theme: Do not create temporary GtkStyle objects

In order to pick up colors from a GtkStyleContext, a temporary
GtkStyle object was created from the context and destroyed after
copying the requested GdkColor. This is slightly inefficient, so
get the appropriate GdkRGBA from the context and translate it to
a GdkColor, based on the compatibility code in gtkstyle.c.

https://bugzilla.gnome.org/show_bug.cgi?id=645355

src/ui/theme.c

@@ -1415,20 +1415,112 @@ meta_color_spec_new_gtk (MetaGtkColorComponent component,
   return spec;
 }
 
+/* Based on set_color() in gtkstyle.c */
+#define LIGHTNESS_MULT 1.3
+#define DARKNESS_MULT  0.7
+static void
+meta_set_color_from_style (GdkColor              *color,
+                           GtkStyleContext       *context,
+                           GtkStateType           state,
+                           MetaGtkColorComponent  component)
+{
+  GdkRGBA *rgba_color = NULL;
+  GtkStateFlags flags;
+
+  switch (state)
+    {
+    case GTK_STATE_ACTIVE:
+      flags = GTK_STATE_FLAG_ACTIVE;
+      break;
+    case GTK_STATE_PRELIGHT:
+      flags = GTK_STATE_FLAG_PRELIGHT;
+      break;
+    case GTK_STATE_SELECTED:
+      flags = GTK_STATE_FLAG_SELECTED;
+      break;
+    case GTK_STATE_INSENSITIVE:
+      flags = GTK_STATE_FLAG_INSENSITIVE;
+      break;
+    default:
+      flags = 0;
+    }
+
+  switch (component)
+    {
+    case META_GTK_COLOR_BG:
+    case META_GTK_COLOR_BASE:
+    case META_GTK_COLOR_MID:
+    case META_GTK_COLOR_LIGHT:
+    case META_GTK_COLOR_DARK:
+      gtk_style_context_get (context, flags,
+                             "background-color", &rgba_color,
+                             NULL);
+      break;
+    case META_GTK_COLOR_FG:
+    case META_GTK_COLOR_TEXT:
+    case META_GTK_COLOR_TEXT_AA:
+      gtk_style_context_get (context, flags,
+                             "color", &rgba_color,
+                             NULL);
+      break;
+    case META_GTK_COLOR_LAST:
+      g_assert_not_reached ();
+      break;
+    }
+
+  if (rgba_color)
+    {
+      color->pixel = 0;
+      color->red = CLAMP ((guint) (rgba_color->red * 65535), 0, 65535);
+      color->green = CLAMP ((guint) (rgba_color->green * 65535), 0, 65535);
+      color->blue = CLAMP ((guint) (rgba_color->blue * 65535), 0, 65535);
+      gdk_rgba_free (rgba_color);
+    }
+  else
+    {
+      meta_warning (_("Failed to retrieve color %s[%s] from GTK+ theme.\n"),
+                    meta_color_component_to_string (component),
+                    meta_gtk_state_to_string (state));
+      color->pixel = 0;
+      color->red = component == META_GTK_COLOR_TEXT ? 0 : 65535;
+      color->green = 0;
+      color->blue = component == META_GTK_COLOR_TEXT ? 0 : 65535;
+    }
+
+  if (component == META_GTK_COLOR_LIGHT)
+    gtk_style_shade (color, color, LIGHTNESS_MULT);
+  else if (component == META_GTK_COLOR_DARK)
+    gtk_style_shade (color, color, DARKNESS_MULT);
+  else if (component == META_GTK_COLOR_MID)
+    {
+      GdkColor light, dark;
+
+      gtk_style_shade (color, &light, LIGHTNESS_MULT);
+      gtk_style_shade (color, &dark, DARKNESS_MULT);
+
+      color->red = (light.red + dark.red) / 2;
+      color->green = (light.green + dark.green) / 2;
+      color->blue = (light.blue + dark.blue) / 2;
+    }
+  else if (component == META_GTK_COLOR_TEXT_AA)
+    {
+      GdkColor base;
+
+      meta_set_color_from_style (&base, context, state, META_GTK_COLOR_BASE);
+      color->red = (color->red + base.red) / 2;
+      color->green = (color->green + base.green) / 2;
+      color->blue = (color->blue + base.blue) / 2;
+    }
+}
+
 void
 meta_color_spec_render (MetaColorSpec   *spec,
                         GtkStyleContext *context,
                         GdkColor        *color)
 {
-  GtkStyle *style;
-
   g_return_if_fail (spec != NULL);
   g_return_if_fail (GTK_IS_STYLE_CONTEXT (context));
 
-  style = g_object_new (GTK_TYPE_STYLE,
-                        "context", context,
-                        NULL);
-
   switch (spec->type)
     {
     case META_COLOR_SPEC_BASIC:
@@ -1436,36 +1528,10 @@ meta_color_spec_render (MetaColorSpec   *spec,
       break;
 
     case META_COLOR_SPEC_GTK:
-      switch (spec->data.gtk.component)
+      meta_set_color_from_style (color,
-        {
+                                 context,
-        case META_GTK_COLOR_BG:
+                                 spec->data.gtk.state,
-          *color = style->bg[spec->data.gtk.state];
+                                 spec->data.gtk.component);
-          break;
-        case META_GTK_COLOR_FG:
-          *color = style->fg[spec->data.gtk.state];
-          break;
-        case META_GTK_COLOR_BASE:
-          *color = style->base[spec->data.gtk.state];
-          break;
-        case META_GTK_COLOR_TEXT:
-          *color = style->text[spec->data.gtk.state];
-          break;
-        case META_GTK_COLOR_LIGHT:
-          *color = style->light[spec->data.gtk.state];
-          break;
-        case META_GTK_COLOR_DARK:
-          *color = style->dark[spec->data.gtk.state];
-          break;
-        case META_GTK_COLOR_MID:
-          *color = style->mid[spec->data.gtk.state];
-          break;
-        case META_GTK_COLOR_TEXT_AA:
-          *color = style->text_aa[spec->data.gtk.state];
-          break;
-        case META_GTK_COLOR_LAST:
-          g_assert_not_reached ();
-          break;
-        }
       break;
 
     case META_COLOR_SPEC_BLEND:
@@ -1494,8 +1560,6 @@ meta_color_spec_render (MetaColorSpec   *spec,
       }
       break;
     }
-
-  g_object_unref (style);
 }
 
 /**