ui: unified theme selector with seasonal scene packs + animated scenes (C3X + C4)

[ghbarker]

The evidence that motivated this

• Theme features had grown device-split and inconsistent: the 8-Bit Racer theme, wheel art, and colors each had their own toggles, and the comma four had no seasonal theming at all.
• The C3X theme dropdown had a real bug: the dialog callback read the DialogResult enum as if it were the selected label, so every selection saved "Off" regardless of what was highlighted.
• Adding a holiday look required code changes per theme — nothing a user could drop in.

Why the fix is shaped this way

• One selector, one param, both devices. BPThemePack picks the active pack; theme_pack.selector_entries() is the single source of truth the C3X page, the MICI page, and sunnylink all read — so the menus can never disagree. Packs are listed in calendar order of their season windows (Jan→Dec), with Off and 8-Bit Racer pinned first.
• Packs are asset-only. A theme is a directory (colors.json, wheel.png, sounds, scene.json, season.json) — bundled or dropped onto the device over SSH; no code per theme. BPThemeAutoSeasonal lets packs activate themselves inside their own declared date windows (fixed dates or movable feasts — Easter, Thanksgiving).
• One modular scene architecture (theme_scene.py): every renderer draws through a single active_scene() accessor, so there is no per-renderer theme logic to keep in sync; the animated layers (snow, string lights, bats, the NYE ball drop) are procedural — zero image assets for scenery.
• The C3X selector callback now follows the same DialogResult pattern as every other dialog in the file.

The evidence afterwards

• 25 theme tests green: every bundled pack's scene parses and renders, and every season window resolves (including the anchored movable feasts).
• The selector fix verified against the widget contract; MICI shares the same entries list, so both devices show the identical, calendar-ordered menu.

What each change is

• selfdrive/ui/bp/lib/theme_pack.py: pack discovery, season windows, calendar-ordered selector_entries().
• selfdrive/ui/bp/lib/theme_scene.py + renderer hookups (both devices): the scene architecture.
• selfdrive/assets/bp_themes/: eleven packs, each with colors, wheel art, scene, season window.
• Settings pages (C3X + MICI) + sunnylink: the unified Theme selector and Auto Seasonal toggle; the C3X dialog-callback fix.
• selfdrive/ui/soundd.py: per-pack sound overrides.

Test it yourself

• Settings → visuals: pick a pack and watch the onroad scene, colors, and wheel change live (no restart); toggle Auto Seasonal and the active pack follows the date.
• .

Risks / limits

• Default is no pack selected → stock look; nothing changes until you pick one. Opt-in, UI-only; no effect on control.
• Assets are stored directly in git (.gitattributes opts bp_themes/** out of LFS).

Screenshots

Captured on the PC preview (replay of a real drive, Minimal Driving View). Theme switching is live — no restart between these. Everything you see beyond the road — the falling snow, string lights, garlands, leaves, bats, the pumpkin — is procedural: zero image assets in the diff.

Halloween

Christmas

8-Bit Racer (same selector)

New Year's	Valentine's
St. Patrick's	April Fools
Easter	Cinco de Mayo
Fourth of July	Thanksgiving

comma four (MICI) layout