[gtk+/wip/ebassi/frame-marker: 17/20] Associate the drawing context to the Cairo context

[Emmanuele Bassi <ebassi src gnome org>]

commit bfb4fe771cbd726df55eeec39a9987ed9956ceee
Author: Emmanuele Bassi <ebassi gnome org>
Date:   Tue Jun 7 16:34:50 2016 +0100

    Associate the drawing context to the Cairo context
    
    Instead of associating the GdkWindow that created the GdkDrawingContext
    we can directly bind the Cairo context to the GDK drawing context.
    
    Cairo contexts created via gdk_cairo_create() go back to not having a
    GdkWindow associated to them, like they did before we introduced the
    gdk_window_begin_draw_frame() API.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=766675

 docs/reference/gdk/gdk3-sections.txt |    2 +-
 gdk/gdkcairo.h                       |    6 ++++--
 gdk/gdkdrawingcontext.c              |   31 +++++++++++++++++++++++++++++++
 gdk/gdkwindow.c                      |   29 -----------------------------
 gtk/gtkwidget.c                      |   29 ++++++++++++++++++-----------
 5 files changed, 54 insertions(+), 43 deletions(-)
---
diff --git a/docs/reference/gdk/gdk3-sections.txt b/docs/reference/gdk/gdk3-sections.txt
index f3e005a..b0fa61f 100644
--- a/docs/reference/gdk/gdk3-sections.txt
+++ b/docs/reference/gdk/gdk3-sections.txt
@@ -625,7 +625,7 @@ gdk_window_create_similar_surface
 gdk_window_create_similar_image_surface
 gdk_cairo_create
 gdk_cairo_get_clip_rectangle
-gdk_cairo_get_window
+gdk_cairo_get_drawing_context
 gdk_cairo_set_source_color
 gdk_cairo_set_source_rgba
 gdk_cairo_set_source_pixbuf
diff --git a/gdk/gdkcairo.h b/gdk/gdkcairo.h
index 4d8d223..6cd50aa 100644
--- a/gdk/gdkcairo.h
+++ b/gdk/gdkcairo.h
@@ -25,6 +25,7 @@
 #include <gdk/gdkversionmacros.h>
 #include <gdk/deprecated/gdkcolor.h>
 #include <gdk/gdkrgba.h>
+#include <gdk/gdkdrawingcontext.h>
 #include <gdk/gdkpixbuf.h>
 #include <pango/pangocairo.h>
 
@@ -32,8 +33,7 @@ G_BEGIN_DECLS
 
 GDK_AVAILABLE_IN_ALL
 cairo_t  * gdk_cairo_create             (GdkWindow          *window);
-GDK_AVAILABLE_IN_3_22
-GdkWindow * gdk_cairo_get_window        (cairo_t            *cr);
+
 GDK_AVAILABLE_IN_ALL
 gboolean   gdk_cairo_get_clip_rectangle (cairo_t            *cr,
                                          GdkRectangle       *rect);
@@ -83,6 +83,8 @@ void       gdk_cairo_draw_from_gl (cairo_t              *cr,
                                    int                   width,
                                    int                   height);
 
+GDK_AVAILABLE_IN_3_22
+GdkDrawingContext *     gdk_cairo_get_drawing_context   (cairo_t *cr);
 
 G_END_DECLS
 
diff --git a/gdk/gdkdrawingcontext.c b/gdk/gdkdrawingcontext.c
index caffa0c..6216bab 100644
--- a/gdk/gdkdrawingcontext.c
+++ b/gdk/gdkdrawingcontext.c
@@ -178,6 +178,34 @@ gdk_drawing_context_init (GdkDrawingContext *self)
 {
 }
 
