[Webkit-unassigned] [Bug 167649] [Cocoa] Assertion failure in contentZoomScale(WKWebView *) (scale == [webView->_scrollView zoomScale]) in iOS Mail

bugzilla-daemon at webkit.org bugzilla-daemon at webkit.org
Tue Jan 31 11:21:08 PST 2017


https://bugs.webkit.org/show_bug.cgi?id=167649

--- Comment #2 from mitz at webkit.org <mitz at webkit.org> ---
More information from Simon:

(lldb) po [self recursiveDescription]
<: 0x7f91b3728f10; frame = (0 0; 363 276); gestureRecognizers = <NSArray: 0x620000052240>; layer = <CALayer: 0x6180002226c0>>
   | <UIView: 0x7f91b3730a80; frame = (0 0; 0 0); layer = <CALayer: 0x6180002237c0>>
   | <WKWebView: 0x7f91b481fc00; frame = (0 0; 363 276); autoresize = W+H; layer = <CALayer: 0x6180002219c0>>
   |    | <WKScrollView: 0x7f91b683e800; baseClass = UIScrollView; frame = (0 0; 363 276); clipsToBounds = YES; gestureRecognizers = <NSArray: 0x600000056650>; layer = <CALayer: 0x600000221420>; contentOffset: {0, 0}; contentSize: {0, 0}>
   |    |    | <WKContentView: 0x7f91b6813800; frame = (0 0; 0 0); transform = [0.25, 0, 0, 0.25, 0, 0]; gestureRecognizers = <NSArray: 0x64000004b040>; layer = <CALayer: 0x6000002213e0>>
   |    |    |    | <UIView: 0x7f91b5c0f8f0; frame = (0 0; 0 0); clipsToBounds = YES; layer = <CALayer: 0x64000003b060>>
   |    |    |    |    | <UIView: 0x7f91b5c0f750; frame = (0 0; 0 0); autoresize = W+H; layer = <CALayer: 0x64000003aea0>>
   |    |    |    |    |    | <WKCompositingView: 0x7f91b5b250e0; frame = (0 0; 0 0); layer = <CALayer: 0x62800023e540>> layerID = 1 "<WKCompositingView: 0x7f91b5b250e0>"
   |    |    | <UIView: 0x7f91b5c0fa90; frame = (0 0; 0 0); opaque = NO; layer = <CALayer: 0x64000003b020>>
   |    |    |    | <UITextSelectionView: 0x7f91b5b253f0; frame = (0 0; 0 0); userInteractionEnabled = NO; layer = <CALayer: 0x62800023e560>>
   |    |    | <: 0x7f91b37428a0; frame = (0 0; 0 0); userInteractionEnabled = NO; layer = <CALayer: 0x618000222b00>>
   | <: 0x7f91b3741a10; baseClass = UIStackView; frame = (0 0; 0 0); layer = <CATransformLayer: 0x618000222a40>>


The layer transform is being set via -[UIScrollView setZoomScale:] being called from:
    frame #13: WebKit`::-[WKWebView _didCommitLayerTree:](self=0x00007fb8b00aea00, _cmd="_didCommitLayerTree:", layerTreeTransaction=0x00007fff55f11a00) at WKWebView.mm:1271
    frame #14: WebKit`::-[WKContentView _didCommitLayerTree:](self=0x00007fb8b00b5400, _cmd="_didCommitLayerTree:", layerTreeTransaction=0x00007fff55f11a00) at WKContentView.mm:562
    frame #15: WebKit`WebKit::PageClientImpl::didCommitLayerTree(this=0x0000600000422dc0, layerTreeTransaction=0x00007fff55f11a00) at PageClientImplIOS.mm:506
    frame #16: WebKit`WebKit::WebPageProxy::didCommitLayerTree(this=0x00007fb8b000c018, layerTreeTransaction=0x00007fff55f11a00) at WebPageProxyIOS.mm:407
    frame #17: WebKit`WebKit::RemoteLayerTreeDrawingAreaProxy::commitLayerTree(this=0x00007fb8b41020d0, layerTreeTransaction=0x00007fff55f11a00, scrollingTreeTransaction=0x00007fff55f11b08) at RemoteLayerTreeDrawingAreaProxy.mm:200

but this seems to happen for an offscreen WKWebView (I see this before viewing any message on iPhone). Then the assertion hits when the WKWebView is being resized.

My guess is that the 0.25x scale is some WKWebView content autosizing minimum scale, and the assertion hits when the WKWebView is being prepared for display.

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