Bug 185001 – Click events on outer page are not being dispatched correctly after touch-zooming within an iframe

• Status: RESOLVED
• Resolution: FIXED
• Component: DOM

[Walter Kalata]

Created attachment 338799 [details]
Iframe Zoom Click Repro

The attached file has an anchor labelled "Click Me" containing an onclick attribute of "alert('Clicked');", as well as an iframe sourced to a youtube video.

Repro:

1.  Focus the video in the iframe
2.  Zoom In
3.  Zoom Out
4.  Click "Click Me" on the parent page

Expectation: "alert('Clicked');" is executed and an alert box displays

Observed:  The click event only seems to dispatch (and the alert box display) a fraction of the time.


Anecdotally, although the link should be at position 0,0 during all of the steps above, document.elementFromPoint(0, 0).click() also fails to result in a dispatched click event to the anchor element during the zoom operation as well.

[Simon Fraser (smfr)]

What do you mean by "focus the video"? Should I tap the play button to start it playing?

[Simon Fraser (smfr)]

Does the bug occur if the "Click me" is not inside position:fixed?

[Radar WebKit Bug Importer]

<rdar://problem/40569615>

[Simon Fraser (smfr)]

Can you put a "click me" outside the position:fixed for testing, and move it away from the edge of the page so that it's easier to test? Does the size of the hit target make any difference?

[Zach]

I have shown the repro in a video here: https://www.youtube.com/watch?v=mqf8vJiu-yY - in the video I have taken the link out of the position: fixed container as well and it persists.

[Sasha]

has there been any progress on this issue? It would really mean a lot. Thanks much.

[Zach]

A temporary workaround we've found is adding a touchstart event handler to the body. After that, the click events work properly and all is good again.

[Walter Kalata]

Created attachment 343530 [details]
Simpler repro, removes unnecessary CSS; still matches the youtube video sent in an earlier comment

[Walter Kalata]

Created attachment 343531 [details]
Workaround -- an empty "ontouchstart" attribute allows for the separate click event to be dispatched.  The reported issue can not be reproduced using this attachment.

[Lucas Forschler]

Mass move bugs into the DOM component.

This is a major issue as my website consists of a feed of embedded youtube videos. UI is rendered useless on iOS. Adding ontouchstart="" to the body works in the beginning, but as the user keeps scrolling the issue presents itself again.

[Simon Fraser (smfr)]

I can reproduce.

[Simon Fraser (smfr)]

The issue is that if you happen to put a finger in the YouTube iframe when zooming, WebPage::updatePotentialTapSecurityOrigin() puts youtube.com's security origin in WebPage::m_potentialTapSecurityOrigin and it doesn't get cleared, causing later potential taps in the main frame to fail.

[Andy Estes]

We assume that any time a touch event is a potential tap, our single tap gesture recognizer will identify the potential tap (even if it never commits). That's a false assumption. In this case, the first touch event in the pinch gesture is a potential tap, but the second touch event occurs before the single tap gesture recognizer identifies a potential tap.

[Andy Estes]

That false assumption causes this bug because we set m_potentialTapSecurityOrigin when a touch event is a potential tap, but never clear it until a potential tap in the WebPage sense either commits or cancels.

I think we can fix this by clearing m_potentialTapSecurityOrigin each time we see a new touch start event.

[Andy Estes]

Created attachment 371254 [details]
Needs a test

[Wenson Hsieh]

Created attachment 373454 [details]
Patch

[Wenson Hsieh]

Created attachment 373455 [details]
Fix open source build

[Wenson Hsieh]

Comment on attachment 373455 [details]
Fix open source build

Thanks for the review!

[WebKit Commit Bot]

Comment on attachment 373455 [details]
Fix open source build

Clearing flags on attachment: 373455

Committed r247161: <https://trac.webkit.org/changeset/247161>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.