android: the falcon on the launcher — a real adaptive icon, with the monochrome layer

The phone has been wearing tauri's logo. `tauri android init` writes the
generated project's `res/` from its own template and never reads
`src-tauri/icons/android/`, which has carried the falcon since 50afa6a, and the
detour build runs cargo and Gradle directly — so nothing ever copied it across:
the two dominant colours in the packaged `mipmap-xxxhdpi/ic_launcher.png` are
`#24c8db` and `#ffc131`, tauri's own brand cyan and amber. `src-tauri/android/res/`
is the app module's res now, tracked, and `build.sh` and `dev.sh` copy the whole
tree into `gen/android` before Gradle, because that project is regenerated and
gitignored and an asset that only lives there is an asset that disappears.

It is a real adaptive icon: the kit's foreground and its **monochrome** layer at
five densities, the legacy mipmaps under it, and the background as one
`#FF05080B` colour resource rather than five identical flat PNGs, so the gradient
being mocked separately replaces one file. The kit's own XML could not ship — it
points every layer at `@drawable/` while shipping them as PNGs under `mipmap-*`,
and in the generated project two of those three references resolve to Android
Studio's template robot rather than failing — so the overlay's XML says
`@mipmap/` and `@color/`, and its colour file takes the same name tauri's does,
because two files declaring one colour is a hard aapt2 error.

Losing the copy would be silent — the APK still builds, still installs, and wears
the old logo with nothing in the log — so `verify-icon.sh` opens every APK both
scripts make and reads the resources back out: the two `mipmap-anydpi-v26` XMLs
present, and four PNG names at five densities byte for byte from the overlay. A
release APK keeps neither the bytes nor the names — AGP re-encodes every PNG and
shortens every resource path — so that path asks `aapt2 dump resources` what each
name points at and compares pixel dimensions instead; 72×72 at hdpi still tells
the kit's icon from tauri's 49×49. No walk step: a launcher icon is not reachable
from inside the app, and the masking and the themed layer want a minute with the
phone's home screen.

