Sony DPT-CP1 stylus annotation — v1

First release of this fork for the Sony DPT-CP1 (and likely other Sony Marvell EPDC devices). Brings KOReader's annotation workflow to feature-parity with Sony's own NoteCreator on-screen latency.

What's new vs upstream KOReader

• Kernel-fast ink under the pen. Uses Sony's Direct Handwriting (DHW) kernel path — the digitizer driver paints stylus pixels straight to /dev/graphics/fb0 with near-zero perceptual lag.
• Userspace overlay in DU mode. Stacked above KOReader's native page surface so strokes survive SurfaceFlinger composites (`NOCONVERT_DU + SP1_IGNORE` waveform).
• Coalescing render thread. Decouples touch-event rate (~100 Hz) from EPD-waveform rate (~8 Hz). No more stutter after fast multi-stroke writing.
• `pencil.koplugin` bundled. Annotate documents with the stylus: pen, eraser (tip + side button), highlight, color picker. No manual install on `/sdcard/koreader/plugins/` needed.
• Eraser button works. Side-button-held stylus events promote to eraser through both the JNI overlay path and the evdev cook path.
• Save-on-lifecycle policy. Strokes persist on page change / document close, not during writing — no disk I/O on the input thread.
• Menu position. `Pencil` is the first entry in Tools in both Reader and File Manager menus.

Install

```bash
adb install -r koreader-android-arm-v2026.03-143-gd03a090ce_2026-05-30.apk
```

If upgrading from a build signed with a different certificate, `adb uninstall org.koreader.launcher` first.

Build

```bash
git clone --recursive https://github.com/plateaukao/koreader.git
cd koreader
docker run --rm --platform linux/amd64 \
-v "$PWD:/home/ko/koreader" -w /home/ko/koreader \
--entrypoint bash koreader/koandroid:0.9.7-22.04 \
-lc './kodev release android-arm'
```

Architecture write-up

Full ADR with sequence diagrams: plateaukao.github.io/ADR/#koreader-sony-stylus-debug-and-refactor.md

Tested on

• Sony DPT-CP1 (Android 5.1, firmware 1.6.50.14130)

Other Sony Marvell EPDC devices (DPT-RP1, etc.) should work but are untested.