reMarkable 2 support: AppLoad windowed mode and xochitl companion mode

.gitignore

@@ -9,3 +9,5 @@ oracle.env
 riddle/dist/
 drawlab/dist/
 home/dist/
+riddle/riddle-rm2
+.DS_Store

README-RM2.md

@@ -0,0 +1,49 @@
+# riddle for reMarkable 2 — no XOVI or AppLoad
+
+This build runs beside the stock reMarkable UI on RM2 firmware 3.28. It reads
+real Wacom strokes without grabbing the device, sends a private reconstruction
+of the writing to the configured vision model, and replays the reply through
+the Wacom input device. xochitl records Tom's handwriting in the open notebook
+as ordinary ink.
+
+## Install
+
+Copy the extracted `riddle-rm2` directory to `/home/root/riddle-rm2`, then:
+
+```sh
+cd /home/root/riddle-rm2
+cp oracle.env.example oracle.env
+vi oracle.env                 # set RIDDLE_OPENAI_KEY
+chmod +x riddle-rm2 start-rm2.sh stop-rm2.sh
+```
+
+No root filesystem files, startup hooks, XOVI, AppLoad, or systemd units are
+installed.
+
+## Use
+
+Open a blank notebook in the stock UI and write in its upper third. From SSH:
+
+```sh
+/home/root/riddle-rm2/start-rm2.sh
+```
+
+After a 2.8 second pause, Tom writes back through xochitl. Stop it before using
+other parts of the UI:
+
+```sh
+/home/root/riddle-rm2/stop-rm2.sh
+```
+
+This companion build intentionally does not erase/fade existing notebook ink
+and disables the takeover-only help and memory-page animations. The original
+notebook remains a normal reMarkable document and syncs normally.
+
+## Remove
+
+```sh
+/home/root/riddle-rm2/stop-rm2.sh
+rm -rf /home/root/riddle-rm2 /home/root/riddle-data
+```
+
+Rebooting also stops it because no autostart component is installed.

riddle/Cargo.toml

@@ -3,7 +3,7 @@ name = "riddle"
 version = "0.3.0"
 edition = "2021"
 license = "MIT"
-description = "The diary of Tom Riddle, for the reMarkable Paper Pro"
+description = "The diary of Tom Riddle, ported to the reMarkable 2"
 
 [dependencies]
 libc = "0.2"

riddle/appload-rm2.sh

@@ -0,0 +1,9 @@
+#!/bin/sh
+set -eu
+cd "$(dirname "$0")"
+if [ -f oracle.env ]; then
+    set -a
+    . ./oracle.env
+    set +a
+fi
+exec ./riddle-rm2

riddle/build-rm2.sh

@@ -0,0 +1,16 @@
+#!/bin/sh
+# Build the windowed reMarkable 2 AppLoad binary.
+set -eu
+cd "$(dirname "$0")"
+
+TARGET=armv7-unknown-linux-gnueabihf
+if command -v cross >/dev/null 2>&1; then
+    cross build --release --target "$TARGET"
+else
+    : "${CARGO_TARGET_ARMV7_UNKNOWN_LINUX_GNUEABIHF_LINKER:=arm-linux-gnueabihf-gcc}"
+    export CARGO_TARGET_ARMV7_UNKNOWN_LINUX_GNUEABIHF_LINKER
+    cargo build --release --target "$TARGET"
+fi
+
+cp "target/$TARGET/release/riddle" riddle-rm2
+echo "built: $(pwd)/riddle-rm2"

riddle/external.manifest.json

@@ -1,8 +1,9 @@
 {
   "id": "riddle",
   "name": "The Diary",
-  "version": "0.3.0",
+  "version": "0.3.0-rm2.2",
   "description": "An enchanted diary: write to it with the pen — it writes back, and it remembers.",
-  "application": "appload-launch.sh",
-  "qtfb": false
+  "application": "appload-rm2.sh",
+  "qtfb": true,
+  "aspectRatio": "original"
 }

riddle/src/display.rs

@@ -7,6 +7,9 @@ use std::io;
 
