1532291 - Tabbing out of a component which has tabindex -1 and shadow root freezes the browser

Status: RESOLVED FIXED

(Core :: DOM: Core & HTML, defect, P2)

Description

[Vilimantas Bernotaitis]

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/72.0.3626.119 Safari/537.36

Steps to reproduce:

1. Create simple web component with shadow DOM, slot and tabindex=-1.
2. Nest component in the same component, add several levels.
3. Focus node in the top level and press tab.

Here is the code example:
https://codepen.io/anon/pen/ywJqzm

Actual results:

Browser freezes (time of freeze depends on nested levels)

Expected results:

Next focusable element is focused.

Comment 1

[Alice0775 White]

I can reproduce the gang on Nightly67.0a1 windows10.

Comment 2

[Alice0775 White]

s/gang/hang/

Comment 3

[Alice0775 White]

Regression window:
https://hg.mozilla.org/integration/mozilla-inbound/pushloghtml?fromchange=97898f7472fb0f9e73f4edfb27b2b25e05fd9611&tochange=0dad5cbc6165abc5e395bfb3be995b0da69e7212

Regressed by:
0dad5cbc6165 Olli Pettay — Bug 1466581, handle sequential focus also in nested shadow DOM, r=mrbkap

Comment 4

[Olli Pettay [:smaug][[e-mail]]]

Thanks Alice!

Comment 5

[Tim Spurway [:tspurway]]

Setting to fix-optional for 66 b/c P2

Comment 6

[Olli Pettay [:smaug][[e-mail]]]

Interesting. It isn't a hang, but (very) slow performance.

Comment 7

[Olli Pettay [:smaug][[e-mail]]]

Attachment: shadow_dom_nested_sequential_focus.diff

Need to write a testcase tomorrow

Comment 8

[Olli Pettay [:smaug][[e-mail]]]

remote: https://treeherder.mozilla.org/#/jobs?repo=try&revision=3a951f769ed33aa1135c9952ccc9bcac49da5cd0

Comment 9

[Olli Pettay [:smaug][[e-mail]]]

Attachment: Bug 1532291, bail out early when trying to find any focusable element in shadow tree, r=masayuki

If aIgnoreTabIndex is true, we're just trying to find any focusable element, doesn't matter which tabindex it has.
So better to bail out early from the deeply nested GetNextTabbableContentInScope to avoid exponential number of calls.

Comment 10

[Olli Pettay [:smaug][[e-mail]]]

filed bug 1535320 to rename the test file

Comment 11

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/mozilla-inbound/rev/0cc6396199a8
bail out early when trying to find any focusable element in shadow tree, r=masayuki

Comment 12

[Razvan Maries]

https://hg.mozilla.org/mozilla-central/rev/0cc6396199a8