ANDROID.md

@@ -30,6 +30,7 @@ implements is `research/mobile-mockup/` (gitignored; see its README).
 | `src-tauri/tauri.android.conf.json` | merged over `tauri.conf.json` on Android: one window at `mobile.html`, no desktop resources, `minSdkVersion` 26 |
 | `src-tauri/gen/android/` | the generated Gradle project (`npx tauri android init`); `minSdk = 26`. Gitignored |
 | `src-tauri/android/build.sh`, `deploy.sh` | the detour build (below) and build → install → launch → screenshot |
+| `src-tauri/android/res/` | the app module's own Android resources, tracked: the adaptive launcher icon, its monochrome layer, the legacy mipmaps and the one colour the background is. `build.sh` and `dev.sh` copy the whole tree into `gen/android/app/src/main/res/` before Gradle; `verify-icon.sh` reads it back out of the APK |
 | `src-tauri/src/android_glue.rs` | `JNI_OnLoad`: hands the JavaVM and app Context to `ndk-context` (cpal's AAudio backend needs it; tao 0.35 never fills it) |
 | `src-tauri/src/updater_mobile.rs` | the updater's stand-in on mobile (`#[cfg(mobile)] #[path]`) |
 | `src-tauri/src/lyric_align_stub.rs`, `vocal_sep_stub.rs` | stand-ins off Windows for the two Windows ML modules |
@@ -1284,6 +1285,8 @@ cargo build --lib -p app --target aarch64-linux-android --features tauri/custom-
 # 1. strip the library's debug info (607 MB → 50 MB; the debug packaging keeps symbols)
 cp target/aarch64-linux-android/debug/libapp_lib.so src-tauri/gen/android/app/src/main/jniLibs/arm64-v8a/
 "%LOCALAPPDATA%\Android\Sdk\ndk\28.2.13676358\toolchains\llvm\prebuilt\windows-x86_64\bin\llvm-strip.exe" --strip-debug src-tauri/gen/android/app/src/main/jniLibs/arm64-v8a/libapp_lib.so
+# 1b. the app's own resources, over the generated project's (the launcher icon)
+cp -r src-tauri/android/res/. src-tauri/gen/android/app/src/main/res/
 # 2. package with Gradle, skipping the task that would redo the symlink
 cd src-tauri/gen/android && ./gradlew.bat assembleArm64Debug -x rustBuildArm64Debug
 ```
@@ -1477,6 +1480,98 @@ A command that has been renamed answers `No command <name> found for plugin
 <class>`, which lands in logcat rather than on screen:
 `adb logcat --pid=$(adb shell pidof com.soulstream.app)`.
 
+## The launcher icon
+
+Until this round the phone wore **tauri's** logo. `tauri android init` writes
+the generated project's `res/` from its own template and never reads
+`src-tauri/icons/android/` — which has carried the falcon since `50afa6a`
+— and the detour build runs cargo and Gradle directly, so nothing ever
+copied it across. The two dominant colours in
+`gen/android/app/src/main/res/mipmap-xxxhdpi/ic_launcher.png` were `#24c8db`
+and `#ffc131`: tauri's brand cyan and tauri's brand amber.
+
+`src-tauri/android/res/` is the app module's res, tracked, and `build.sh` and
+`dev.sh` copy the whole tree into the generated project before Gradle runs.
+It carries:
+
+- `mipmap-anydpi-v26/ic_launcher.xml` and `ic_launcher_round.xml` — the
+  adaptive icon: a foreground, a background, and a **monochrome** layer, which
+  is what Android 13's themed icons need and what tauri's generator has never
+  made;
+- `mipmap-{m,h,xh,xxh,xxxh}dpi/` — `ic_launcher_foreground.png` and
+  `ic_launcher_monochrome.png` (108–432 px) from the kit's
+  `android/adaptive/res/`, and the legacy `ic_launcher.png` /
+  `ic_launcher_round.png` (48–192 px) from its `android/legacy/`;
+- `values/ic_launcher_background.xml` — `#FF05080B`, the brand's night.
+
+Three things about it are not obvious.
+
+**The kit's own adaptive XML does not compile here.** Its
+`android/adaptive/res/mipmap-anydpi-v26/*.xml` points every layer at
+`@drawable/…`, and the kit ships those layers as PNGs under `mipmap-*` with
+no `drawable-*` directory anywhere. That is worse than a missing resource:
+the generated project still carries Android Studio's template vectors at
+`drawable/ic_launcher_background.xml` and
+`drawable-v24/ic_launcher_foreground.xml`, so two of the three references
+resolve — to the green robot — and only `@drawable/ic_launcher_monochrome`
+fails the build. The overlay's XML says `@mipmap/` for the two image layers
+and `@color/` for the background instead.
+
+**The background is one colour resource, not five identical flat PNGs.**
+A richer gradient is being mocked separately; when it is approved it replaces
+one file, and the three XML references do not move.
+
+**The colour file is named `ic_launcher_background.xml` on purpose.**
+`src-tauri/icons/android/values/ic_launcher_background.xml` declares the same
+resource name (`#fff`), and two files in one `values/` directory declaring
+one colour is a hard aapt2 error — `resource 'color/ic_launcher_background'
+has a conflicting value`. Sharing the filename means the overlay overwrites
+it rather than colliding with it, if a future `npx tauri android init` ever
+copies it in.
+
+That leaves `src-tauri/icons/android/` a second, stale copy of these same
+resource names: white background, no monochrome, hdpi at 49×49. Nothing on
+Android reads it while the build is the detour — but `npx tauri icon` writes
+it, and it should be brought to the kit before anyone builds through the CLI.
+
+### Checking it
+
+`verify-icon.sh` opens the APK `build.sh` has just made and reads the
+resources back out. It checks the overlay's own two XMLs first, before the APK
+is opened — a `<monochrome>` layer that a later edit drops is a failure too —
+and then reads the APK, debug and release differently, because AGP hands them
+to aapt2 differently:
+
+- **debug** — the packaging default for a debuggable build type is
+  `--no-crunch`, so every entry *is* the file on disk. Both
+  `res/mipmap-anydpi-v26/*.xml` must be in the APK, and all four PNG names at
+  all five densities must be byte for byte the overlay's.
+- **release** (`--crunched`) — aapt2 re-encodes every PNG, *and* AGP's
+  resource optimization (`OptimizeResourcesTask` → `SHORTEN_RESOURCE_PATHS`)
+  renames the lot: an APK optimized here had no `res/mipmap-…` entry left at
+  all, only `res/Ag.png`. Neither the bytes nor the names survive, so the
+  check asks `aapt2 dump resources` what each name points at and compares the
+  pixel dimensions of whatever that is — 72×72 at hdpi still separates the
+  kit's legacy icon from tauri's 49×49. If the resource *names* have been
+  collapsed as well (that comes with resource shrinking, which this project
+  does not turn on), it says the icon is unchecked rather than claiming a
+  failure it cannot see.
+
+Both `build.sh` and `dev.sh` call it, so no APK this repo makes can quietly go
+back to the old artwork. It costs about a second and a half on the 107 MB
+debug APK.
+
+What it cannot check is what the icon looks like. `deploy.sh`'s `px-1.png` is
+a screenshot of the app five seconds after launch; the launcher is not in it.
+The one thing that may now differ there is the Android 12+ system splash,
+which is drawn from the launcher icon — if a cold start ever runs past those
+five seconds, that splash is the falcon on `#05080B` rather than tauri's mark.
+**Adaptive masking and the monochrome layer can only be judged from the
+phone's home screen**, which is a minute with the Pixel: the icon under the
+launcher's mask, in the app drawer, in recents and in another app's share
+sheet — and then Wallpaper & style → Themed icons on, to see the monochrome
+layer take the wallpaper's colour.
+
 ## Verifying
 
