Firefox Nightly 103.0a1 UI refreshes at 60Hz on a 120Hz panel with privacy.resistFingerprinting enabled

[slashdragos]

Open any website and start scrolling. Firefox Nightly 103.0a1 refreshes at 60Hz on a 120Hz panel.

On a 120Hz panel, Firefox should scroll at 120 FPS.

Firefox 103 only displays 60 FPS on a 120Hz panel.

Note that this behaviour cannot be reproduced within Settings menu.

I can reproduce this issue on both Galaxy Note20 Ultra (N9860) and Galaxy S22 Ultra (N908B), both running Android 12. This issue has been present for less than 48 hours, so it only affects the last few builds published on PlayStore as of 05/05/2022.

Nightly 103:

Stable 101:

┆Issue is synchronized with this Jira Task

[Mugurell]

Duplicate of #20630

[Mugurell]

@slashdragos In regards to the issue it is more of a platform limitation - the underlying surface the webpage is drawn on has that limit of only updating at 60Hz but some OEMs will choose to allow certain application to render at an even higher framerate. Like it happens on most devices for the release version of Firefox.
Firefox Nightly unfortunately doesn't generally benefit of that exemption from the 60Hz limit but at the moment this is not something that we can control.

[slashdragos]

I did some more testing this morning, and upon a fresh install of Nightly, everything works fine at 120Hz.
I did find the culprit, although this might be intended behaviour: "privacy.resistFingerprinting" limits Firefox to 60 fps. It would be nice if I could keep privacy.resistFingerprinting=true but keep 120fps. It doesn't make a ton of sense to me limiting the engine to 60 fps, as my phone will appear less unique anyway since it will go as low as 24Hz, hence limiting Firefox to 24fps as well, since this implementation seems to limit Fx to 60fps only, rather than requesting the device to use 60Hz constantly.

[Mugurell]

I don't have a recent Samsung device now to test but looked again on a OnePlus supporting a 90 Hz refresh rate while having privacy.resistFingerprinting as both false and then true.
Both by using this steps - #20630 (comment) and by visiting testUfo.com I still get 90 Hz on Release and 60 Hz on Nightly.

It could be that Samsung added an exemption for org.mozilla.fenix also.
@slashdragos Curious if you could try entering adb shell dumpsys display | grep -A 16 DisplayModeDirector in terminal and checking what the reported values from PRIORITY_APP_REQUEST_REFRESH_RATE are when browsing. With or without the privacy.resistFingerprinting setting.

[slashdragos]

PRIORITY_APP_REQUEST_REFRESH_RATE_RANGE -> Vote{width=-1, height=-1, minRefreshRate=60.0, maxRefreshRate=Infinity, disableRefreshRateSwitching=false, baseModeRefreshRate=0.0} mModeSwitchingType: SWITCHING_TYPE_WITHIN_GROUPS mAlwaysRespectAppRequest: false SettingObserver mRefreshRateMode: REFRESH_RATE_MODE_SEAMLESS

I get the exact same result regardless of privacy.resistFingerprinting state. I should also point out that I have tried the latest Nightly x64 on Windows LTSC, running on a 360Hz display, and privacy.resistFingerprinting=true limits the Windows version as well to 60fps. This is definitely an intended behaviour by the developers, although I wish I could have both privacy.resistFingerprinting=true and high framerate.

[Mugurell]

Thank you for double checking this.
Reopening this ticket to have QA test if Samsung did recently change to remove limitations for org.mozilla.fenix also.

Curious on what's the max FPS on various Samsung devices for all 3 releases.
With and without privacy.resistFingerprinting enabled.
gfx.webrender.debug.profiler can be enabled in about:config for a reliable way of checking this.

[mcomella]

Performance triage: this sounds like 1) a functional decision regarding resistFingerprinting and 2) potentially a functional issue with certain devices and the view we draw web content into so we're removing the performance label. Please add the label again if further investigation finds a performance problem – thanks! 😁