[gtk+] stylecontext: Fix gtk_style_context_set_background()

[Benjamin Otte <otte src gnome org>]

commit 5e12aafacdacfd5b03f358a6cd0262d539e480af
Author: Benjamin Otte <otte redhat com>
Date:   Mon Dec 17 16:42:55 2012 +0100

    stylecontext: Fix gtk_style_context_set_background()
    
    This function is just a sophisitcated optimization.
    
    If we know the GDK window's background will be opaque, we mark it as
    opaque. This is so GDK can do all the optimizations it does for opaque
    windows and be fast.
    
    This is mainly used when scrolling.
    
    The previous code didn't get this right, in particular it didn't enforce
    a transparent background when it knew the background was not opaque.

 gtk/gtkstylecontext.c |   36 ++++++++++++++++++++++++++++--------
 1 files changed, 28 insertions(+), 8 deletions(-)
---
diff --git a/gtk/gtkstylecontext.c b/gtk/gtkstylecontext.c
index 8c99d8f..d1b8854 100644
--- a/gtk/gtkstylecontext.c
+++ b/gtk/gtkstylecontext.c
@@ -25,6 +25,7 @@
 #include "gtkstylecontextprivate.h"
 #include "gtkcontainerprivate.h"
 #include "gtkcsscolorvalueprivate.h"
+#include "gtkcsscornervalueprivate.h"
 #include "gtkcssenginevalueprivate.h"
 #include "gtkcssnumbervalueprivate.h"
 #include "gtkcssrgbavalueprivate.h"
@@ -3230,6 +3231,13 @@ gtk_style_context_invalidate (GtkStyleContext *context)
   _gtk_bitmask_free (changes);
 }
 
+static gboolean
+corner_value_is_right_angle (GtkCssValue *value)
+{
+  return _gtk_css_corner_value_get_x (value, 100) <= 0.0 &&
+         _gtk_css_corner_value_get_y (value, 100) <= 0.0;
+}
+
 /**
  * gtk_style_context_set_background:
  * @context: a #GtkStyleContext
@@ -3244,21 +3252,33 @@ void
 gtk_style_context_set_background (GtkStyleContext *context,
                                   GdkWindow       *window)
 {
-  GtkStateFlags state;
-  GdkRGBA *color;
+  const GdkRGBA *color;
 
   g_return_if_fail (GTK_IS_STYLE_CONTEXT (context));
   g_return_if_fail (GDK_IS_WINDOW (window));
 
-  state = gtk_style_context_get_state (context);
+  /* This is a sophisitcated optimization.
+   * If we know the GDK window's background will be opaque, we mark
+   * it as opaque. This is so GDK can do all the optimizations it does
+   * for opaque windows and be fast.
+   * This is mainly used when scrolling.
+   *
+   * We could indeed just set black instead of the color we have.
+   */
+  color = _gtk_css_rgba_value_get_rgba (_gtk_style_context_peek_property (context, GTK_CSS_PROPERTY_BACKGROUND_COLOR));
 
-  gtk_style_context_get (context, state,
-                         "background-color", &color,
-                         NULL);
-  if (color)
+  if (color->alpha >= 1.0 &&
+      corner_value_is_right_angle (_gtk_style_context_peek_property (context, GTK_CSS_PROPERTY_BORDER_TOP_LEFT_RADIUS)) &&
+      corner_value_is_right_angle (_gtk_style_context_peek_property (context, GTK_CSS_PROPERTY_BORDER_TOP_RIGHT_RADIUS)) &&
+      corner_value_is_right_angle (_gtk_style_context_peek_property (context, GTK_CSS_PROPERTY_BORDER_BOTTOM_RIGHT_RADIUS)) &&
+      corner_value_is_right_angle (_gtk_style_context_peek_property (context, GTK_CSS_PROPERTY_BORDER_BOTTOM_LEFT_RADIUS)))
     {
       gdk_window_set_background_rgba (window, color);
-      gdk_rgba_free (color);
+    }
+  else
+    {
+      GdkRGBA transparent = { 0.0, 0.0, 0.0, 0.0 };
+      gdk_window_set_background_rgba (window, &transparent);
     }
 }