Core Animation: resizing layer from just one side on iPhone

I want to animate the resize of a CALayer. It needs to expand from the left (the right side needs to stay 开发者_JS百科put). Setting the anchorPoint will make resizes work this way, but once I start animating, it doesn't behave the way I want it to.

Does anyone have a suggestion? Thanks, and sorry for the noob-question.

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Try calculating a new position based on the desired resize, and setting the layer's position at the same time as you set its new bounds.