Bug 218533 – Toggling pointer-events on body does not re-enable scrolling on child

• Component: UI Events
• Status: RESOLVED FIXED

[Liam DeBeasi]

Created attachment 413103 [details]
Code Reproduction

Setting `pointer-events: none` on the body and then removing it does not re-enable scrolling on descendent scrollable elements.

Steps to Reproduce:

1. Open attached code reproduction on an iPhone running iOS 14.0 or newer.
2. Verify that you can scroll the page.
3. Tap the "Tap to Disable Scrolling" button. Verify that you can no longer scroll the page. This adds `pointer-events: none` to the body.
4. After 3000ms `pointer-events: none` will be removed from the body. At this point, you should not be able to scroll, even though `pointer-events: none` has been removed.
5. Tap the "Tap me to fix scrolling" button. After doing this, you should be able to scroll again.


Expected Behavior:

After removing `pointer-events: none` from the body, I would expect to be able to scroll again.


Actual Behavior:

After removing `pointer-events: none` from the body, I am unable to scroll.


Additional Information:

* I had opened a similar issue for iOS 12.2, but that bug went away with iOS 13.0: https://bugs.webkit.org/show_bug.cgi?id=195801.
* This was tested on an iPhone 11 running iOS 14.2, but I can reproduce it on iOS 14.0.1 and iOS 14.1 as well.
* I cannot reproduce this on iOS 13.6.
* I cannot reproduce this on Safari for macOS.

[Radar WebKit Bug Importer]

<rdar://problem/71009746>

[Simon Fraser (smfr)]

Need to check to see if we correctly regenerate the event regions.

[Devin Rousso]

Created attachment 414561 [details]
Patch

I'd love to have a way to test this.  Uploading to EWS to see if any existing tests have issues (and therefore might be able to be used to derive my own test).

[Antoine Quint]

Can you not write a test that scrolls and check whether scrolling occurred? You can take a look at LayoutTests/pointerevents tests which, although testing a different feature, will likely show examples of that.

[Devin Rousso]

(In reply to Antoine Quint from comment #4)
> Can you not write a test that scrolls and check whether scrolling occurred? You can take a look at LayoutTests/pointerevents tests which, although testing a different feature, will likely show examples of that.
Oh nice!  I was going to ask someone about this tomorrow.  Thanks! :)

FYI I marked it as cq- because it did not have tests.  I should've said "I don't know how to write a test for this." instead in comment #3.

[Simon Fraser (smfr)]

Comment on attachment 414561 [details]
Patch

Needs a test. See fast/scrolling/ios/body-overflow-hidden.html for an example of how to test scrolling

[Devin Rousso]

Created attachment 415173 [details]
Patch

[EWS]

Committed r270339: <https://trac.webkit.org/changeset/270339>

All reviewed patches have been landed. Closing bug and clearing flags on attachment 415173 [details].

[Simon Fraser (smfr)]

The test is failing in EWS

[Truitt Savell]

The new test fast/scrolling/ios/overflow-scroll-pointer-events.html
is timing out on iOS constantly.

History:
https://results.webkit.org/?suite=layout-tests&test=fast%2Fscrolling%2Fios%2Foverflow-scroll-pointer-events.html

[WebKit Commit Bot]

Re-opened since this is blocked by bug 219441

[Truitt Savell]

Reverted r270339 for reason:

introduced a constantly failing test.

Committed r270363: <https://trac.webkit.org/changeset/270363>

[Devin Rousso]

Created attachment 416209 [details]
Patch

improved test to not fail :)

[EWS]

Committed r270849: <https://trac.webkit.org/changeset/270849>

All reviewed patches have been landed. Closing bug and clearing flags on attachment 416209 [details].