Fix linux theme change

[piotrsac]

No description provided.

[linear]

VOY-138 Auto Theme not working

Voyager theme set: Auto
When changed form Dark to Default on Debian 13 x86_64 Voyager is still dark

Review in Linear

[Copilot]

Pull request overview

This PR adjusts the app’s theme synchronization logic in the root layout to better handle OS theme changes on Linux (notably in Tauri), adding a more reliable re-probe flow and fallbacks.

Changes:

• Introduces autoMode() and refines when OS-driven theme updates should apply vs. when a user-selected theme should be respected.
• Updates the Tauri onThemeChanged handling to re-read the OS theme via the existing probe instead of trusting the event payload.
• Adds fallbacks to re-sync theme on media-query changes, focus, and visibility changes (Tauri-only).

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[piotrsac]

@claude review opus

[github-actions]

Claude finished @piotrsac's task in 4m 21s —— View job

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🦀 Review

Severity: 🔴 blocking · 🟡 should-fix · 🟢 nit

• 🔴 lib/voyager_web/components/layouts/root.html.heex:44 — nativeOs is inferred from sessionStorage/__VOYAGER_OS_THEME__, but both can hold a matchMedia-derived value (setOs persists every source, and seed_script falls back to matchMedia when the portal snapshot fails). After one reload in a browser, or on the first paint in Tauri with no working portal, nativeOs is true, the matchMedia change handler returns early, and auto theme stops following the OS. Flip nativeOs only on a value that really came from a native probe.
• 🟡 rel/app/src-tauri/src/theme.rs:94 — BASE_200_DARK is rgb(32, 36, 41), but the oklch(23.26% 0.014 253.1) it documents is rgb(25, 30, 36); the native fill is lighter than the page background it's meant to match.

<verdict: 1 blocking, 1 should-fix, 0 nits>
· piotrsaczawa/voy-138-auto-theme-not-working

[github-actions]

🔴 blocking: nativeOs is set from values that are not necessarily native. setOs writes every OS theme to sessionStorage — including ones derived from matchMedia — and seed_script always assigns __VOYAGER_OS_THEME__, falling back to matchMedia when the portal snapshot fails. So (a) in a plain browser, one OS theme change writes voyager:os-theme, and after the next reload nativeOs is true, the change listener on line 93 returns early, and auto theme stops following the OS for the rest of the session; (b) in Tauri on a desktop with no working settings portal, the seed hint is matchMedia-derived, nativeOs is true from the first paint and os_theme returns null, so the matchMedia fallback is dead and auto theme never updates — the exact VOY-138 symptom. Only flip nativeOs on a value that actually came from a native probe (e.g. a separate flag set by seed_script when the snapshot succeeded, plus setOsFromNative), and don't infer it from sessionStorage.

[github-actions]

🟡 should-fix: BASE_200_DARK doesn't match the token the doc comment above cites. oklch(23.26% 0.014 253.1) converts to rgb(25, 30, 36) (#191E24), not rgb(32, 36, 41) — the light constant checks out, so the dark one is the outlier. The native window fill is then visibly lighter than the page's dark base-200, which is the seam background_color/set_surface exist to remove.

Suggested change

	const BASE_200_DARK: tauri::window::Color = tauri::window::Color(32, 36, 41, 255);
	const BASE_200_DARK: tauri::window::Color = tauri::window::Color(25, 30, 36, 255);