update-launcher-icon

name	update-launcher-icon
description	Use when /logo.svg changes or when asked to update, replace, or apply the Android launcher app icon in femto-car-launcher. Triggers on "update the app icon", "apply the new logo", "make logo.svg the launcher icon". Covers deriving the adaptive-icon background / foreground / monochrome VectorDrawables from logo.svg, including the 66/108 safe-zone scaling math that raw SVG coordinates always violate.
allowed-tools	["Read","Write","Edit","Bash","Glob","Skill"]
paths	["logo.svg","app/src/main/res/drawable/ic_launcher_background.xml","app/src/main/res/drawable/ic_launcher_foreground.xml","app/src/main/res/mipmap-anydpi/**"]

Updating the launcher icon from logo.svg

/logo.svg (512×512, project root) is the brand-mark SSOT. The launcher icon is an adaptive icon derived from it; never edit the derived drawables as the design source — change logo.svg first, then re-run this procedure.

Layer mapping

logo.svg element	Android resource	Rule
Full-bleed background <rect>	drawable/ic_launcher_background.xml	Full-canvas fill of the rect's colour only. Drop the corner radius — the launcher applies its own mask shape.
Everything else (the mark)	drawable/ic_launcher_foreground.xml	Scaled into the safe zone (math below), centred on the canvas.
(same paths)	<monochrome> in mipmap-anydpi/*.xml	Shares the foreground drawable. Opacity differences survive as alpha in themed icons.

mipmap-anydpi/ic_launcher.xml and ic_launcher_round.xml only reference the two drawables — they normally need no edit.

Safe-zone scaling (the step everyone skips)

The adaptive-icon safe zone is the centre circle of diameter 66 on the 108 canvas. Copying logo.svg coordinates 1:1 into the foreground is always wrong — the full-bleed logo art reaches the canvas edge and the launcher mask clips it.

Keep the foreground viewport at 512 (matching logo.svg) and shrink the mark into the safe circle:

1. Safe radius in 512 units: 512 × 33 / 108 ≈ 156.
2. Find the mark's farthest extent from its own centre c, including stroke: r_max = max(|p − c|) + strokeWidth / 2 over all path end/corner points p.
3. scale = 150 / r_max (use ~150, not 156, for breathing room).
4. Transform every coordinate p' = 256 + (p − c) × scale and multiply every strokeWidth by the same scale. This also re-centres the mark's optical centre on (256, 256).
5. Re-verify after transforming (arithmetic slips here are common): recompute r'_max = max(|p' − (256, 256)|) + strokeWidth' / 2 over the transformed points with a calculator/script — do not do the square roots in your head. The procedure is only complete when r'_max ≤ 156.

Procedure

1. Read /logo.svg and classify elements per the layer-mapping table.
2. Write the background: 108 viewport, single M0,0h108v108h-108z path filled with the logo's background colour. Nothing else.
3. Write the foreground: 512 viewport, one <path> per SVG element, coordinates transformed by the safe-zone math. Attribute translation: stroke → android:strokeColor, stroke-width → android:strokeWidth, opacity on a stroked path → android:strokeAlpha (on a filled path → android:fillAlpha), stroke-linecap/-linejoin → android:strokeLineCap/LineJoin, no fill → android:fillColor="#00000000".
4. Monochrome: keep sharing the foreground drawable. Create a dedicated white-stroke drawable only if the mark encodes its hierarchy in colour rather than opacity (alpha is all the themed-icon pipeline keeps).
5. No rasters: minSdk = 33, so mipmap-anydpi always wins. Do not generate mipmap-*dpi webp/png fallbacks; delete any that exist.
6. Verify with the verify-android-build skill.

Skill-specific anti-patterns

• Copying logo.svg coordinates or stroke widths 1:1 into the foreground — the mask clips the mark (see safe-zone math).
• Reproducing the logo's rounded corners in the background layer.
• Generating density-bucket PNG/webp fallbacks "for older devices".
• Editing ic_launcher_foreground.xml directly to change the design — logo.svg is the SSOT.