Domain:
- AppearanceSettings gains translucency_pct (u8, 0..=100, default 40)
with a clamping setter and serde round-trip coverage.
- DEFAULT_TRANSLUCENCY_PCT and MAX_TRANSLUCENCY_PCT exported for the
shell.
Core:
- BrowserCore::set_translucency_pct delegates to the appearance struct;
the existing reset_appearance covers the reset path.
- Integration test covers persistence into snapshot.appearance.
Render:
- chrome::sidebar::panel_bg(snapshot) replaces the static PANEL_BG
constant, mapping the user's translucency_pct linearly into the alpha
byte 0xff..0xb3. Sidebar (expanded + compact) and main pane consume
the helper so changing the setting at runtime updates every glass
surface in lock-step.
Form:
- Translucency row in chrome::appearance_form mirrors the design's
static track + thumb visual driven by the persisted percentage, plus
three preset chips (Solid 0 / Default 40 / Glassy 75) that mutate the
setting through shell.set_translucency_pct.
Strict UX rule preserved: alpha never drops below 0xb3 so panels stay
readable without backdrop blur (which GPUI 0.2.2 doesn't expose).
BrowserCore now owns an AppearanceSettings, exposes it through
BrowserSnapshot.appearance, and offers set_wallpaper_theme,
set_theme_mode, set_reduce_motion, reset_appearance mutators. Defaults
match the domain defaults (Dawn / System / motion-on) so existing
behaviour is unchanged for callers who don't touch appearance.
Integration tests cover initial snapshot defaults, mutation persistence
across snapshots, and reset behaviour.
ZacharyZhang-NY