 ```bash

src-tauri/android/build.sh

@@ -51,6 +51,15 @@ mkdir -p "$DEST"
 cp "$SO" "$DEST/libapp_lib.so"
 "$BIN/llvm-strip.exe" --strip-debug "$DEST/libapp_lib.so"
 ls -la "$DEST/libapp_lib.so"
+# The launcher identity, into a project that cannot keep it: gen/android is
+# regenerated by the tauri CLI and gitignored, and the detour build never runs
+# that CLI, so the res it holds is still the one `android init` wrote — tauri's
+# own logo. Everything under src-tauri/android/res/ is copied over it on every
+# build. The whole tree, not a file list: a later round adding a resource adds
+# a file there and this line does not change.
+echo "== res overlay $(date +%T)"
+test -d src-tauri/android/res || { echo "src-tauri/android/res is gone — the APK would wear tauri's logo and say nothing"; exit 1; }
+cp -r src-tauri/android/res/. src-tauri/gen/android/app/src/main/res/
 echo "== gradle $(date +%T)"
 cd src-tauri/gen/android
 ./gradlew.bat assemble$VARIANT -x rustBuild$VARIANT -q 2>&1 | grep -v "^$" | tail -20 || true
@@ -82,4 +91,5 @@ else
     APK=src-tauri/gen/android/app/build/outputs/apk/arm64/debug/app-arm64-debug.apk
 fi
 ls -la "$APK"
+bash src-tauri/android/verify-icon.sh "$APK" $([ "$REL" = "1" ] && echo --crunched)
 echo "== done $(date +%T)"

