PillarBox

Per-app 4:3 aspect engine for wide Android tablets.

Pick the games that were designed around an iPad Pro viewport, and PillarBox makes those apps run inside a real 4:3 viewport on a 16:10 or 3:2 tablet — then puts everything back the moment you leave the app.

Pixel count unchanged. Viewport ratio changed. FOV math matches the iPad build.

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Why

The iPad Pro is 4:3. Games are tuned against it: vertical FOV, HUD anchors, minimap position, menu column widths. A 16:10 or 3:2 Android tablet gives the renderer a wider viewport, so the same game either stretches the horizontal FOV, pulls the camera back, or reflows the HUD into a shape it was never designed for.

PillarBox gives selected apps the geometry they expect, without touching the panel.

What it actually does

PillarBox is not a hook and it does not patch game memory. It changes the logical display geometry of the device while a selected app is in front:

1. A root daemon watches the top resumed activity once per second.
2. When the package is in config.json, it computes the largest 4:3 rectangle that fits your panel, aligned to 8 px, plus a proportionally scaled density.
3. It applies wm size <w>x<h> and wm density <dpi>.
4. Launcher, system UI, screen off, or any app not in the list → wm size reset and wm density reset.

Because the override is the real display configuration, every consumer of DisplayMetrics and Configuration sees 4:3 — the renderer, the layout engine, and the game's own aspect detection. That is the difference between a real 4:3 viewport and a spoof that only lies to one API and produces a distorted image.

What you get, and what you don't

Real 4:3 render target	Yes — the app renders 4:3 natively
iPad-style FOV and HUD anchoring	Yes
Extra screen real estate	No — 4:3 inside a wider panel means pillarbox bars
Panel change	None
Per-app granularity	Yes, list-based
System-wide side effects	Only while a selected app is foreground; the display geometry is restored on exit

Expect a short resize animation when the engine switches, and a briefly resized system UI if you pull down the shade while a game is framed. That is the cost of a real viewport change instead of a fake one.

Games that cache display metrics at launch should be restarted once after being added.

Install

Requirements: rooted tablet (Magisk or KernelSU), Android 11+.

1. Flash PillarBox-Module-v1.0.0.zip in Magisk / KernelSU, reboot.
2. Install PillarBox-1.0.0.apk.
3. Open it, grant superuser.
4. Add apps, pick the games, choose a ratio (4:3 by default), done.

The APK also works without the module: it deploys the same engine to /data/local/tmp/pillarbox and runs it from there. The module only makes it survive reboots from /data/adb/pillarbox.

Ratios

4:3 is the one you want for iPad parity. The list also carries 16:10, 16:9, 5:4, 3:2 and 1:1 for experiments — clipping a game to a narrower viewport is sometimes useful for competitive framing.

Config

The app writes this; you can also edit it by hand.

{
  "enabled": true,
  "apps": {
    "com.mojang.minecraftpe": "4:3",
    "com.tencent.ig": "4:3",
    "com.miHoYo.GenshinImpact": "16:10"
  }
}

Path: /data/adb/pillarbox/config.json (module) or /data/local/tmp/pillarbox/config.json (standalone).

Engine CLI

su -c "/data/adb/pillarbox/pillarboxd start"
su -c "/data/adb/pillarbox/pillarboxd status"
su -c "/data/adb/pillarbox/pillarboxd stop"

stop also restores the display. Logs land in engine.log next to the config, capped at 128 KB.

Build

Windows, JDK 21, Android SDK with platform 34, Gradle 8.11.1.

.\build.ps1

build.ps1 normalises line endings, stages the daemon into the APK assets, runs :app:assembleRelease, and packages dist/PillarBox-1.0.0.apk plus dist/PillarBox-Module-v1.0.0.zip.

Manual equivalent:

$env:JAVA_HOME="C:\path\to\jdk-21"
gradle -p . :app:assembleRelease --no-daemon

The release keystore lives in signing/pillarbox.jks with the password pillarbox. It is published on purpose: forks should be able to produce an APK with the same signature so updates install over the official build.

Layout

app/                     Compose + Material 3 companion app
  data/                  root bridge, config model, engine control, app inventory
  ui/                    home screen, ratio sheet, app picker, theme
module/                  Magisk / KernelSU package
  bin/pillarboxd         the engine (POSIX sh, no dependencies)
  service.sh             boot start
  customize.sh           installs the engine into /data/adb/pillarbox
  uninstall.sh           stops the engine and restores the display

Notes and limits

• Root is required. wm needs shell/root and the daemon needs to survive the app being swiped away.
• Some ROMs animate or re-layout more aggressively on display change; HyperOS and One UI both behave, AOSP is the cleanest.
• Anti-cheat: this is a developer-options display-size change, not memory injection, not a hook. It is still a non-standard display configuration — decide for yourself how your game's anti-cheat feels about that.
• Not tested on foldables. The daemon reads the physical size at runtime, so it should follow the panel, but folding mid-session is untested.

License

MIT. Fork it, ship it, break it.