Not sure if removing the floorf() is a great solution, as it will cause views to be rendered on half pixels.

Rendering on half pixels isn't possible? Fairly sure you want to keep the precision in your views' frames. It's working fine for me.

it's possible, but it will be slower.

I'm encountering this issue as well.

I think the best solution would be to rework the autoresizing logic in UIView.m to always base the autoresized frame (& bounds?) on an internal "original frame" CGRect rather than self.frame. That original frame would be set to the last frame set by an outside caller (i.e, not the autoresizing logic) by a call to -setFrame:, and the autoresizing logic would pretend the superview resized from the original frame to the new frame in one step. This would prevent the rounding error from accumulating, and fix the 'drifting' problem @silvermana and I noticed.

I tried hacking up that solution but couldn't get it to work. :( Maybe someone else wants to take a stab at it?

In the meantime, removing the floorf function from that line, as @silvermana suggested, fixed the immediate problem so I'm going to go with that for the time being.