WKWebView crashes in acceleratedAnimationDidStart

Question

I'm having a crash occur on a client's app and other than a lot at the WTFCrash, I'm not getting much use out of the stack trace.

I am using a WKWebView instance to show a web page that has some CSS based animations and a video. The issues occurs on iOS 8 and 9 over a wide variety of devices (iPhone 5c to a 6s and a similar range of iPads).

The WKWebView runs in its own process, not the application's. When the crash occurs a white layer is left behind that covers the main application, rendering it inaccessible even thought its process has not been affected.

Looking at the device logs I find crashes from the com.apple.WebKit.WebContent process and they all have the exact same log for the crashed thread.

Thread 0 name:  Dispatch queue: com.apple.main-thread
Thread 0 Crashed:
0   JavaScriptCore                  0x0000000184c9f22c WTFCrash + 72
1   JavaScriptCore                  0x0000000184c9f224 WTFCrash + 64
2   WebKit                          0x0000000188ecd850 WebKit::RemoteLayerTreeDrawingArea::acceleratedAnimationDidStart(unsigned long long, WTF::String const&, double) + 0
3   WebCore                         0x0000000184f2e70c WebCore::ThreadTimers::sharedTimerFiredInternal() + 148
4   WebCore                         0x0000000184f2e64c WebCore::timerFired(__CFRunLoopTimer*, void*) + 36
5   CoreFoundation                  0x000000018107d81c __CFRUNLOOP_IS_CALLING_OUT_TO_A_TIMER_CALLBACK_FUNCTION__ + 28
6   CoreFoundation                  0x000000018107d4c0 __CFRunLoopDoTimer + 884
7   CoreFoundation                  0x000000018107abd4 __CFRunLoopRun + 1520
8   CoreFoundation                  0x0000000180fa4d10 CFRunLoopRunSpecific + 384
9   Foundation                      0x00000001819b4d8c -[NSRunLoop(NSRunLoop) runMode:beforeDate:] + 308
10  Foundation                      0x0000000181a09ff8 -[NSRunLoop(NSRunLoop) run] + 88
11  libxpc.dylib                    0x0000000180d68cf8 _xpc_objc_main + 660
12  libxpc.dylib                    0x0000000180d6aa2c xpc_main + 200
13  com.apple.WebKit.WebContent     0x0000000100057924 0x100054000 + 14628
14  libdyld.dylib                   0x0000000180b428b8 start + 4

Here is some sample html/css that we use to reproduce the issue.

        var initialWidth = 100;
        window.addEventListener('load', function() {
          var div = document.getElementById('mytest');
          div.className = '';
          setInterval(function() {
            initialWidth += 10;
            if (initialWidth > 1000) {
              initialWidth = 1;
            }
            div.style.height = initialWidth + 'px';
          }, 40);
        }, false);

        body {
          background-color: #4cb9e4;
        }
        
        div#mytest {
          position: absolute;
          top: 0;
          width: 100%;
          height: 5000px;
          background-color: rgba(0, 0, 0, 0.7);
          text-align: center;
          overflow-y: hidden;
          -webkit-transition-property: height;
          -moz-transition-property: height;
          transition-property: height;
          -webkit-transition-duration: 0.5s;
          -moz-transition-duration: 0.5s;
          transition-duration: 0.5s;
          -webkit-transition-timing-function: ease;
          -moz-transition-timing-function: ease;
          transition-timing-function: ease;
        }
        
        div#mytest.hidden {
          height: 0;
        }

    <body>
      <div class="hidden" id="mytest">
        This is sample test
      </div>
    </body>

Does this look familiar to anybody? Is there something I should tell the web engineer to change with regards to the animation?

you really need to provide additional information for this issue to get a worthwhile response. Webviews can be very quirky and a pain to deal with, you need as much info as possible to diagnose them — Scriptable, May 20 '16 at 23:26
Did you ever find a solution to this? I have 1 user of my app that is getting WebContent crashes from a WKWebView — Darren, Sep 30 '19 at 15:05

score 1 · Answer 1 · answered Aug 25 '18 at 07:45

You should create the webView in the main thread

- (void)createWebView{
    if (![NSThread isMainThread]) {
        dispatch_async(dispatch_get_main_queue(), ^{
            [self createWebView];
        });
        return;
    }
    self.webView = [[UIWebView alloc] initWithFrame:CGRectMake(0, 0, 320, 320)];
    //Rest of my code
}

WKWebView crashes in acceleratedAnimationDidStart

1 Answers1