问题描述
我有一个自定义层支持的 NSView 并覆盖了 makeBackingLayer 方法以返回自定义 CALayer 子类.我还覆盖了 WantUpdateLayer 以返回 true 从而完全选择类似图层的绘图.
I have a custom layer-backed NSView and have overidden the makeBackingLayer method to return a custom CALayer subclass. I have also overriden wantsUpdateLayer to return true thereby fully opting into layer-like drawing.
override func makeBackingLayer() -> CALayer {
return Layer() // my custom class with "drawLayer:" implemented
}
override var wantsUpdateLayer:Bool{
return true
}
// never called
override func updateLayer() {
super.updateLayer()
println("updateLayer after")
self.layer?.borderWidth += 1
}
执行此操作后,我发现当我设置 NSView.needsDisplay = true
时,它会将调用路由到自定义层的 drawInContext: 方法,而不是 updateLayer: 方法.为什么这样做?在我的示例中,我已经检查过,如果我删除了 makeBackingLayer
覆盖,那么我的 updateLayer
将以预期的方式调用.
Once I do this, I find that when I set NSView.needsDisplay = true
it routes calls to the custom layer's drawInContext: method as opposed to the updateLayer: method. Why does it do this? In my example, I have checked that if I remove the makeBackingLayer
override then my updateLayer
is called in the expected manner.
我不太明白,但其他实例指出,当您的 makeBackingLayer 返回自定义
CALayer` 时,您实际上将自定义层托管在父支持层内.(本人纯属猜测)
I can't quite put my finger on it, but other instances point to the notion that when your makeBackingLayerreturns a custom
CALayer` that you actually have your custom layer hosted inside a parent backing layer. (Pure Speculation on my part)
此外,考虑到 CALayer 的 drawInContext: 更低级",两条绘制路线之间会不会有不同的性能特征?有关该问题的更多详细信息,请参阅此 SO 问题:Layer支持 NSView 性能,直接在 CALayer.drawInContext 中渲染:
Further, would there be different performance characteristics between the two drawing routes given that CALayer's drawInContext: is more "low-level"? See this SO question for more detail on that question: Layer-backed NSView performance with rendering directly in CALayer.drawInContext:
任何见解将不胜感激.
推荐答案
你现在肯定已经解决了,但对于未来的读者,我通过阅读 NSView 文档!
Surely you fixed it by now, but for future readers I found a possible explanation by reading the NSView documentation!
如果 canDrawSubviewsIntoLayer
属性设置为 YES,则视图忽略此方法返回的值.相反,视图总是使用它的 drawRect:
方法来绘制它的内容.
这篇关于带有自定义 CALayer 的层支持的 NSView 不调用 updateLayer?的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持!