algal / autolayoutanchorpointtestrig Goto Github PK

This rig is for examining how autolayout interacts with a view when view.anchorPoint and/or view.transform have non-default values.

To use:

• turn autolayout on/off using the #define in the .pch file in Supporting Files/
• switch between center- and edge- based constraints with the global in ViewController
• turn on/off "frame restoration" on anchorPoint with the global in ViewController

The problem:

• before autolayout, it was easy to set anchorPoint without moving the view by caching the frame
• before autolayout, it was easy to set anchorPoint in the presence of transforms without moving the view, by directly compensating for the transform
• after autolayout, you need to tweak layout constraints to set anchorpoint without moving the view
• after autolayout, it's totally unclear how to compensate how to compensate for transforms in a way analogous to the world before autolayout, because autolayout tries to clobber the effects of some transforms but not others.
• when you're setting an anchorPoint, you're usually also setting a transform, so this is not a corner case

Observations:

• view.center is not the center of view.frame (when anchorPoint and/or transform is non-default)
• autolayout constraints view.center not the center of view frame.