 pub enum Display {
     Qtfb(crate::qtfb::QtfbClient),
+    /// Headless companion mode: xochitl owns the real panel while riddle
+    /// renders into this private RGB565 page for OCR and layout.
+    Xochitl(Box<[u8]>),
     #[allow(dead_code)]
     Quill,
 }
@@ -31,18 +34,36 @@ impl Display {
             let key: i32 = key.parse().map_err(io::Error::other)?;
             let mut client = crate::qtfb::QtfbClient::connect(
                 key,
-                crate::qtfb::FBFMT_RMPP_RGB565,
-                1620,
-                2160,
+                crate::qtfb::FBFMT_RM2FB,
+                crate::fb::SCREEN_W,
+                crate::fb::SCREEN_H,
                 2,
             )?;
             let _ = client.set_refresh_mode(crate::qtfb::REFRESH_MODE_UFAST);
             let buf = client.framebuffer();
             let (ptr, len) = (buf.as_mut_ptr(), buf.len());
-            let surface = Surface::new(ptr, len, 1620, 2160, 1620 * 2, PixFmt::Rgb565);
+            let surface = Surface::new(
+                ptr, len, crate::fb::SCREEN_W, crate::fb::SCREEN_H,
+                crate::fb::SCREEN_W * 2, PixFmt::Rgb565,
+            );
             return Ok((Display::Qtfb(client), surface));
         }
 
+        // reMarkable 2 needs no launcher: keep the stock UI running and use
+        // its Wacom input path to replay Tom's generated handwriting.
+        #[cfg(not(feature = "takeover"))]
+        {
+            let mut page = vec![0xff; crate::fb::SCREEN_W * crate::fb::SCREEN_H * 2]
+                .into_boxed_slice();
+            let ptr = page.as_mut_ptr();
+            let len = page.len();
+            let surface = Surface::new(
+                ptr, len, crate::fb::SCREEN_W, crate::fb::SCREEN_H,
+                crate::fb::SCREEN_W * 2, PixFmt::Rgb565,
+            );
+            return Ok((Display::Xochitl(page), surface));
+        }
+
         #[cfg(feature = "takeover")]
         {
             unsafe {
@@ -60,10 +81,6 @@ impl Display {
                 Ok((Display::Quill, surface))
             }
         }
-        #[cfg(not(feature = "takeover"))]
-        Err(io::Error::other(
-            "QTFB_KEY not set and this build has no takeover backend",
-        ))
     }
 
     /// Push a region to the panel. `fast` selects the low-latency waveform.
@@ -72,6 +89,7 @@ impl Display {
             Display::Qtfb(c) => {
                 let _ = c.update_partial(x, y, w, h);
             }
+            Display::Xochitl(_) => {}
             #[allow(unused_variables)]
             Display::Quill => {
                 #[cfg(feature = "takeover")]
@@ -89,6 +107,7 @@ impl Display {
             Display::Qtfb(c) => {
                 let _ = c.update_all();
             }
+            Display::Xochitl(_) => {}
             #[allow(unused_variables)]
             Display::Quill => {
                 #[cfg(feature = "takeover")]
@@ -107,6 +126,7 @@ impl Display {
             Display::Qtfb(c) => {
                 let _ = c.request_full_refresh();
             }
+            Display::Xochitl(_) => {}
             #[allow(unused_variables)]
             Display::Quill => {
                 #[cfg(feature = "takeover")]
@@ -124,6 +144,7 @@ impl Display {
     pub fn pump(&self) -> io::Result<Vec<crate::qtfb::InputEvent>> {
         match self {
             Display::Qtfb(c) => c.drain_events(),
+            Display::Xochitl(_) => Ok(Vec::new()),
             Display::Quill => {
                 #[cfg(feature = "takeover")]
                 unsafe {

riddle/src/fb.rs

@@ -1,7 +1,8 @@
 //! Geometry helpers. Drawing lives in surface.rs.
 
-pub const SCREEN_W: usize = 1620;
-pub const SCREEN_H: usize = 2160;
+// reMarkable 1/2 native portrait framebuffer.
+pub const SCREEN_W: usize = 1404;
+pub const SCREEN_H: usize = 1872;
 
 /// Grow-only pixel bounding box, used to build update/dissolve regions.
 #[derive(Clone, Copy, Debug)]