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core-animationcalayerdrawrectcgcontext

CALayer renderInContext: Position of Drawing

I have a UIView with a custom shape drawn in drawRect:. The frame property is set to:

{5.f, 6.f, 50.f, 50.f}

Now, I render the view in an Image Context, but it is ignoring the frame property of the UIView, and always drawing the UIView in the top left.

[_shapeView.layer renderInContext:UIGraphicsGetCurrentContext()];

I tried to change the frame of the CALayer, but nothing changed. Modifying the bounds property made things worse. The only work around I found useful was:

CGRect frame = _shapeView.frame;
CGContextTranslateCTM(context, frame.origin.x, frame.origin.y);
[_shapeView.layer renderInContext:context];

But, this is impractical when I am dealing with many shapes, I want to just use the frame property.

Solution

  • Using CGContextTranslateCTM is the proper way to go. As renderInContext: documentation states : "Renders in the coordinate space of the layer." This means the frame origin of your layer/view is ignored.

    Regarding CGContextDrawLayer, it is not made to be used with CALayer, but with CGLayer. These are two very different things, and explains your crash.