Tom Riddle's diary from Harry Potter and the Chamber of Secrets, running on BOOX e-ink tablets: write with the pen, the page drinks your ink, and a moment later the diary writes back in a flowing hand.
Demo video: on Xiaohongshu
A fork of billtt/boox-riddle-diary (itself inspired by MaximeRivest/riddle for the reMarkable), extended and tested on a BOOX Tab 10C (T10C, Android 12, firmware 4.2).
The Onyx SDK's hardware pen pipeline appears dead on recent firmware: the
upstream author on a Note X2 (Android 11) and this fork on a Tab 10C
(Android 12) both hit the same symptom — RawInputReader: Empty region detected when mapping!!!!! in logcat, with pen callbacks staying silent.
Upstream therefore implemented software-rendered live ink (necessarily a
little behind the pen, an e-ink refresh limitation) and documented the
symptom carefully in the dev notes — that record is what made the root-cause
diagnosis in this fork possible.
A full logcat capture on the Tab 10C pinned down the root cause: the SDK
relies on the VMRuntime.setHiddenApiExemptions reflection trick to unlock
Onyx's hidden framework classes (android.onyx.handwriting.PenConfig and
friends), and the device log shows that call being refused
(blocked, core-platform-api, reflection, denied), followed by
ClassNotFoundException for those classes and the failed region mapping.
This matches Android's hidden-API enforcement, tightened since Android 11;
community success stories on older devices (the Android 9/10 era) are also
consistent with this mechanism (not verified on old hardware by this fork).
The fix, verified before/after on the Tab 10C, is one adb command:
adb shell settings put global hidden_api_policy 1With the policy relaxed, the default TouchHelper.create() hardware pipeline
works (verified on this device: real-time ink plus normal callbacks). This
fork ships with hardware ink enabled (DiaryController.HW_PEN_RENDER), plus
a minimal diagnostic activity you can drive over adb if writing ever breaks:
adb shell am start -n com.billtt.riddle/.PenProbeActivity
adb logcat -s PenProbe RawInputReader- Hardware-rendered live ink (see above) with a seamless handoff into the absorb animation (view buffer pre-painted before raw drawing is released)
- Speculative capture: the page is photographed and the AI request fired after 0.8s of pen rest — by the time the 2s absorb animation finishes, the reply is usually already there. Writing again cancels the in-flight request.
- Write-through replies: the pen is live the moment the reply finishes revealing; touching pen to page dismisses it instantly
- Canonical Tom Riddle persona with content→reply paired few-shot examples (small vision models follow examples, not rules)
- Movie-style copperplate reply font (Tangerine) for Western text, 楷书 (Ma Shan Zheng) for Chinese; diagonal top-left→bottom-right reveal sweep
- Palm rejection for the settings gesture; whole-stroke eraser unchanged
mac-infra/: optional proxy to run replies on a Claude subscription quota instead of pay-per-use API billing (see its README)
Developed and tested only on a BOOX Tab 10C (T10C, Android 12, firmware 4.2). Other Android 11+ BOOX devices are untested — the same hidden-API fix should in principle apply (upstream hit the identical symptom on a Note X2), and reports are welcome.
Two ways to have Claude play the diary:
- Anthropic API (pay-per-use). Pick the Anthropic backend in the settings dialog and paste an API key from console.anthropic.com. Replies bill per request; every current Claude model can read the handwriting image.
- Claude Pro/Max subscription (no API billing). The app can't use a
subscription directly, but
mac-infra/boox-diary-proxy.pybridges it: a small always-on proxy on your computer keeps a persistentclaudeCLI session warm and exposes an OpenAI-compatible endpoint on your LAN, so replies count against the subscription's included quota. In the app choose the OpenAI-compatible backend, base URLhttp://<computer-ip>:7272/v1, and the shared secret you set viaDIARY_PROXY_TOKEN. Warm-turn latency is ~4-8s (plus your network's round-trip to Anthropic); as a bonus, the diary remembers earlier entries within a session. Details in mac-infra/README.md.
Any other OpenAI-compatible vision endpoint works the same way (tested:
glm-4v-plus).
