[GTK] Off-by-one error in getStyleContext()

https://bugs.webkit.org/show_bug.cgi?id=151524

Reviewed by Carlos Garcia Campos.

GtkWidgetPath* path = gtk_widget_path_new();
gtk_widget_path_append_type(path, widgetType);
// ...
gtk_widget_path_iter_add_class(path, 0, GTK_STYLE_CLASS_BUTTON);
gtk_widget_path_iter_add_class(path, 1, "text-button");

Only one widget type was appended to the widget path, so the maximum valid index is 0. This
code means to add both style classes to the first widget type in the widget path, so the
second call should use index 0 rather than index 1.

This caused no bug in practice, because when the index is invalid,
gtk_widget_path_iter_add_class() automatically changes the index to the last valid position
in the widget path -- in this case, 0. This is routinely done with -1 as a convention for
specifying the last position in the widget path.

* rendering/RenderThemeGtk.cpp:
(WebCore::getStyleContext):


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@192724 268f45cc-cd09-0410-ab3c-d52691b4dbfc

Author: [email protected]

Source/WebCore/ChangeLog

@@ -1,3 +1,28 @@
+2015-11-21  Michael Catanzaro  <[email protected]>
+
+        [GTK] Off-by-one error in getStyleContext()
+        https://bugs.webkit.org/show_bug.cgi?id=151524
+
+        Reviewed by Carlos Garcia Campos.
+
+        GtkWidgetPath* path = gtk_widget_path_new();
+        gtk_widget_path_append_type(path, widgetType);
+        // ...
+        gtk_widget_path_iter_add_class(path, 0, GTK_STYLE_CLASS_BUTTON);
+        gtk_widget_path_iter_add_class(path, 1, "text-button");
+
+        Only one widget type was appended to the widget path, so the maximum valid index is 0. This
+        code means to add both style classes to the first widget type in the widget path, so the
+        second call should use index 0 rather than index 1.
+
+        This caused no bug in practice, because when the index is invalid,
+        gtk_widget_path_iter_add_class() automatically changes the index to the last valid position
+        in the widget path -- in this case, 0. This is routinely done with -1 as a convention for
+        specifying the last position in the widget path.
+
+        * rendering/RenderThemeGtk.cpp:
+        (WebCore::getStyleContext):
+
 2015-11-21  Michael Catanzaro  <[email protected]>
 
         [GTK] Warning spam from GtkStyleContext

Source/WebCore/rendering/RenderThemeGtk.cpp

@@ -175,7 +175,7 @@ static GtkStyleContext* getStyleContext(GType widgetType)
         gtk_widget_path_iter_add_class(path, 0, "arrow");
     else if (widgetType == GTK_TYPE_BUTTON) {
         gtk_widget_path_iter_add_class(path, 0, GTK_STYLE_CLASS_BUTTON);
-        gtk_widget_path_iter_add_class(path, 1, "text-button");
+        gtk_widget_path_iter_add_class(path, 0, "text-button");
     } else if (widgetType == GTK_TYPE_SCALE)
         gtk_widget_path_iter_add_class(path, 0, GTK_STYLE_CLASS_SCALE);
     else if (widgetType == GTK_TYPE_SEPARATOR)