gdk: Track wether windows have alpha in the background

This will let us handle such windows differently in the
drawing machinery

diff --git a/gdk/gdkinternals.h b/gdk/gdkinternals.h
index 27afe026ac402fa349ab1cb2b770e791b37b8512..9bd1ea9e651d501f5cbbcd65732a17ad23a6e4e3 100644 (file)
--- a/gdk/gdkinternals.h
+++ b/gdk/gdkinternals.h
@@ -204,6 +204,7 @@ struct _GdkWindow
   guint input_only : 1;
   guint modal_hint : 1;
   guint composited : 1;
+  guint has_alpha_background : 1;
 
   guint destroyed : 2;
 

diff --git a/gdk/gdkwindow.c b/gdk/gdkwindow.c
index dba089704f2be24fee7a83a02281bd75768bfaf9..ae0850c58bfd21f4d93be159d1c307acffd14a8a 100644 (file)
--- a/gdk/gdkwindow.c
+++ b/gdk/gdkwindow.c
@@ -6476,6 +6476,9 @@ void
 gdk_window_set_background_pattern (GdkWindow *window,
                                    cairo_pattern_t *pattern)
 {
+  gboolean has_alpha;
+  cairo_pattern_type_t type;
+  
   g_return_if_fail (GDK_IS_WINDOW (window));
 
   if (window->input_only)
@@ -6487,6 +6490,54 @@ gdk_window_set_background_pattern (GdkWindow *window,
     cairo_pattern_destroy (window->background);
   window->background = pattern;
 
+  has_alpha = TRUE;
+  type = cairo_pattern_get_type (pattern);
+  
+  if (type == CAIRO_PATTERN_TYPE_SOLID)
+    {
+      double alpha;
+      cairo_pattern_get_rgba (pattern, NULL, NULL, NULL, &alpha);
+      if (alpha == 1.0)
+       has_alpha = FALSE;
+    }
+  else if (type == CAIRO_PATTERN_TYPE_LINEAR ||
+          type == CAIRO_PATTERN_TYPE_RADIAL)
+    {
+      int i, n;
+      double alpha;
+
+      n = 0;
+      cairo_pattern_get_color_stop_count (pattern, &n);
+      has_alpha = FALSE;
+      for (i = 0; i < n; i++)
+       {
+         cairo_pattern_get_color_stop_rgba (pattern, i, NULL,
+                                            NULL, NULL, NULL, &alpha);
+         if (alpha != 1.0)
+           {
+             has_alpha = TRUE;
+             break;
+           }
+       }
+    }
+  else if (type == CAIRO_PATTERN_TYPE_SURFACE)
+    {
+      cairo_surface_t *surface;
+      cairo_content_t content;
+
+      cairo_pattern_get_surface (pattern, &surface);
+      content = cairo_surface_get_content (surface);
+      has_alpha =
+       (content == CAIRO_CONTENT_ALPHA) ||
+       (content == CAIRO_CONTENT_COLOR_ALPHA);
+    }
+  
+  if (has_alpha != window->has_alpha_background)
+    {
+      window->has_alpha_background = has_alpha;  
+      recompute_visible_regions (window, TRUE, FALSE);
+    }
+  
   if (gdk_window_has_impl (window))
     {
       GdkWindowImplClass *impl_class = GDK_WINDOW_IMPL_GET_CLASS (window->impl);