StuffMIDIMessage feeds the virtual MIDI keyboard, which only reaches tracks that are armed and monitoring -- normally not the track whose item you are editing. Opening an item in grid mode therefore sounded every preview through whatever instrument happened to be armed, which is confusing when the notes you are writing come back in the wrong voice. Grid mode now borrows the record routing: the edited take's track is armed and monitoring with all MIDI inputs (anything narrower can exclude the virtual keyboard), and every other armed track is stood down so it cannot answer as well. The prior arm, monitor and input of each track touched is saved by GUID in transient ExtState. routePreview re-points lazily, so moving the editor to an item on another track costs nothing until the target actually changes. The daemon hands the routing back when grid mode goes off, when the editor closes, or on exit -- the same way it already restores the loop and repeat state the loop-bar action borrows -- so the project is put back even if grid mode is never toggled off. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
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CLAUDE.md
This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
What this is
A REAPER MIDI-editor grid/step-entry mode written in Lua, built for
keyboard-and-speech use with OSARA. Pure ReaScript — no ReaPack, no
js_ReaScriptAPI, no ReaImGui. README.md is the user manual and is unusually
detailed; read the relevant section before changing behaviour, and update it
when behaviour changes.
Commands
lua test_lib.lua # run the tests
powershell -ExecutionPolicy Bypass -File install.ps1 # install on Windows (REAPER must be CLOSED)
powershell -ExecutionPolicy Bypass -File install.ps1 -Uninstall
./install.sh # install on macOS/Linux
./install.sh --uninstall
There is no build, no lint, no package manager, no test framework. test_lib.lua
is a single script of eq(got, want, label) assertions printing ALL PASS or a
failure count; to run one case, comment out the others. It stubs a global
reaper table, so it only covers the pure logic (scale stepping, note naming,
grid labels, chord construction). Anything touching MIDI data or the REAPER API
can only be exercised inside REAPER. Note it dofiles an absolute path to
midigrid_lib.lua.
Architecture
midigrid_lib.lua holds essentially all the logic as module M. Every
action script is a thin adapter: resolve its own directory from
reaper.get_action_context(), dofile the lib, check G.isActive(), and either
G.passThrough(...) or call a couple of lib functions. New behaviour belongs in
the lib; new action scripts should stay ~10 lines.
No private cursor state. Time is REAPER's edit cursor; pitch is the MIDI
editor's active_note_row; cell size is MIDI_GetGrid(). This is what lets grid
mode and plain OSARA editing interleave without drifting, and why the user's
existing grid-size keybindings just work. Do not introduce a cursor of your own.
Action scripts must never call reaper.defer. A still-running script makes
REAPER show its "already running — terminate or launch new instance?" prompt on
the next keypress, which destroys key repeat. All timing lives in
MidiGrid_Daemon.lua, one background loop that auto-starts (G.ensureDaemon()),
heartbeats via ExtState, refuses to start a second copy, and releases notes on
atexit. Actions post a request to ExtState and exit immediately. If you need
something to happen later — note release, stop-at-bar-end, restoring borrowed
loop/repeat state — add it to the daemon loop, not to an action.
ExtState section midigrid is the only state. Persisted (M.set/M.get):
active, hold, root, scale, vel, velstep, chan, previewdur,
stoplead. Transient (M.setTemp/M.getTemp, persist flag false): seq,
pitches, dur, hb, stopat, stoparm, savedloop, savedrep,
savedarm, routed. Preview traffic must stay transient — persisting it
would write reaper.ini on every keypress.
Preview is routed to the edited track. StuffMIDIMessage feeds the virtual
MIDI keyboard, which only reaches armed, monitoring tracks, so M.routePreview
borrows the record arm/monitor/input of the take's track (standing down other
armed tracks) and M.restoreRouting hands it all back. M.preview re-points
lazily on every call, so switching items just works. The daemon restores when
grid mode goes off, the editor closes, or REAPER exits.
Every grid key falls back. When grid mode is off, each bound key forwards to
what it did before via G.passThrough (e.g. _OSARA_PREVCHORD, or a numeric
command id), so nothing is permanently taken away.
All feedback is speech, via G.say → osara_outputMessage, falling back to
the console when OSARA is absent. There is no window and no gfx.
Musical positions are converted through quarter-notes (MIDI_GetPPQPosFromProjQN
and friends), not raw ticks, so edits stay correct across tempo changes.
Installation model
install.ps1 (Windows) and install.sh (macOS/Linux) edit reaper-kb.ini
directly and are idempotent (they strip all RSmidigrid lines first, and back
up to reaper-kb.ini.midigrid-backup). REAPER rewrites that file on exit, so
it must be closed or changes are lost. The two scripts are deliberate mirrors:
same action list, same key table, same output. Any change to one must be made
to the other. They differ only in resource-path discovery
(%APPDATA%\REAPER vs ~/Library/Application Support/REAPER) and in
install.sh --real-control, which exists because modifier bit 8 means Ctrl on
Windows but Command on macOS (physical Control is bit 32).
Adding a new action means adding a row to both tables in each installer: the
$actions table (SCR 4 <section> <id> "<description>" <path>) and, if it needs
a key, $keys (flags: 1 base, +4 Shift, +8 Ctrl, +16 Alt; section 0 = Main,
32060 = MIDI Editor). KEY lines must reference the named command — the SCR id
with a leading underscore (_RSmidigrid_open). Without the underscore REAPER
silently converts the binding to a no-op; this is exactly why importing
MidiGrid.ReaperKeyMap does not work and the file is kept for reference only.