Cocoa：自定义NSTableHeaderView高度和背景颜色

Question

我尝试更改NSTableHeaderView的高度，高度已更改，但背景上有一块白色。这是我的代码：

    for subView:NSView in topScrollView.subviews {
        for subSubView:NSView in subView.subviews {
            if (subSubView is NSTableHeaderView) && (subView is NSClipView) {
                subSubView.setFrameSize(NSMakeSize(subSubView.frame.size.width, subSubView.frame.size.height + 20))
                subView.setFrameSize(NSMakeSize(subView.frame.size.width, subView.frame.size.height + 20))
            }
        }
    }

和快照

感谢您的帮助〜