Android: what makes an app feel native
How a Zinc app is exported, built and installed is in docs/reports/zinc-next-android.md (zinc export --target android, Gradle, the
Nexus 7 runs). This page is what the app does to behave like an Android app, and how to try it on the desktop. The audit and plan behind it:
docs/reports/mobile-native-feel.md.
Try it on the desktop
ZINC_PLATFORM=android zinc run . runs the program as on Android: platform() and Platform.OS answer android, Platform.select takes the
android branch, x.android.ts replaces x.ts, and the behaviour below is Android’s. ZINC_PLATFORM_VERSION=29 plays an Android 10
(the scroll glow instead of the stretch). The OS’s signals are sent from a ZINC_INPUT script (docs/ui.md, “Platform and system signals”):
10 safearea 24 0 48 0
10 theme dark
10 fontscale 1.3
20 keyboard 280
40 back
50 backstart left
52 backprogress 0.5
54 backWhat the app does
| Area | On Android |
|---|---|
| Identity | platform() android; Platform.Version the API level (ro.build.version.sdk) |
| Safe area, theme | from SDL (SDL_GetWindowSafeArea, SDL_GetSystemTheme) at start and when they change |
| Font size, animations off | Configuration.fontScale and the animator duration scale 0, sent by the activity (ZincActivity) at start, on a configuration change and on resume |
| Keyboard | its height from the IME insets (API 30+) or the visible frame (before), so the focused field is revealed above it; the field’s traits choose the keyboard (ZincEdit.onCreateInputConnection: input type, return key action, autofill hint) |
| Text input connection | ZincEdit, in place of SDL’s hidden editor: an InputConnection over a mirror of the focused field (text, selection, composing region), so suggestions, autocorrect and composition see the real text |
| Back | the back key (SDL, trapped) and Android 13+‘s back callback go to the program’s back handlers (BackHandler, ui.addBackHandler, the navigation stack); none takes it: the task goes to the background (Android 12+‘s behaviour for a root activity). Android 14’s predictive back gesture sends its progress, and the navigation stack shrinks the screen with it |
| Scrolling | OverScroller’s spline fling, the stretch overscroll (12+) or the glow (before), no rubber band, the scrollbars’ 300 ms + 250 ms fade |
| Navigation | zinc:ui/navigation: Material’s shared X axis, the back arrow and a left-aligned title; modal screens as full-screen dialogs |
| Touch selection | a long press selects a word: teardrop handles, a white edit menu, a magnifier while a handle moves, the long-press haptic |
| Status bar | StatusBar barStyle (light or dark icons), hidden, backgroundColor (before Android 15, which draws apps edge to edge) |
| Haptics | zinc:haptics and Vibration: View.performHapticFeedback (CONFIRM, REJECT, SEGMENT_TICK where the API has them); vibrate needs the VIBRATE permission, without it a haptic tick |
The Java side is src/app/android/java (copied into the exported project), the JNI side src/app/android_glue.cpp.
Not proven on a device
Written and compiled on the Mac (javac against android-36, clang with NDK r29) without a device in the loop (2026-10-16): the keyboard height,
the input connection with Gboard, swipe typing and a Japanese IME, predictive back, the status bar, haptics and the font scale on a phone are
lines of the cross-platform pass in backlog/later.md.