1933994 - Out of process iframe small flicker after switching browser window

Status: NEW

(Core :: Layout, defect)

Description

[Bogdan Maris, Desktop Test Engineering [OOO until 14th April]]]

Attachment: Video showing the issue

Found in

• Firefox 134.0b1

Affected versions

• Firefox 134.0b1
• Nightly 135.0a1

Tested platforms

• Affected platforms: Windows 11
• Unaffected platforms: macOS, Ubuntu

Preconditions

• Have 'Combine taskbar buttons and hide labels' option to 'Never'. Option can be found in Personalization > Taskbar > Taskbar Behaviors from Windows settings.

Steps to reproduce
Steps imported from bug 1927255 comment 0

1. Start Nightly and have it maximized (lets say window-A)
2. Open https://codepen.io/cssence/pen/abeVWYK
3. Resize the results pane so that there will be no scrollbar
4. Open new window (lets say window-B)
5. Click (slightly long mouse button press) the task button to switch between both browser windows
6. Repeat step.5

Expected result

• The results pane should always be drawn and no flicker is shown.

Actual result

• After step 6 there is sometimes a small flicker inside the pane.

Regression range

• Not a regression, this is just a small flicker remaining after another fixed bug, bug 1927255

Additional notes

• Originally bug 1927255. It has received a fix but there still is a small flicker which although it was decided that the fix is acceptable (and I agree). I also decided to keep track of this though even it will not end up being addressed.
• The last 5-6 seconds from the video shows the flicker.