1952343 - "Load and diff" not working on Nightly Linux

Status: RESOLVED FIXED

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

Description

[Alex Franchuk [:afranchuk]]

I tried about:memory "Load and diff" on Nightly 138.0a1 (2025-03-05). After the first file dialog appeared and selecting a file, a second was never shown and no memory information was shown. I then tried on Release 135.0 and that worked as expected.

Comment 1

[Andrew McCreight [:mccr8]]

This works for me on MacOS Nightly, and this code has not changed in forever, so I suspect a file picker widget issue?

Comment 2

[Alice0775 White]

I can reproduce the issue on Nightly138.0a1 ubuntu24.04 GNOME.
Regression window:
https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=1fe06d3ac98b2ab9be5fb354e6595f819004b10c&tochange=e49da4b8b2d09f51ba9072863281bbc23e787c0a

Comment 3

[Alice0775 White]

And confirmed that if set browser.disable_pickers_background_tabs to false, then it works as expected.

Comment 5

[Donal Meehan [:dmeehan]]

Pinged :edgar in Slack to ask to look at this

Comment 6

[Edgar Chen [:edgar]]

I could not reproduce this on Windows, either. It looks like this only occurs on Linux.

Comment 7

[Edgar Chen [:edgar]]

Hmm, I think this is caused by the platform difference. The file picker causes the browser window to lose focus. about:memory attempts to open the file picker again after the first file is selected by waiting for the change event, and that occurs before the focus is switched back to the browser window on Linux, whereas other platform that occurs after the focus has switched back to the browser window.

I tried to "delay" the gtk response for file picker by scheduling it for the next event loop iteration. However, that didn't help; the focus switch still occurred later. It is probably not easy to make Linux behave like other platforms.

I created a similar case and tested it on Chrome, Chrome also block the second file picker on Linux, so I am not concerned about web compatibility.

I think we could either make about:memory check and wait the focus before attempting to open the picker again, or allow about page to open picker in background. I would opt for the former solution first. If more use cases arise on about pages, we could consider excluding them from the check.

Comment 8

[Andrew McCreight [:mccr8]]

The double file picker thing is very odd so a specific work around sounds good to me.

Comment 9

[Edgar Chen [:edgar]]

Attachment: Bug 1952343 - Notify nsI{Color|File}PickerShownCallback asynchronously when picker is blocked; r?emilio

Otherwise, the HTMLInputElement doesn't handle the mPickerRunning flag right if
it is in parent process. There is no such problem on content process because
the IPC is async.

Comment 10

[Edgar Chen [:edgar]]

Attachment: Bug 1952343 - [about:memory] Wait for document to regain focus before reopening the file picker; r?mccr8

Comment 11

[Donal Meehan [:dmeehan]]

Next week is the final week of beta for Fx137.
Looks like this is on track to land in Fx138 and potentially uplift to Fx137 if needed.

Comment 12

[Andrew McCreight [:mccr8]]

That should be fine. While I could see a user looking at about:memory, doing diffs of them is a very niche activity so it is likely not very common for people to do.

Comment 13

[Andrew McCreight [:mccr8]]

Plus somebody can always save memory reports from an affected version, then do a diff in a fixed version.

Comment 14

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/60d4fd3913aa
Notify nsI{Color|File}PickerShownCallback asynchronously when picker is blocked; r=emilio
https://hg.mozilla.org/integration/autoland/rev/bb4a8e6e5b41
[about:memory] Wait for document to regain focus before reopening the file picker; r=mccr8

Comment 15

[amarc]

Backed out for causing linting failure

• Backout link
• Push with failures
• Failure Log

Comment 16

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/011e15bbbe66
Notify nsI{Color|File}PickerShownCallback asynchronously when picker is blocked; r=emilio
https://hg.mozilla.org/integration/autoland/rev/f809c12942b6
[about:memory] Wait for document to regain focus before reopening the file picker; r=mccr8

Comment 17

[amarc]

https://hg.mozilla.org/mozilla-central/rev/011e15bbbe66
https://hg.mozilla.org/mozilla-central/rev/f809c12942b6

Comment 18

[BugBot [:suhaib / :marco/ :calixte]]

The patch landed in nightly and beta is affected.
:edgar, is this bug important enough to require an uplift?

• If yes, please nominate the patch for beta approval.
• If no, please set status-firefox137 to wontfix.

For more information, please visit BugBot documentation.

Comment 19

[Edgar Chen [:edgar]]

This is a developer feature and not common to use, developer can use a fixed version to open diff.