firefox nightly: weird grey top bar & reload button randomly added to uBO's extension UI

[ComfortableMilk4454]

Prerequisites

• [X] I verified that this is not a filter list issue. Report any issues with filter lists or broken website functionality in the uAssets issue tracker.
• [X] This is NOT a YouTube, Facebook or Twitch report. These sites MUST be reported by clicking their respective links.
• [X] This is not a support issue or a question. For support, questions, or help, visit /r/uBlockOrigin.
• [X] I performed a cursory search of the issue tracker to avoid opening a duplicate issue.
• [X] The issue is not present after disabling uBO in the browser.
• [X] I checked the documentation to understand that the issue I am reporting is not normal behavior.

I tried to reproduce the issue when...

• [X] uBO is the only extension.
• [X] uBO uses default lists and settings.
• [X] using a new, unmodified browser profile.

Description

firefox nightly: weird grey top bar that disappears after a few seconds and when that happens reload button gets randomly added to uBO's extension UI (see screen recording): THIS ONLY HAPPENS UPON LAUNCHING NIGHTLY & CLICKING ON UBO'S EXTENSION ICON, NOT WHEN NAVIGATING TO A NEW TAB WITH NIGHTLY ALREADY RUNNING & CLICKING ON UBO'S EXTENSION ICON. fyi if you saw i have adguard running on my mac dw i made sure to turn it off for firefox, so this issue is not caused by "stacking" adblockers

A specific URL where the issue occurs.

new nightly tab

Steps to Reproduce

1. click on uBO's icon

Expected behavior

no bar at the top & no refresh button appearing

Actual behavior

bar at the top & refresh button appears

uBO version

1.58.0

Browser name and version

Firefox Nightly 129.0a1 (2024-06-28) (64-bit) & all versions of nightly over the past month or so

Operating System and version

macOS 14.5 (23F79)

[gorhill]

That grey bar is where the hostname of the current site appears normally, and if it's not filled with the hostname at browser launch it's simply because uBO's background process has not yet been fully initialized. It gets filled in once the background process is initialized and ready to answer requests from the popup panel.

[ComfortableMilk4454]

i see. so this is a nightly issue then, because this doesn't happen on firefox release, right? thanks for explaining.

[gorhill]

Not necessarily a Nightly issue. There is a lot of thing which can prevent uBO's background process from answering in a timely manner to requests from its auxiliary page. In Firefox all extensions execute in the same process, so even another extension hogging the webextensions process could affect responsiveness in other extensions. It could be a delay originating from Firefox itself, for example https://bugzilla.mozilla.org/show_bug.cgi?id=1899015.

Profiling at browser launch would maybe help identify the sequence of events. In any case, there is no malfunction, it's just that there is a delay between the popup requesting information from the background process, and the background process answering that delay.

I could add a non-breakable whitespace character as placeholder to ensure the vertical size of the grey bar does not change.

[garry-ut99]

Not only a Firefox Nightly issue, as the same occurs also on Firefox Release on a fresh browser profile. Currently doesn't occur in Chromium and Edge, so it's related to Firefox. However it was happening also in Chromium and Edge in the past, but not anymore, as still can be reproduced in old browsers like Chromium 109 or Edge 109.

this only happens upon launching nightly & clicking on ubo's extension icon

Or by turning off & on uBlock in browser extension pane (Firefox). In old Chromium 109 or Edge 109, I still need to use "restarting browser" method to reproduce. Method might depend on how fast is CPU, as different users have different CPUs.

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Also similiar to (or even might be related or duplicate, as big power button is white for a while in the both issues):

• https://github.com/uBlockOrigin/uBlock-issues/issues/757