1865782 - general.smoothScroll from global preferences

Status: UNCONFIRMED

(Core :: Layout: Scrolling and Overflow, defect, P3)

Description

[Christian Hesse]

User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:120.0) Gecko/20100101 Firefox/120.0

Steps to reproduce:

I have a file /usr/lib/firefox/browser/defaults/preferences/prefs.js that gives some global preferences. This includes:

pref("general.smoothScroll", false);

This is (no longer) honored. It used to, but no idea when it broke.

Setting general.smoothScroll to FALSE in about:config works as expected.

Actual results:

Smooth scrolling is enabled.

Expected results:

Smooth scrolling should be disabled, as configured globally.

Comment 1

[Timothy Nikkel (:tnikkel)]

Maybe bug 1856196?

Comment 2

[Christian Hesse]

Hmm, bug 1856196 is supposed to be fixed in 120.0, no?
Then no, as it still happens there.

Comment 3

[Christian Hesse]

Just did some downgrades... This used to work ok with Firefox 113.0, and broke with Firefox 114.0. So the malfunction was introduces in between these two versions.

Comment 4

[Timothy Nikkel (:tnikkel)]

You could use mozregression https://mozilla.github.io/mozregression/ to find the exact changeset that caused it?

Comment 5

[Christian Hesse]

Sure... But one (hopefully not too) stupid question: Where do these builds read system configuration, specifically the file mentioned above?

Comment 6

[BugBot [:suhaib / :marco/ :calixte]]

The severity field is not set for this bug.
:hiro, could you have a look please?

For more information, please visit BugBot documentation.

Comment 7

[Hiroyuki Ikezoe (:hiro)]

Probably bug 1830103, it's uplifted to 114 beta, or bug 1753565. CCing Dan.

Comment 8

[Botond Ballo [:botond]]

(In reply to Christian Hesse from comment #5)

Sure... But one (hopefully not too) stupid question: Where do these builds read system configuration, specifically the file mentioned above?

That's a very good question. When mozregression runs a build, it extracts the application to a temporary directory such as /tmp/tmpyrw5hq58/firefox. The equivalent of /usr/lib/firefox/browser/defaults/preferences/prefs.js would then be /tmp/tmpyrw5hq58/firefox/browser/defaults/preferences/prefs.js (the defaults and preferences subdirectories may have to be created manually).

A challenge with testing this sort of scenario with mozregression is that it doesn't give you a chance to put a file there in between creating the temporary directory, and launching the application.

Anyways, there should be no need to run mozregression at this point since we have a couple of likely candidates for the regressing change already in comment 7.

Comment 9

[Botond Ballo [:botond]]

I tried adding a preference to browser/defaults/preferences/prefs.js, and about:config shows the value specified there as the preference's default value.

So, it was definitely bug 1753565 which changed the behaviour.

The intent of that change is to override a default value of general.smoothScroll=true with general.smoothScroll=false if the operating system "prefer reduced motion" setting is enabled, but respect a user-specified value of generalsmoothScroll=true.

Since the value in browser/defaults/preferences/prefs.js is being picked up as a default value rather than a user-specified value, the overriding happens.

Comment 10

[BugBot [:suhaib / :marco/ :calixte]]

:dlrobertson, since you are the author of the regressor, bug 1753565, could you take a look?

For more information, please visit BugBot documentation.

Comment 11

[Botond Ballo [:botond]]

Canceling the needinfo since we understand how bug 1753565 caused the regression.

A fix here would likely require new functionality in the Preferences API, to distinguish between a "hard-coded default" and a "default set via a prefs.js file".