1625226 - Ctrl+Tab preview thumbnails are weirdly cropped with devtools open

Status: NEW

(Firefox :: Tabbed Browser, defect, P3)

Description

[Kris Taeleman (:ktaeleman)]

When switching tabs when devtools is open on one of the tabs, the tab with devtools will render incorrectly in the tabs switching preview.

STR:

• Open a site and enable devtools
• Open 3 more tabs on different sites
• Press and hold ctrl-tab to show tab preview
  Notice that the tab with devtools is rendered incorrectly. It also shows the wrong layout

Comment 1

[Kris Taeleman (:ktaeleman)]

Attachment: Wrong preview

Comment 2

[Kris Taeleman (:ktaeleman)]

Attachment: Actual page

Comment 3

[Daniel Holbert [:dholbert]]

I think the code lives here:
https://searchfox.org/mozilla-central/rev/4ccefc3181f9d237ef4ca8bd17b4e7c101ddf7b5/browser/base/content/browser-ctrlTab.js

and presumably this is a bug in the code that gets run for the "capture" function there.

That seems to invoke https://searchfox.org/mozilla-central/rev/4ccefc3181f9d237ef4ca8bd17b4e7c101ddf7b5/toolkit/components/thumbnails/PageThumbs.jsm#324

I think this code all lives in the "Tabbed Browser" component. There are some layout/graphics APIs involved somewhere, but it's not obvious that they're where the problem lies (as opposed to the JS code that captures/prepares/etc. the preview). Hence, reclassifying as Tabbed Browser for now, since that's the component responsible for managing this UI & these previews.

Comment 4

[Firefox Bug Husbandry Bot]

Because this bug's Severity has not been changed from the default since it was filed, and it's Priority is P3 (Backlog,) indicating it has been triaged, the bug's Severity is being updated to S3 (normal.)