Grab the debug-signed APK from Releases, or build it yourself. Either way you need a computer with adb — this is not a tap-to-install app, because the pen unlock below can only be set over adb (it needs a privileged setting no app can flip itself). With USB debugging enabled on the device:
# option A — prebuilt APK from the Releases page:
adb install -r riddle-diary.apk
# option B — build from source (JDK 17, SDK 34):
./gradlew assembleDebug
adb install -r app/build/outputs/apk/debug/app-debug.apk
# then, either way:
adb shell pm enable com.billtt.riddle # BOOX freezes newly installed apps
adb shell settings put global hidden_api_policy 1 # unlock the hardware pen pipelineOn first launch the app asks for a backend and API key (see Using Claude models above). Any OpenAI-compatible vision endpoint works — the model has to be able to read your handwriting from an image.
If writing produces no ink, the pen pipeline didn't unlock: re-check the last
command and run the PenProbeActivity diagnostic above.
Write on the blank page and the ink appears under the pen in real time. Rest the pen for about two seconds and the page drinks your handwriting, fading it away in the order you wrote it; a beat later the diary answers, its reply rising word by word from the top-left corner. The reply lingers and then sinks back into the page on its own — but the pen is live the whole time, so the moment you start writing again the reply gives way (a finger tap dismisses it too). To reach the settings dialog, long-press the page with a finger while it's blank; a palm resting mid-sentence won't trigger it. The pen's eraser end clears whole strokes.
Two experimental features live on their own branches: a procedural parchment
paper background with in-app tone/texture sliders (parchment-paper), and
blood-red accent keywords the model marks in its replies (red-accent-ink).
MIT, same as upstream. Font licenses in FONT_LICENSE_OFL.txt.
Built on billtt/boox-riddle-diary and the original idea by MaximeRivest. The fork's development — the hidden-API diagnosis, the pen pipeline, and the rest — was done with Claude Code.
本项目 fork 自 billtt/boox-riddle-diary （其创意源自 reMarkable 平台的 MaximeRivest/riddle）， 在 BOOX Tab 10C（T10C，Android 12，固件 4.2） 上开发和测试。
Onyx SDK 的硬件手写管线在新固件上看似失效：上游作者在 Note X2（Android 11）
上、本分支在 Tab 10C（Android 12）上都遇到同一现象——logcat 报
RawInputReader: Empty region detected when mapping!!!!!，笔迹回调静默。
上游因此实现了软件描墨方案（受墨水屏软件刷新机制所限，墨迹会略滞后于笔尖），
并在开发笔记中细致记录了这一症状——那份记录正是本分支得以定位根因的起点。
在 Tab 10C 上抓取完整 logcat 后定位到根因：SDK 依赖
VMRuntime.setHiddenApiExemptions 反射技巧来解锁 Onyx 固件的隐藏类
