
 }
+
+typedef struct {
+  GtkContainer *container;
+  GskRenderer *renderer;
+  GskRenderNode *parent;
+} RenderData;
+
+static void
+propagate_render_node (GtkWidget *widget,
+                       gpointer   data_)
+{
+  RenderData *data = data_;
+  GskRenderNode *node;
+
+  node = gtk_widget_get_render_node (widget, data->renderer);
+  if (node != NULL)
+    {
+      gsk_render_node_append_child (data->parent, node);
+      gsk_render_node_unref (node);
+    }
+}
+
+void
+gtk_container_propagate_render_node (GtkContainer  *container,
+                                     GskRenderer   *renderer,
+                                     GskRenderNode *parent_node)
+{
+  RenderData data = {
+    container,
+    renderer,
+    parent_node
+  };
+
+  gtk_container_forall (container, propagate_render_node, &data);
+}
diff --git a/gtk/gtkcontainerprivate.h b/gtk/gtkcontainerprivate.h
index e581df958b..203059106e 100644
--- a/gtk/gtkcontainerprivate.h
+++ b/gtk/gtkcontainerprivate.h
@@ -21,6 +21,7 @@
 #define __GTK_CONTAINER_PRIVATE_H__
 
 #include "gtkcontainer.h"
+#include <gsk/gsk.h>
 
 G_BEGIN_DECLS
 
@@ -42,6 +43,10 @@ void      _gtk_container_maybe_start_idle_sizer (GtkContainer *container);
 void      gtk_container_get_children_clip       (GtkContainer  *container,
                                                  GtkAllocation *out_clip);
 
+void      gtk_container_propagate_render_node   (GtkContainer  *container,
+                                                 GskRenderer   *renderer,
+                                                 GskRenderNode *parent_node);
+
 G_END_DECLS
 
 #endif /* __GTK_CONTAINER_PRIVATE_H__ */