Initial commit: Chatter — assistive-writing app for reMarkable Paper Pro Move

Direct-framebuffer ink pipeline (stock-quality strokes), finger-wipe erase,
growable scrolling canvas with color-ghost cleanup, bidirectional toggle with a
persistent 4-finger return launcher, instant button feedback. Includes prebuilt
aarch64 binaries (dist/), build/deploy/install scripts, a user guide, and a
complete technical reference.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tools/swapshim.cpp

@@ -0,0 +1,46 @@
+// LD_PRELOAD trace shim: intercept EPFramebuffer::swapBuffers in libqsgepaper to
+// learn the exact (contentType, screenMode, flags) the stock app uses for pen
+// strokes. We define functions with the real mangled names so the dynamic loader
+// interposes them, log the args, then chain to the real implementation.
+//
+// QRect is passed by value; its memory layout is {int x1,y1,x2,y2} (l,t,r,b), so
+// we model it as a 16-byte POD to match the ABI without linking Qt. The enums and
+// QFlags are all 4-byte int-sized.
+
+#include <dlfcn.h>
+#include <cstdio>
+
+struct RawRect { int x1, y1, x2, y2; };
+
+extern "C" {
+
+// swapBuffers(QRect, EPContentType, EPScreenMode, QFlags<UpdateFlag>)
+void _ZN13EPFramebuffer11swapBuffersE5QRect13EPContentType12EPScreenMode6QFlagsINS_10UpdateFlagEE(
+    void *self, RawRect r, int contentType, int screenMode, int flags)
+{
+    static void (*real)(void *, RawRect, int, int, int) = nullptr;
+    if (!real)
+        real = (void (*)(void *, RawRect, int, int, int))dlsym(
+            RTLD_NEXT,
+            "_ZN13EPFramebuffer11swapBuffersE5QRect13EPContentType12EPScreenMode6QFlagsINS_10UpdateFlagEE");
+    fprintf(stderr, "SWAPTRACE1 rect=(%d,%d)-(%d,%d) %dx%d content=%d screen=%d flags=%d\n",
+            r.x1, r.y1, r.x2, r.y2, r.x2 - r.x1 + 1, r.y2 - r.y1 + 1,
+            contentType, screenMode, flags);
+    if (real) real(self, r, contentType, screenMode, flags);
+}
+
+// swapBuffers(const QRegion&, const EPContentMap&, const EPScreenModeMap&, QFlags<UpdateFlag>)
+void _ZN13EPFramebuffer11swapBuffersERK7QRegionRK12EPContentMapRK15EPScreenModeMap6QFlagsINS_10UpdateFlagEE(
+    void *self, const void *region, const void *contentMap, const void *modeMap, int flags)
+{
+    static void (*real)(void *, const void *, const void *, const void *, int) = nullptr;
+    if (!real)
+        real = (void (*)(void *, const void *, const void *, const void *, int))dlsym(
+            RTLD_NEXT,
+            "_ZN13EPFramebuffer11swapBuffersERK7QRegionRK12EPContentMapRK15EPScreenModeMap6QFlagsINS_10UpdateFlagEE");
+    fprintf(stderr, "SWAPTRACE2 region=%p contentMap=%p modeMap=%p flags=%d\n",
+            region, contentMap, modeMap, flags);
+    if (real) real(self, region, contentMap, modeMap, flags);
+}
+
+} // extern "C"