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BB 43236: Disable vsync on Wayland.

Merge Info

Issues

Resolves

Related

  • tor-browser#xxxxx
  • mullvad-browser#xxxxx
  • tor-browser-build#xxxxx

Merging

Target Branches

  • tor-browser - !fixups to tor-browser-specific commits, new features, security backports
  • base-browser and mullvad-browser - !fixups to base-browser-specific commits, new features to be shared with mullvad-browser, and security backports
    • ⚠️ IMPORTANT: Please list the base-browser-specific commits which need to be cherry-picked to the base-browser and mullvad-browser branches here

Target Channels

  • Alpha: esr128-14.5
  • Stable: esr128-14.0
  • Legacy: esr115-13.5

Backporting

Timeline

  • No Backport (preferred): patchset for the next major stable
  • Immediate: patchset needed as soon as possible
  • Next Minor Stable Release: patchset that needs to be verified in nightly before backport
  • Eventually: patchset that needs to be verified in alpha before backport

(Optional) Justification

  • Emergency security update: patchset fixes CVEs, 0-days, etc
    • Not an emergency, but fixes a leak on Wayland (default on Tails!) on non-60Hz displays (not a clue about their spread among Tails users)
  • Censorship event: patchset enables censorship circumvention
  • Critical bug-fix: patchset fixes a bug in core-functionality
  • Consistency: patchset which would make development easier if it were in both the alpha and release branches; developer tools, build system changes, etc
  • Sponsor required: patchset required for sponsor
  • Localization: typos and other localization changes that should be also in the release branch
  • Other: please explain

Issue Tracking

Review

Request Reviewer

  • Request review from an applications developer depending on modified system:
    • NOTE: if the MR modifies multiple areas, please /cc all the relevant reviewers (since Gitlab only allows 1 reviewer)
    • accessibility : henry
    • android : clairehurst, dan
    • build system : boklm
    • extensions : ma1
    • firefox internals (XUL/JS/XPCOM) : jwilde, ma1
    • fonts : pierov
    • frontend (implementation) : henry
    • frontend (review) : donuts, morgan
    • localization : henry, pierov
    • macOS : clairehurst, dan
    • nightly builds : boklm
    • rebases/release-prep : dan, ma1, pierov, morgan
    • security : jwilde, ma1
    • signing : boklm, morgan
    • updater : pierov
    • windows : jwilde, morgan
    • misc/other : pierov, morgan

We need someone with Wayland and a non-60Hz display to validate this (e.g., Rui)!

Change Description

Vsync is enabled by default on Wayland (but Wayland is not enabled by default for us). This leaks the monitor refresh rate on some sites like testufo.com.

How Tested

Manually set this pref to false on about:config, and checked that after that the detected FPS on sites such as testufo.com is 60, rather than the refresh rate of my display (100Hz over HDMI).

I also tested that X11 and Windows don't leak on the same hardware. I couldn't test macOS.

Merge request reports

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