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.

diff --git a/gtk/gtkstylecontext.c b/gtk/gtkstylecontext.c
index 8c99d8f26f63be0a9c74062a2aed749b8bf244a7..d1b8854a4cdf1bc4b4c90f1c2190667900df5c9e 100644 (file)
--- 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);
     }
 }