1932907 - Expose a pref for translucency for macOS system theme in FeatureManifest for Nimbus

Status: NEW

(Firefox :: Sidebar, task, P2)

Description

[Yulia Popova]

After discussing with Jane, Aaron, Emanuela, and Ania, we have agreed to enable the translucency effect for the system theme on macOS users in the Nightly build by default. However, we also need to introduce a toggle in Firefox Labs that will allow users to easily switch the effect on and off. This control in Labs will serve as a temporary solution until a permanent location for this setting is added on the new settings page.

Additionally, we will need to include a note about this change in the release notes.

Comment 1

[Ania]

Unfortunately, Labs don't allow pre-checking the feature checkbox ON by default. An alternative to adding translucency in Labs would be a very gradual Nimbus rollout of translucency. Start at, say, 10%, and then bump the rollout 10% every few days while monitoring feedback.

To do this, let's please add a new Nimbus feature, e.g., "styling" that would consolidate visual improvements and add a pref that governs the macOS translucency to it, similar to how the chatbot feature adds its prefs - https://searchfox.org/mozilla-central/source/toolkit/components/nimbus/FeatureManifest.yaml#3967

This approach is preferable to adding a variable to a feature as it allows us to avoid reverting users to the pre-experiment experience after the experiment or rollout ends.

Comment 2

[Ania]

We confirmed with Jane that rollout is an acceptable approach, so we can proceed with this work.

Comment 3

[Stuart Colville [:muffinresearch]]

Noting here that the conditions to enable translucency today are by setting the following prefs to true:

• widget.macos.titlebar-blend-mode.behind-window
• widget.macos.sidebar-blend-mode.behind-window
• browser.theme.native-theme

This also requires enabling the System theme - Auto theme.

If we want to toggle all of this with a single checkbox, what should happen to the theme when this turned off?

In about:addons, the previously used non-system theme is not restored if you disable it, though with other themes what happens is the system theme seems to be enabled (the system theme itself doesn't have the option to be disabled like other themes which is probably because it is the fallback so that wouldn't make sense).

Because of this the simplest solution here would be to ignore the theme aspect when disabling translucency, but it's important to note that wouldn't restore the theme you had before.

Comment 4

[Emilio Cobos Álvarez [:emilio]]

widget.macos.sidebar-blend-mode.behind-window

This one is not needed fwiw

Comment 5

[Sarah Clements [:sclements]]

Need info'ing Ania on design system status re native theme and priority, noting that we might have sidebar tweaks we'd need to fix before enabling this by default.