Padding between pinned and unpinned tabs is visible again

[filips123]

Describe the bug

Since a few days on Nightly, padding between last pinned tab and the first unpinned one is again larger and more noticeable.

Expected behavior

Padding should be smaller/not noticeable, like it was before.

Screenshots

OS

Windows 10

OS - Others

No response

Firefox Version

116.0a1 (20230609214634)

Distribution

• [ ] Original Lepton
• [ ] Lepton's photon style
• [X] Lepton's proton style

Theme

• [ ] Light
• [X] Dark
• [ ] Alpenglow (System: Light)
• [ ] Alpenglow (System: Dark)
• [ ] System Default
• [ ] Others: (e.g. Photon Colors, Google Chrome Dark, Fairytale Of Nature)

Theme - More Info

No response

user.js setup

user.js setup

``` userChrome.compatibility.os true userChrome.compatibility.theme true userChrome.decoration.animate true userChrome.decoration.cursor true userChrome.decoration.download_panel true userChrome.decoration.field_border true userChrome.fullscreen.overlap true userChrome.fullscreen.show_bookmarkbar true userChrome.icon.context_menu true userChrome.icon.global_menu true userChrome.icon.global_menubar true userChrome.icon.library true userChrome.icon.menu true userChrome.icon.panel true userChrome.icon.panel_full true userChrome.icon.panel_photon false userChrome.icon.panel_sparse false userChrome.padding.bookmark_menu false userChrome.padding.bookmarkbar false userChrome.padding.global_menubar false userChrome.padding.infobar true userChrome.padding.menu false userChrome.padding.navbar_width true userChrome.padding.panel false userChrome.padding.popup_panel true userChrome.padding.tabbar_height true userChrome.padding.tabbar_width true userChrome.padding.toolbar_button true userChrome.padding.urlbar false userChrome.rounding.square_tab false userChrome.tab.bar_separator false userChrome.tab.bottom_rounded_corner false userChrome.tab.box_shadow false userChrome.tab.close_button_at_hover true userChrome.tab.color_like_toolbar false userChrome.tab.connect_to_window false userChrome.tab.container true userChrome.tab.crashed true userChrome.tab.dynamic_separator true userChrome.tab.dynamic_separtor true userChrome.tab.lepton_like_padding false userChrome.tab.letters_cleary true userChrome.tab.multi_selected true userChrome.tab.newtab_button_like_tab false userChrome.tab.newtab_button_proton true userChrome.tab.newtab_button_smaller false userChrome.tab.photon_like_contextline false userChrome.tab.photon_like_padding false userChrome.tab.pip true userChrome.tab.sound_hide_label true userChrome.tab.sound_with_favicons true userChrome.tab.static_separator false userChrome.tab.static_separator.selected_accent false userChrome.tab.unloaded true userChrome.tabbar.as_titlebar false userChrome.theme.built_in_contrast true userChrome.theme.fully_color true userChrome.theme.fully_dark true userChrome.theme.proton_chrome true userChrome.theme.proton_color true userChrome.theme.system_default true ```

Additional context

This is probably because of a change in recent Firefox Nightly that replaced [first-visible-unpinned-tab] selector with :nth-child, so CSS does not match the correct tab anymore. So, everything that references first-visible-unpinned-tab needs to be changed to use :nth-child. There probably also needs to be some additional work to keep it compatible with current stable release which still uses the original selector.

[black7375]

It hasn't been distributed in my nightly yet, so I'll test it and commit it after it's reproduced.

[black7375]

I applied a commit !! Thank you for the detailed report.