1857505 - Extension icon/badging updates should only run in visible/painting browser windows

Status: NEW

(WebExtensions :: Frontend, defect, P3)

Description

[:Gijs (he/him)]

+++ This bug was initially created as a clone of Bug #1780207 +++

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Firefox/102.0

Steps to reproduce:

[Cause an extension to update] with 30 plus upwards windows open. This issue can be felt moderately with perhaps 20 windows onwards, and severely from 50 windows onwards. Nowadays, Firefox completely and utterly stalls my whole computer [when this happens].

This is a problem with any and all add-ons that have updating icons (number indicators, etc.) in the menu toolbar - the common factor being that the browser updates the UI in each window, causing the stalling/freezing effect.

<snip>

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bug 1780207 was originally filed primarily about the downloads panel but in the hope of a generic fix. The fix that landed in bug 1781090 was specific to the downloads panel, and I've morphed 1780207 to address the remainder of the downloads panel issue - but it'd probably be worth updating badge/icon updates for downloads buttons to be queued until the button is visible. Especially now that many icons will be in the extension menu and thus not visible at all until the panel is opened, not affecting the DOM unless/until it's visible will probably help save us CPU and GPU cycles.