Pulley hangs on iOS 14 Beta 4

[florianbuerger]

After upgrading to iOS 14 Beta 4, even the example projects won't launch anymore and the CPU is at 100%. I didn't have time to investigate further so I don't know if this is a bug from iOS 14 or Pulley. It worked fine until iOS 14 Beta 3.

Anyway, a short term fix I found is to slightly delay the layout code for Pulley with a good old DispatchQueue.main.asyncAfter(deadline: .now() + 0.1) — which, in my initial testing — seems to resolve the issue. See for an example florianbuerger@ea6c287

Just wanted to leave that here in case anyone else is running into it.

[rafaelfrancisco-dev]

This bug started showing up in 14b4, it's an auto layout loop caused by calling view.setNeedsLayout() inside of override open func viewDidLayoutSubviews() when setting the value on the variable currentDisplayMode. For now I've removed the view.setNeedsLayout() from the variable setter, but it might cause unexpected behavior when changing the drawer display mode after it is drawn.

My guess is that this bug is being caused by a faster UI drawing brought by the latest beta, which causes a new re-draw while the call to viewDidLayoutSubviews() hasn't finished yet, you can run your projects with the launch argument -UIViewLayoutFeedbackLoopDebuggingThreshold 100 to better debug this issue.

[andreyz]

Here's a good summary on how to debug auto-layout feedback loops.

[pmacro]

FYI still occurs on Beta 5.

[pmacro]

Around line 597:

changing this:

    public fileprivate(set) var currentDisplayMode: PulleyDisplayMode = .automatic {
        didSet {
            if self.isViewLoaded
            {
                self.view.setNeedsLayout()
            }

            if oldValue != currentDisplayMode
            {

to this:

    public fileprivate(set) var currentDisplayMode: PulleyDisplayMode = .automatic {
        didSet {
            if oldValue != currentDisplayMode
            {
                if self.isViewLoaded
                {
                    self.view.setNeedsLayout()
                }

Fixes it. I don't know this feature or codebase well enough to judge the implications of not running setNeedsLayout when old and new values are the same.

[funkenstrahlen]

I can confirm this issue. Still present on beta 5.

@pmacro Thank you for providing a proposal for a fix! Are you able to open a PR with the fix?

[pmacro]

@funkenstrahlen we only use drawer mode, so my workaround may not work in all cases. I think someone who knows the codebase, and all edge cases, or who has time to discover them, would be better placed to fix this. I posted the workaround mainly to help anyone else who's trying to test the rest of their app for iOS 14 launch.

[ulmentflam]

Hey! Thanks everyone for looking into this issue as I have not had a chance to dive into Xcode 12 yet. I have created the xcode12 branch to start looking into the beta issues with iOS 14 and have included the above patch for this issue, as well as the fix for if the drawer in panel mode and the display mode does not transition. Please continue to test on this branch and let me know what you run into in the betas leading up to the iOS 14 release.

[funkenstrahlen]

Thank you for providing the xcode12 branch with the fix. It does actually improve the situation as the app does not hang on startup anymore.

However when I try to manually change the pulley position state it still starts to hang in an infinite loop.

[stevi-clue]

Hi! When can we expect an updated version of the SDK with the fix?

[ulmentflam]

@florianbuerger is this infinite loop happening when you call setDrawerPosition(position, animated, completion?)?

[florianbuerger]

@ulmentflam I am not 100% sure what you mean. Do you mean in the patched version I linked in my first message?

We have been using Pulley with that fix for a while now and we didn't encounter any more problems. There are no hangs anymore. We are calling setDrawerPosition(position, animated, completion?) often and also directly after launching the app to restore a saved drawer position. We are also using the panel mode on iPad, no issues there as well.

I haven't had time to check out the xcode12 branch.

[ulmentflam]

I'm sorry @florianbuerger, I did mean to tag @funkenstrahlen in my question above who is testing on the xcode12 branch. However, it is good to know that you are not experiencing any other hanging issues with a slight delay in the layout code as I continue to investigate.

[florianbuerger]

@ulmentflam Ah, got it 😄 I'll see if I can test the xcode12 branch this week. Not sure if we need anything else from my fork of Pulley, it has been a while since I looked at that part of the app.

[sohail-niazi]

Hi, I have tried this branch in xcode 12 but app hangs on launch. but it is working fine with xcode 11.

Hey! Thanks everyone for looking into this issue as I have not had a chance to dive into Xcode 12 yet. I have created the xcode12 branch to start looking into the beta issues with iOS 14 and have included the above patch for this issue, as well as the fix for if the drawer in panel mode and the display mode does not transition. Please continue to test on this branch and let me know what you run into in the betas leading up to the iOS 14 release.