Affected versions

• 88.0a1 (20210226094123)

Affected platforms

• Windows 10x64
• macOS 11.2
• Ubuntu 20

Steps to reproduce

1. Open Firefox with a new profile and click on the Home, Library, and Sidebar buttons.
2. Restart Firefox with toolbar enabled.
3. Acces Customize mode.
4. Click on the Restore Defaults button.

Expected result

• The Library, Sidebar, and Home buttons are still on the toolbar.

Actual result

• The used buttons are removed from the toolbar.

Notes

• Attached a screen recording: link.

This happens with home button when a custom url is set as well. The home button is shown in toolbar, but by clicking on restore in customize page will get it back in the list.

So I think we need a product decision here.

Right now CustomizableUI has a fixed idea of a set of buttons that belong in each toolbar. With the proton prefs on, the home/library/sidebar buttons are no longer in that set. This is what governs both the idea it has about whether we are in the "default state" (ie whether the actual toolbar state matches the defaults) and if we're not, what happens if you click the "restore defaults" button (which restores that default state).

We've not had a dynamic default state before, because it gets a bit messy.

Whatever we decide, we should probably update CustomizableUI's inDefaultState getter as well as the reset method to do the right thing, and add a test.

:mstriemer, can you raise this with product?

The new expected result should be that restoring default will set the new default, therefore I suggest marking as WONT FIX:

• OK to have "Restore defaults" remove toolbar buttons that were retained for existing users of these features
• OK to have the home button appear if users set the home page and then disappear if users then Restore defaults (users who are in customize pane can then decide to add the home button back again if useful to them)