fix(colours): chrome legibility audit — tab titles, findbar, address bar, unfocused window, and the downloads panel

[adamXbot]

Measured every visible text node in the chrome against its real background on Firefox 153, and separately ran the same window with an empty userChrome.css so any surface whose colour came back byte-identical is one the theme never touched. This is what that turned up, plus the downloads panel, which had no colour rules of its own.

All numbers are contrast ratios measured in the browser, with a dark palette (Monokai Pro / Nord) and the desktop in light mode — the case that exposes light-dark().

The recurring cause

Firefox declares colours on the descendant — .tab-content from --tab-selected-textcolor, .checkbox-label in the findbar. An element's own declaration beats an inherited value whatever its origin or importance, so tab { color: … !important } never reached the label. Add light-dark() resolving against the system scheme while the palettes in custom/ are unconditional, and a dark palette on a light desktop rendered them near-black on dark.

The fix is always the token or the descendant, never the ancestor.

Fixed

	before	after
Selected tab title	1.1:1	13.8:1
Findbar checkbox labels	1.3:1	fixed
Address-bar match highlight	2.3:1	8.9:1
Panel secondary text	3.0:1	7.5:1
Unfocused tab titles (22 palettes)	median 3.2:1, ten below 3:1	median 5.6:1, none below 3:1

Plus three variables that were used but never defined anywhere in the tree, so their declarations were dropped as invalid: --whitesur-button-hover-color and --whitesur-button-active-color (the findbar close button had no hover or press state at all) and --gnome-entry-border-color (a border that never drew).

And the surfaces the palette wasn't reaching: the address-bar results dropdown (#e0e0e6 row and a white "Search with Google" chip on a dark dropdown), and #browser / .browserContainer still holding #f9f9fb.

The downloads panel

parts/panels.css gives every arrow panel the popover surface, but none of the downloads panel's own furniture comes from the panel variables. The progress bar drew Firefox blue under every palette (paused drew GrayText, a system colour), and the blocked/insecure states are light-dark() pairs.

The blocked reds and ambers stay red and amber — that is the message — but are mixed toward --whitesur-ink so they follow the surface. The weights (55%, 45% under -i) come from computing WCAG ratios across all 22 palettes; the binding cases are Catppuccin Latte, whose ink is a soft slate rather than near-black, and Nord, the lightest of the dark surfaces.

How it was checked

Firefox 153.0.4, driven through Marionette, panels opened from chrome context and captured with OS-level screenshots — drawWindow cannot see an arrow panel. Every fix was measured before and after against the same session with the sheet removed.

Two cautions worth recording, both of which produced wrong answers before being caught:

• A DOM audit that composites ancestor backgrounds is wrong wherever Firefox paints from a sibling — a tab's .tab-background sits beside the label's container, not above it. Two of four initial findings did not survive being cropped out of a real screenshot, and one real finding was under-reported (2.8:1 by DOM, 2.3:1 by pixels). Every number above is pixel-confirmed.
• :-moz-window-inactive never matches while Marionette is attached, because the remote agent keeps Services.focus.activeWindow set. Anything focus-dependent has to be tested with a plain launch and --no-remote.

After these changes the audit reports no text below 4.5:1 and no unthemed surfaces (was five).

Not included

The -a highlight-tab option is a separate PR, since it is the only user-facing new flag here.

[github-actions]

Theme preview

Rendered from 394eff3 against the base branch.

Linux — 22 views changed

Customize mode (0.04% of pixels)

Find bar — light (0.14% of pixels)

Variant: increase-contrast (0.00% of pixels)

Variant: theme-ayu-mirage (0.10% of pixels)

Variant: theme-catppuccin-frappe (0.10% of pixels)

Variant: theme-catppuccin-latte (0.06% of pixels)

Variant: theme-catppuccin-macchiato (0.10% of pixels)

Variant: theme-catppuccin-mocha (0.11% of pixels)

Variant: theme-dracula (0.11% of pixels)

Variant: theme-everforest-dark (0.10% of pixels)

Variant: theme-github-dark (0.10% of pixels)

Variant: theme-gruvbox-dark (0.10% of pixels)

Variant: theme-material-ocean (0.10% of pixels)

Variant: theme-material-palenight (0.11% of pixels)

Variant: theme-monokai-pro (0.11% of pixels)

Variant: theme-night-owl (0.10% of pixels)

Variant: theme-nord (0.11% of pixels)

Variant: theme-one-dark (0.10% of pixels)

Variant: theme-rose-pine (0.10% of pixels)

Variant: theme-solarized-dark (0.09% of pixels)

Variant: theme-solarized-light (0.07% of pixels)

Variant: theme-tokyonight (0.10% of pixels)

macOS — 43 views changed

Browser window — dark (0.01% of pixels)

