the 'Merge Windows' page context menu item (for Window Merger) is sometimes missing from the page context menu

[grahamperrin]

Maybe exposing a bug in Firefox.

Firefox Multi Account Containers also known as Multi-Account Containers 7.3.0 enabled with Window Merger 0.6.0 and various other extensions.

Cross-reference mozilla/multi-account-containers#1996 (comment)

Zooming in to https://user-images.githubusercontent.com/192271/116799072-baa0bf00-aaed-11eb-9167-14f6144de7f7.png (first of the four shots):

Zooming in to https://user-images.githubusercontent.com/192271/116799079-c3919080-aaed-11eb-854b-11fa8cd22668.png (second shot):

In the first shot, two items are missing from the page context menu:

• Firefox Multi Account Containers
• Merge Windows

My preferences for this extension are not unusual:

[Zegnat]

I haven’t been able to reproduce this.

The only theory I have is that it sometimes just doesn’t get there in time? Does this happen more often right after you have switched to a different window or tab? Currently every focus switch does a full redraw of the menu, but I do not think Firefox updates the context menu while it is open. But in that case, it should show up when you right click a second time.

Going to mark this as help wanted, specifically to see if anyone can come up with reproduction steps!

[grahamperrin]

The sense of randomness is unfortunate.

(If there was no such randomness, it might be easier to find reproducible steps.)

… Does this happen more often right after you have switched to a different window or tab? …

Maybe less often.

From mozilla/multi-account-containers#1996 (comment):

Later I found just one missing (Firefox Multi Account Containers, if I recall correctly). I was unable to take a screenshot, because:

• after bringing Spectacle to the front, then Firefox to the front (probably when Spectacle hid its window during the countdown to a shot), the menu item became usable.

For what it's worth, I do get a sense that the bug is less likely to occur after using Alt-Tab (from one window to the next).