src-tauri/android/dev.sh

@@ -33,11 +33,21 @@ DEST=src-tauri/gen/android/app/src/main/jniLibs/arm64-v8a
 mkdir -p "$DEST"
 cp "$SO" "$DEST/libapp_lib.so"
 "$BIN/llvm-strip.exe" --strip-debug "$DEST/libapp_lib.so"
+# The launcher identity, into a project that cannot keep it: gen/android is
+# regenerated by the tauri CLI and gitignored, and the detour build never runs
+# that CLI, so the res it holds is still the one `android init` wrote — tauri's
+# own logo. Everything under src-tauri/android/res/ is copied over it on every
+# build. The whole tree, not a file list: a later round adding a resource adds
+# a file there and this line does not change.
+echo "== res overlay $(date +%T)"
+test -d src-tauri/android/res || { echo "src-tauri/android/res is gone — the APK would wear tauri's logo and say nothing"; exit 1; }
+cp -r src-tauri/android/res/. src-tauri/gen/android/app/src/main/res/
 echo "== gradle $(date +%T)"
 cd src-tauri/gen/android
 ./gradlew.bat assembleArm64Debug -x rustBuildArm64Debug -q 2>&1 | grep -v "^$" | tail -20 || true
 cd /f/Coding/SoulStream
 APK=src-tauri/gen/android/app/build/outputs/apk/arm64/debug/app-arm64-debug.apk
+bash src-tauri/android/verify-icon.sh "$APK"
 echo "== install $(date +%T)"
 "$ADB" install -r "$APK" 2>&1 | tail -1
 "$ADB" shell pm grant com.soulstream.app android.permission.POST_NOTIFICATIONS 2>/dev/null || true

src-tauri/android/res/mipmap-anydpi-v26/ic_launcher.xml

@@ -0,0 +1,10 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- @mipmap, not the kit's @drawable: the layers ship as PNGs under
+     mipmap-*, and @drawable/ic_launcher_foreground still resolves to the
+     template robot in the generated project. The background is one colour
+     resource, so the gradient replaces one file when it is approved. -->
+<adaptive-icon xmlns:android="http://schemas.android.com/apk/res/android">
+    <background android:drawable="@color/ic_launcher_background" />
+    <foreground android:drawable="@mipmap/ic_launcher_foreground" />
+    <monochrome android:drawable="@mipmap/ic_launcher_monochrome" />
+</adaptive-icon>

src-tauri/android/res/mipmap-anydpi-v26/ic_launcher_round.xml

@@ -0,0 +1,10 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- @mipmap, not the kit's @drawable: the layers ship as PNGs under
+     mipmap-*, and @drawable/ic_launcher_foreground still resolves to the
+     template robot in the generated project. The background is one colour
+     resource, so the gradient replaces one file when it is approved. -->
+<adaptive-icon xmlns:android="http://schemas.android.com/apk/res/android">
+    <background android:drawable="@color/ic_launcher_background" />
+    <foreground android:drawable="@mipmap/ic_launcher_foreground" />
+    <monochrome android:drawable="@mipmap/ic_launcher_monochrome" />
+</adaptive-icon>

src-tauri/android/res/values/ic_launcher_background.xml

@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+    <!-- the brand's night; the whole adaptive background is this -->
+    <color name="ic_launcher_background">#FF05080B</color>
+</resources>

