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
• Lepton's proton style

Theme

• Light
• 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.