Tab playing audio (0.01% of pixels)

Tab muted (0.01% of pixels)

Container tabs (0.01% of pixels)

Tab strip overflowing (0.00% of pixels)

Compact density (0.00% of pixels)

Sidebar — bookmarks (0.00% of pixels)

Sidebar — history (0.00% of pixels)

Right-to-left UI (0.01% of pixels)

Customize mode (0.06% of pixels)

Vertical tabs (0.01% of pixels)

Customised toolbar (0.01% of pixels)

Browser window — light (0.01% of pixels)

Address bar focused — light (0.16% of pixels)

Find bar — light (0.18% of pixels)

Variant: compact-tabs (0.01% of pixels)

Variant: enabletabview (0.01% of pixels)

Variant: hideextension (0.01% of pixels)

Variant: noidentity (0.01% of pixels)

Variant: singletabhidden (0.01% of pixels)

Variant: standard-urlbar (0.01% of pixels)

Variant: tabs-swapclose (0.01% of pixels)

Variant: theme-ayu-mirage (0.08% of pixels)

Variant: theme-catppuccin-frappe (0.08% of pixels)

Variant: theme-catppuccin-latte (0.05% of pixels)

Variant: theme-catppuccin-macchiato (0.08% of pixels)

Variant: theme-catppuccin-mocha (0.08% of pixels)

Variant: theme-dracula (0.08% of pixels)

Variant: theme-everforest-dark (0.08% of pixels)

Variant: theme-github-dark (0.08% of pixels)

Variant: theme-gruvbox-dark (0.08% of pixels)

Variant: theme-gruvbox-light (0.02% of pixels)

Variant: theme-material-ocean (0.08% of pixels)

Variant: theme-material-palenight (0.08% of pixels)

Variant: theme-monokai-pro (0.08% of pixels)

Variant: theme-night-owl (0.08% of pixels)

Variant: theme-nord (0.08% of pixels)

Variant: theme-one-dark (0.07% of pixels)

Variant: theme-rose-pine (0.08% of pixels)

Variant: theme-solarized-dark (0.07% of pixels)

Variant: theme-solarized-light (0.05% of pixels)

Variant: theme-tokyonight (0.08% of pixels)

Variant: windows-swapclose (0.01% of pixels)

Windows — 43 views changed

Browser window — dark (0.01% of pixels)

Tab playing audio (0.00% of pixels)

Tab muted (0.01% of pixels)

Container tabs (0.01% of pixels)

Tab strip overflowing (0.00% of pixels)

Compact density (0.00% of pixels)

Sidebar — bookmarks (0.00% of pixels)

Sidebar — history (0.00% of pixels)

Right-to-left UI (0.01% of pixels)

Customize mode (0.06% of pixels)

Vertical tabs (0.01% of pixels)

Customised toolbar (0.01% of pixels)

Browser window — light (0.01% of pixels)

Address bar focused — light (0.17% of pixels)

Find bar — light (0.19% of pixels)

Variant: compact-tabs (0.01% of pixels)

Variant: enabletabview (0.01% of pixels)

Variant: hideextension (0.01% of pixels)

Variant: noidentity (0.01% of pixels)

Variant: singletabhidden (0.01% of pixels)

Variant: standard-urlbar (0.01% of pixels)

Variant: tabs-swapclose (0.01% of pixels)

Variant: theme-ayu-mirage (0.08% of pixels)

Variant: theme-catppuccin-frappe (0.09% of pixels)

Variant: theme-catppuccin-latte (0.05% of pixels)

Variant: theme-catppuccin-macchiato (0.09% of pixels)

Variant: theme-catppuccin-mocha (0.09% of pixels)

Variant: theme-dracula (0.09% of pixels)

Variant: theme-everforest-dark (0.09% of pixels)

Variant: theme-github-dark (0.08% of pixels)

Variant: theme-gruvbox-dark (0.09% of pixels)

Variant: theme-gruvbox-light (0.02% of pixels)

Variant: theme-material-ocean (0.09% of pixels)

Variant: theme-material-palenight (0.09% of pixels)

Variant: theme-monokai-pro (0.09% of pixels)

Variant: theme-night-owl (0.09% of pixels)

Variant: theme-nord (0.09% of pixels)

Variant: theme-one-dark (0.08% of pixels)

Variant: theme-rose-pine (0.09% of pixels)

Variant: theme-solarized-dark (0.07% of pixels)

Variant: theme-solarized-light (0.06% of pixels)

Variant: theme-tokyonight (0.09% of pixels)

Variant: windows-swapclose (0.01% of pixels)

_{Views: browser window, focused address bar, find bar — each in light and dark. Native popups (app menu, context menus) are OS-level windows and cannot be captured. Workflow run}