src-tauri/android/verify-icon.sh

@@ -0,0 +1,133 @@
+#!/usr/bin/env bash
+# Is the falcon actually in the APK? The way this loses is silent: gen/android
+# is regenerated and gitignored, so a project rebuilt without the overlay copy
+# still compiles, still installs, and wears tauri's logo again with nothing in
+# the log. So every APK this repo makes is opened and read before it is
+# installed. Called by build.sh and dev.sh; run it by hand on any APK.
+#
+#   bash src-tauri/android/verify-icon.sh <apk> [--crunched]
+#
+# Debug and release are read DIFFERENTLY, because AGP treats their resources
+# differently and both differences were measured on 2026-09-14:
+#
+#   debug    packaged with --no-crunch (AGP's default for the debuggable build
+#            type), so every entry is byte for byte the file on disk — checked
+#            against the real 107 MB APK. Names are names: res/mipmap-hdpi-v4/…
+#   release  --crunched. Two things change. aapt2 re-encodes every PNG, so the
+#            bytes are no longer the file; and AGP's resource optimization
+#            (OptimizeResourcesTask → SHORTEN_RESOURCE_PATHS) renames the lot
+#            to res/Ag.png, so the names are gone as well — an APK optimized
+#            here had zero entries matching "res/mipmap". Nothing but the
+#            resource table can say what is what, so that is what is read:
+#            `aapt2 dump resources`, then the pixel dimensions of whatever it
+#            points at. 72x72 at hdpi still tells the kit's legacy icon from
+#            tauri's 49x49.
+#
+# If anyone ever sets isCrunchPngs = true on the debug build type, the debug
+# path fails on byte-equality with the file named; --crunched is the answer.
+set -uo pipefail
+APK="${1:-}"
+test -n "$APK" || { echo "usage: verify-icon.sh <apk> [--crunched]"; exit 2; }
+# resolved before the cd, so a relative path typed by hand still means what it
+# said; the repo root is where $RES is
+[ -f "$APK" ] && APK="$(cd "$(dirname "$APK")" && pwd)/$(basename "$APK")"
+# the repo this script is IN, not a drive letter. build.sh and dev.sh have
+# already cd'd to /f/Coding/SoulStream and call this as
+# src-tauri/android/verify-icon.sh, so ../.. lands on the same place they are
+# — but a checkout on another letter, or an APK checked by hand from
+# somewhere else, then compares against ITS OWN overlay rather than F:'s.
+cd "$(dirname "$0")/../.." || { echo "cannot find the repo above $0"; exit 2; }
+CRUNCH=0; [ "${2:-}" = "--crunched" ] && CRUNCH=1
+RES=src-tauri/android/res
+DPI="mdpi hdpi xhdpi xxhdpi xxxhdpi"
+NAMES="ic_launcher ic_launcher_round ic_launcher_foreground ic_launcher_monochrome"
+bad() { echo "ICON CHECK FAILED: $*"; exit 1; }
+test -f "$APK" || bad "no APK at $APK"
+test -d "$RES" || bad "$RES is missing — there is nothing to check the APK against"
+
+# 1. the overlay itself, before the APK is opened. The monochrome layer is the
+#    one Android 13 tints for themed icons and the one tauri's generator has
+#    never made, so a later edit that drops it should not pass quietly.
+for x in ic_launcher ic_launcher_round; do
+    test -f "$RES/mipmap-anydpi-v26/$x.xml" || bad "$RES/mipmap-anydpi-v26/$x.xml is missing from the overlay"
+    grep -q "<monochrome" "$RES/mipmap-anydpi-v26/$x.xml" \
+        || bad "$RES/mipmap-anydpi-v26/$x.xml declares no <monochrome> layer — themed icons need one"
+done
+for d in $DPI; do for n in $NAMES; do
+    test -f "$RES/mipmap-$d/$n.png" || bad "$RES/mipmap-$d/$n.png is missing from the overlay"
+done; done
+
+# the PNG header's width and height, eight bytes at offset 16 — the one thing
+# about an image that survives being re-encoded. Printed as 72x72, so a failure
+# reads as a size rather than as hex.
+dims() {
+    local h
+    h="$(xxd -s 16 -l 8 -p)"
+    [ "${#h}" = 16 ] || { echo "unreadable"; return; }