+static const cairo_user_data_key_t draw_context_key;
+
+static void
+gdk_cairo_set_drawing_context (cairo_t           *cr,
+                               GdkDrawingContext *context)
+{
+  cairo_set_user_data (cr, &draw_context_key, context, NULL);
+}
+
+/**
+ * gdk_cairo_get_drawing_context:
+ * @cr: a Cairo context
+ *
+ * Retrieves the #GdkDrawingContext that created the Cairo
+ * context @cr.
+ *
+ * Returns: (transfer none) (nullable): a #GdkDrawingContext, if any is set
+ *
+ * Since: 3.22
+ */
+GdkDrawingContext *
+gdk_cairo_get_drawing_context (cairo_t *cr)
+{
+  g_return_val_if_fail (cr != NULL, NULL);
+
+  return cairo_get_user_data (cr, &draw_context_key);
+}
+
 /**
  * gdk_drawing_context_get_cairo_context:
  * @context:
@@ -204,6 +232,9 @@ gdk_drawing_context_get_cairo_context (GdkDrawingContext *context)
   if (context->cr == NULL)
     {
       context->cr = gdk_cairo_create (context->window);
+
+      gdk_cairo_set_drawing_context (context->cr, context);
+
       gdk_cairo_region (context->cr, context->clip);
       cairo_clip (context->cr);
     }
diff --git a/gdk/gdkwindow.c b/gdk/gdkwindow.c
index 4724f3f..0f3e222 100644
--- a/gdk/gdkwindow.c
+++ b/gdk/gdkwindow.c
@@ -3111,33 +3111,6 @@ gdk_window_begin_paint_region (GdkWindow            *window,
   gdk_window_begin_paint_internal (window, region);
 }
 
-static const cairo_user_data_key_t draw_context_window_key;
-
-static void
-gdk_cairo_set_window (cairo_t *cr,
-                      GdkWindow *window)
-{
-  cairo_set_user_data (cr, &draw_context_window_key, window, NULL);
-}
-
-/**
- * gdk_cairo_get_window:
- * @cr: a Cairo context created by gdk_window_begin_draw_frame()
- *
- * Retrieves the #GdkWindow that created the Cairo context @cr.
- *
- * Returns: (nullable) (transfer none): a #GdkWindow
- *
- * Since: 3.22
- */
-GdkWindow *
-gdk_cairo_get_window (cairo_t *cr)
-{
-  g_return_val_if_fail (cr != NULL, NULL);
-
-  return cairo_get_user_data (cr, &draw_context_window_key);
-}
-
 /**
  * gdk_window_begin_draw_frame:
  * @window: a #GdkWindow
@@ -3541,8 +3514,6 @@ gdk_cairo_create (GdkWindow *window)
 
   cr = cairo_create (surface);
 
-  gdk_cairo_set_window (cr, window);
-
   if (window->impl_window->current_paint.region != NULL)
     {
       region = cairo_region_copy (window->impl_window->current_paint.region);
diff --git a/gtk/gtkwidget.c b/gtk/gtkwidget.c
index 158e656..313a425 100644
--- a/gtk/gtkwidget.c
+++ b/gtk/gtkwidget.c
@@ -6925,6 +6925,7 @@ gboolean
 gtk_cairo_should_draw_window (cairo_t   *cr,
                               GdkWindow *window)
 {
+  GdkDrawingContext *context;
   GdkWindow *tmp;
 
   g_return_val_if_fail (cr != NULL, FALSE);
@@ -6933,8 +6934,11 @@ gtk_cairo_should_draw_window (cairo_t   *cr,
   if (gtk_cairo_is_marked_for_draw (cr))
     return TRUE;
 
-  tmp = gdk_cairo_get_window (cr);
+  context = gdk_cairo_get_drawing_context (cr);
+  if (context == NULL)
+    return TRUE;
 
+  tmp = gdk_drawing_context_get_window (context);
   if (tmp == NULL)
     return TRUE;
 
@@ -6964,22 +6968,25 @@ gtk_widget_draw_internal (GtkWidget *widget,
 
   if (gdk_cairo_get_clip_rectangle (cr, NULL))
     {
-      GdkWindow *event_window;
+      GdkWindow *event_window = NULL;
       gboolean result;
       gboolean push_group;
 
       /* If this was a cairo_t passed via gtk_widget_draw() then we don't
-       * require a window
+       * require a window; otherwise we check for the window associated
+       * to the drawing context and mark it using the clip region of the
+       * Cairo context.
        */
-      if (gtk_cairo_is_marked_for_draw (cr))
-        {
-          event_window = NULL;
-        }
-      else
+      if (!gtk_cairo_is_marked_for_draw (cr))
         {
-          event_window = gdk_cairo_get_window (cr);
-          if (event_window != NULL)
-            gdk_window_mark_paint_from_clip (event_window, cr);
+          GdkDrawingContext *context = gdk_cairo_get_drawing_context (cr);
+
+          if (context != NULL)
+            {
+              event_window = gdk_drawing_context_get_window (context);
+              if (event_window != NULL)
+                gdk_window_mark_paint_from_clip (event_window, cr);
+            }
         }
 
       push_group =