CMP onPostScroll Desktop Bug Repro

Small Kotlin Multiplatform + Compose Multiplatform project that demonstrates a nested scroll issue on Desktop JVM.

Project Shape

• shared: KMP library module with shared Compose UI.
• androidApp: Android application launcher that calls App() from shared.
• desktopApp: Desktop JVM application launcher that calls App() from shared.

Repro

Run Desktop:

./gradlew :desktopApp:run

Run Android:

./gradlew :androidApp:installDebug

Scroll to the top or bottom edge and keep scrolling past the edge. The centered surface displays:

• onPostScroll available.y
• callback call count
• nested scroll source
• current scroll offset

Expected behavior: onPostScroll keeps receiving the unconsumed delta at the scroll edge. Android does this. On Desktop JVM, the callback is not invoked for wheel scroll at the beginning/end, which is the bug this sample isolates.

This sample's onPostScroll handler consumes the incoming available offset by returning it. That means the parent nested-scroll handler takes precedence over overscroll. Desktop overscroll being disabled is acceptable for this repro; the expected behavior is still that onPostScroll is invoked with the unconsumed edge delta before any overscroll handling would matter.

Verification

./gradlew :shared:jvmTest
./gradlew :desktopApp:jar :androidApp:assembleDebug