| 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:
- Safe radius in 512 units:
512 × 33 / 108 ≈ 156.
- 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.
scale = 150 / r_max (use ~150, not 156, for breathing room).- 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).
- 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
- Read
/logo.svg and classify elements per the layer-mapping
table.
- Write the background: 108 viewport, single
M0,0h108v108h-108z path filled with the logo's background
colour. Nothing else.
- 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".
- 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).
- No rasters:
minSdk = 33, so mipmap-anydpi always wins.
Do not generate mipmap-*dpi webp/png fallbacks; delete any
that exist.
- 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.