+    printf '%dx%d\n' "$((16#${h:0:8}))" "$((16#${h:8:8}))"
+}
+
+LIST="$(unzip -l "$APK")" || bad "cannot read $APK"
+
+if [ "$CRUNCH" = 0 ]; then
+    # 2. debug: the adaptive XMLs by name, then all twenty PNGs byte for byte.
+    #    Nothing but the overlay makes a mipmap-anydpi-v26 file, so its absence
+    #    is exactly the failure this script exists for.
+    for x in ic_launcher ic_launcher_round; do
+        echo "$LIST" | grep -q " res/mipmap-anydpi-v26/$x\.xml$" \
+            || bad "res/mipmap-anydpi-v26/$x.xml is not in the APK — $RES never reached src-tauri/gen/android/app/src/main/res"
+    done
+    for d in $DPI; do for n in $NAMES; do
+        got="res/mipmap-$d-v4/$n.png"
+        echo "$LIST" | grep -q " $got$" || bad "$got is not in the APK"
+        unzip -p "$APK" "$got" | cmp -s - "$RES/mipmap-$d/$n.png" \
+            || bad "$got in the APK is not $RES/mipmap-$d/$n.png — a stale res in gen/, the overlay lost a file, or this build crunched its PNGs (then: --crunched)"
+    done; done
+    echo "== icon: adaptive + monochrome, five densities, byte for byte from $RES"
+    exit 0
+fi
+
+# 3. release. Ask the resource table what the names point at, since the paths
+#    have very likely been shortened away. aapt2 is beside the zipalign and
+#    apksigner build.sh has just used.
+SDKU=""
+[ -n "${ANDROID_HOME:-}" ] && SDKU="$(cygpath -u "$ANDROID_HOME" 2>/dev/null || echo "")"
+[ -z "$SDKU" ] && [ -n "${LOCALAPPDATA:-}" ] && SDKU="$(cygpath -u "$LOCALAPPDATA" 2>/dev/null || echo "")/Android/Sdk"
+A2="$(ls -1 "$SDKU"/build-tools/*/aapt2.exe 2>/dev/null | sort -V | tail -1 || true)"
+if [ -z "$A2" ]; then
+    echo "== icon: NOT CHECKED — no aapt2 under ${SDKU:-(no SDK path)}/build-tools."
+    echo "   A release APK's resource paths are shortened (res/Ag.png), so names"
+    echo "   alone cannot find the icon. Unverified here, not missing."
+    exit 0
+fi
+# one line per file entry: "<name> <config> <path in the APK>"
+MAP="$("$A2" dump resources "$APK" | awk '
+    /^[ \t]*resource 0x[0-9a-f]+ mipmap\// { split($3, a, "/"); cur = a[2]; next }
+    /^[ \t]*resource 0x/ { cur = ""; next }
+    cur != "" { for (i = 1; i <= NF; i++) if ($i ~ /^res\//) { cfg = $1; gsub(/[()]/, "", cfg); print cur, cfg, $i } }
+')" || bad "aapt2 could not read the resource table of $APK"
+# the other half of the same optimization pass: with resource shrinking on,
+# aapt2 also collapses the NAMES, and then even the table cannot say which
+# entry is the launcher icon
+if echo "$MAP" | grep -q "0_resource_name_obfuscated"; then
+    echo "== icon: NOT CHECKED — this APK's resource names are collapsed"
+    echo "   (aapt2 optimize --collapse-resource-names, which comes with resource"
+    echo "   shrinking). Nothing left to match on. Unverified here, not missing."
+    exit 0
+fi
+# the config is printed as "mdpi" or as "mdpi-v4" depending on the link's
+# min-sdk — both seen on this machine from the same resource tree, so both are
+# taken, and "anydpi" matches the "anydpi-v26" the adaptive icon lives in
+look() { echo "$MAP" | awk -v n="$1" -v c="$2" '$1 == n && ($2 == c || $2 ~ "^" c "-v[0-9]+$") { print $3; exit }'; }
+for x in ic_launcher ic_launcher_round; do
+    got="$(look "$x" anydpi)"
+    test -n "$got" || bad "mipmap/$x has no anydpi entry in this APK — the adaptive icon is not in it, so $RES never reached src-tauri/gen/android/app/src/main/res"
+done
+for d in $DPI; do for n in $NAMES; do
+    got="$(look "$n" "$d")"
+    test -n "$got" || bad "mipmap/$n has no $d entry in this APK"
+    a="$(unzip -p "$APK" "$got" | dims)"
+    b="$(dims < "$RES/mipmap-$d/$n.png")"
+    [ "$a" = "$b" ] || bad "mipmap/$n at $d ($got) is $a, not the overlay's $b"
+done; done
+echo "== icon: adaptive + monochrome, five densities, by resource table ($(basename "$(dirname "$A2")")); release re-encodes the bytes, so dimensions only"