（android.onyx.handwriting.PenConfig 等），而本机日志明确显示该调用被系统
拒绝（blocked, core-platform-api, reflection, denied），随后这些隐藏类
ClassNotFoundException、区域映射失败。这与 Android 11 起收紧的
hidden API enforcement 政策相符；社区在更老设备（Android 9/10 时代）上的
成功案例也与该机制吻合（本分支未在老设备上亲测）。
在 Tab 10C 上实测有效的解法只要一条 adb 命令：
adb shell settings put global hidden_api_policy 1放行之后，默认的 TouchHelper.create() 硬件管线即可工作（本机前后对照验证：
墨迹实时渲染 + 回调正常）。本分支默认启用硬件墨迹
（DiaryController.HW_PEN_RENDER），并附带一个可用 adb 驱动的最小诊断页，
书写异常时可以快速定位：
adb shell am start -n com.billtt.riddle/.PenProbeActivity
adb logcat -s PenProbe RawInputReader- 硬件渲染的实时墨迹（见上），并做了墨迹到吸收动画的无闪交接 （关闭硬件层之前先把笔迹画入 View 缓冲）
- 投机预取：停笔 0.8 秒即截图并发起 AI 请求——等 2 秒吸收动画放完， 回信多半已经在路上；期间再落笔会自动作废在途请求
- 即回即写：回信浮现完成的瞬间笔即恢复，落笔立刻让回信让位
- 原著对齐的汤姆·里德尔人设，采用「页面内容 → 回信」配对 few-shot 示例 （小型视觉模型跟示例、不跟规则）
- 西文回信使用电影气质的铜版体（Tangerine），中文使用楷书（马善政）； 回信以左上 → 右下的对角扫掠浮现
- 设置手势加入防手掌误触；整笔橡皮擦除保持上游行为
mac-infra/：可选的 Mac 端代理，让回信走 Claude 订阅的包含额度而非按量 API 计费（详见该目录 README）
仅在 BOOX Tab 10C（T10C，Android 12，固件 4.2） 上开发和验证过。其他 Android 11+ 的 BOOX 设备未经测试——理论上同一个隐藏 API 修复应当适用 （上游作者在 Note X2 上遇到的是完全相同的症状），欢迎反馈。
让 Claude 扮演这本日记有两条路：
- Anthropic API（按量计费）。 在设置里选 Anthropic 后端，填入 console.anthropic.com 申请的 API key。按请求计费；当前所有 Claude 模型 都能读手写截图。
- Claude Pro/Max 订阅（不产生 API 账单）。 app 无法直接使用订阅，但
mac-infra/boox-diary-proxy.py可以架桥：在你的电脑上跑一个常驻小代理， 内部维持一个持久的claudeCLI 会话，对局域网暴露 OpenAI 兼容接口—— 回信消耗的是订阅的包含额度。app 里选 OpenAI 兼容后端，Base URL 填http://<电脑IP>:7272/v1，API key 填你通过DIARY_PROXY_TOKEN设置的 共享密钥。暖会话延迟约 4–8 秒（外加你到 Anthropic 的网络往返）；附带 彩蛋：同一会话内日记记得你之前写过的内容。详见 mac-infra/README.md。
其他任何 OpenAI 兼容的视觉模型接口同样可用（实测：glm-4v-plus）。
从 Releases 下载 debug 签名的 APK，或自行编译。无论哪种方式都 需要一台带 adb 的电脑——它不是点一下就能装的应用，因为下面的手写解锁只能 通过 adb 设置（那是普通 app 无权翻动的特权开关）。在设备上开启 USB 调试后：
# 方式 A —— 用 Releases 页的预编译 APK：
adb install -r riddle-diary.apk
# 方式 B —— 从源码编译（JDK 17，SDK 34）：
./gradlew assembleDebug
adb install -r app/build/outputs/apk/debug/app-debug.apk
# 然后，两种方式都要：
adb shell pm enable com.billtt.riddle # BOOX 会冻结新装应用
adb shell settings put global hidden_api_policy 1 # 解锁硬件手写管线首次启动时 app 会询问后端与 API Key（见上文《连接 Claude 模型》）。任何 OpenAI 兼容的视觉接口都可以——模型必须能从截图里读出你的手写。
若书写没有墨迹，说明手写管线未解锁：复查最后一条命令，并运行上文的
PenProbeActivity 诊断页。
在空白页上落笔，墨迹实时出现在笔尖下。停笔约两秒，纸面把你的字迹「喝」下去， 按你书写的顺序淡去；片刻之后日记开始回信，回信从左上角逐字浮起。回信停留片刻 后会自行沉回纸中——但笔全程是活的，你一旦重新落笔，回信立即让位（手指点一下 也能让它消散）。想打开设置，在空白页上用手指长按即可；写到一半搁下的手掌不会 误触。笔的橡皮端可整笔擦除。
两个实验性功能各在独立分支：带应用内色深/纹理滑杆的程序化羊皮纸背景
（parchment-paper），以及模型在回信中标注的血红关键词（red-accent-ink）。
MIT，与上游一致。字体许可见 FONT_LICENSE_OFL.txt。
基于 billtt/boox-riddle-diary 及 MaximeRivest 的原始创意。本分支的 开发——隐藏 API 的诊断、手写管线、以及其余部分——借助 Claude Code 完成。