Vertical scrolling arrows in bookmark bar folder windows when needed....

chrome/browser/cocoa/bookmark_bar_folder_controller.h

 // Copyright (c) 2010 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #import <Cocoa/Cocoa.h>
 
 #include "base/scoped_nsobject.h"
 #import "chrome/browser/cocoa/bookmark_button.h"
 
 @class BookmarkBarController;
@@ skipping 46 matching lines @@
   // Our buttons.  We do not have buttons for nested folders.
   scoped_nsobject<NSMutableArray> buttons_;
 
   // The scroll view that contains our main button view (below).
   IBOutlet NSScrollView* scrollView_;
 
   // Are we scrollable?  If no, the full contents of the folder are
   // always visible.
   BOOL scrollable_;
 
+  BOOL scrollUpArrowShown_;
+  BOOL scrollDownArrowShown_;
+
   // The main view of this window (where the buttons go).
   IBOutlet BookmarkBarFolderView* mainView_;
 
   // Weak; we keep track to work around a
   // setShowsBorderOnlyWhileMouseInside bug.
   BookmarkButton* buttonThatMouseIsIn_;
 
   // The context menu for a bookmark button which represents an URL.
   IBOutlet NSMenu* buttonMenu_;
 
@@ skipping 16 matching lines @@
 
   // Implement basic menu scrolling through this tracking area.
   scoped_nsobject<NSTrackingArea> scrollTrackingArea_;
 
   // Timer to continue scrolling as needed.  We own the timer but
   // don't release it when done (we invalidate it).
   NSTimer* scrollTimer_;
 
   // Amount to scroll by on each timer fire.  Can be + or -.
   CGFloat verticalScrollDelta_;
+
+  // We need to know the size of the vertical scrolling arrows so we
+  // can obscure/unobscure them.
+  CGFloat verticalScrollArrowHeight_;
 }
 
 // Designated initializer.
 - (id)initWithParentButton:(BookmarkButton*)button
           parentController:(BookmarkBarFolderController*)parentController
              barController:(BookmarkBarController*)barController;
 
 // Return the parent button that owns the bookmark folder we represent.
 - (BookmarkButton*)parentButton;
 
@@ skipping 30 matching lines @@
 @end
 
 @interface BookmarkBarFolderController(TestingAPI)
 - (NSView*)mainView;
 - (NSPoint)windowTopLeft;
 - (NSArray*)buttons;
 - (BookmarkBarFolderController*)folderController;
 - (id)folderTarget;
 - (void)configureWindowLevel;
 - (void)performOneScroll:(CGFloat)delta;
+
+// Return YES if we can scroll up or down.
+- (BOOL)canScrollUp;
+- (BOOL)canScrollDown;
+
 @end