Stratum

Native Android overlay framework. Fullscreen OpenGL ES 2.0 surface, raw input, ~60fps render loop. No Activity, no framework, no JVM.

Talks directly to SurfaceFlinger via SurfaceComposerClient, creates a surface at INT_MAX layer, reads raw input events from /dev/input/ in a dedicated thread.

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Device Support

Stratum is device-specific by design. Each supported device lives under devices/:

devices/
└── <model>/
    ├── StratumConfig.h   ← device paths and touch parameters
    ├── app.cpp           ← your application entry point
    ├── stratum-boot/     ← KernelSU module source
    └── out/              ← build output (gitignored)

To add a new device, fork the repo and create devices/<model>/ with StratumConfig.h and app.cpp. Use src/default.cpp as a starting point for app.cpp.

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Building

bash scripts/build.sh <device>          # build everything
bash scripts/build.sh <device> -l       # lib only (no examples)
bash scripts/build.sh <device> -e       # examples only
bash scripts/build.sh <device> piano    # specific example(s)

Output goes to devices/<device>/out/. A flashable KernelSU module zip is produced at devices/<device>/out/<device>-stratum-boot.zip.

Requires Clang targeting aarch64-linux-android34 and AOSP private headers included under include/.

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Running

bash scripts/run.sh <device>                  # run your app
bash scripts/run_example.sh <device> <app>    # run a specific example

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API

Stratum s;
s.init();
s.onFrame([](float t) { /* t = seconds since run() */ });
s.onKey([](const KeyEvent& e) { /* e.code, e.action, e.time */ });
s.onTouch([](const TouchEvent& e) { /* e.x, e.y, normalised 0..1 */ });
s.run();   // blocks until stop()
s.stop();  // safe to call from any callback

s.width();    // px
s.height();   // px
s.aspect();   // width / height

Stratum::vibrate(ms);
Stratum::setBrightness(0..255);
Stratum::log(tag, fmt, ...);

KeyEvent

Field	Type	Notes
code	int	Linux keycode (KEY_POWER, KEY_VOLUMEUP, ...)
action	KeyAction	DOWN, UP, REPEAT
time	float	CLOCK_MONOTONIC seconds

Software repeat fires after 0.5s, then every ~33ms.

TouchEvent

Field	Type	Notes
slot	int	Multitouch slot
id	int	Tracking ID
action	TouchAction	DOWN, MOVE, UP
x, y	float	Normalised 0.0..1.0
time	float	CLOCK_MONOTONIC seconds

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Configuration

devices/<model>/StratumConfig.h — device-specific paths and touch parameters:

namespace StratumConfig {
    const char* TOUCH_DEVICE   = "/dev/input/eventX";
    const char* KEY_DEVICE     = "/dev/input/eventY";
    const char* KEY_DEVICE2    = "";        // optional
    int  TOUCH_PROTOCOL        = 0;         // 0 = auto, 1 = proto A, 2 = proto B
    int  TOUCH_SLOTS           = 10;
    int  TOUCH_X_MIN = 0, TOUCH_X_MAX = 0; // 0 = read from device at runtime
    int  TOUCH_Y_MIN = 0, TOUCH_Y_MAX = 0;
    const char* VIBRATOR       = "/sys/class/timed_output/vibrator/enable";
    const char* BRIGHTNESS     = "/sys/class/leds/lcd-backlight/brightness";
    int  BRIGHTNESS_MIN = 0, BRIGHTNESS_MAX = 255;
}

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Helpers

StratumText.h — 8x8 bitmap font, GL texture atlas, no external files.

Text::init(s.aspect(), prog);
Text::draw(str, x, y, size, r, g, b);
Text::drawWrapped(str, x, y, size, maxW, r, g, b);
float cw = Text::charW(size, aspect);

StratumArgs.h — timeout argument parser for examples.

float t = parseTimeout(argc, argv);
// accepts: N, -t N, -t=N, --timeout=N, --help
// default: 0 (unlimited)

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Examples

Examples are maintained in a separate repository and linked here as a submodule at apps/:

git submodule update --init

See stratum-apps for the full list.

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KernelSU Module

devices/<model>/stratum-boot/ is a per-device KernelSU module. It installs the runtime to /system/bin and /system/lib64 and launches stratum_binary early via post-fs-data.sh, before the Android framework starts.

The flashable zip is built automatically and output to devices/<model>/out/<model>-stratum-boot.zip.

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Requirements

• Root (KernelSU or Magisk)
• Clang targeting aarch64-linux-android34

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License

Copyright (C) 2026 BrotherBoard — GNU General Public License v3.0. See LICENSE.