Open Radar

 
Summary:
The Comics app has run into a problem on iOS7 running on the iPad Air. 

Comics is an 32-bit app which runs on iOS 5, 6 and 7. When running on the iPad Air (and only the Air so far) and displaying comics in Guided View mode, it will sometimes stutter and/or not fully display the comic panels in certain situations. Here is a video showing one instance of this. https://cloudup.com/cIF3WwAmuVL

I've been able to put together a sample application which demonstrates the problem. It seems that certain combinations of translation/scale factors when run as a 32-bit app on a 64-bit iPad Air fail to render the view hierarchy completely to the screen. Either not drawing the final state at all or stuttering as it animates from one scale/translation to another.

http://cl.ly/3b1l0y0K281s

If this same app is run as a 64-bit app, this does not happen.

Steps to Reproduce:
1. Download and compile included sample application
2. Run application using the ScalingBug-32bit scheme on an iPad Air in PORTRAIT orientation.
3. Tap the screen to change the view transforms
    (Each tap should center and scale to fit a specific panel (or full page) on screen)
4. On the 3rd tap, notice that the image either stutters as it animates, or simply doesn't complete the animation to it's new position/scale.
   (the panel with the Hah! speech bubble - 3rd panel from the top - should be centered on screen)
5. On the 4th tap, notice that the image jumps, then animates to its new position.
6. More taps will cycle through all the positions again.
7. Notice that on the 6th tap when scaling back to showing the entire image, the animation stutters part way through.


Expected Results:
All scale/translations are displayed correctly.

Actual Results:
Image is not in correct final position.

Version:
iOS 7.0.3 (11B511)

Notes:
If we change the scale factor we're transforming our view hierarchy by then we can get the final image position to display, but at the wrong scale.  Testing had indicated that it's a specific combination of scale and translation of the view hierarchy on screen. Increasing the scale factor (say 2x) does not demonstrate the bug.

Configuration:
Occurs on iPad Air iOS 7.0.3 (11B511)
DOES NOT Occur on any other iPad, iPhone or iPod Touch running any iOS version