ImMidiMapper

Map any Dear ImGui control to a MIDI CC — right-click to learn, zero extra dependencies.

Pure C++17 + Dear ImGui extension. No platform SDK in the core.
MIDI I/O is a plug-in callback interface — bring your own backend, or use the included RtMidi backend.

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Features

• Two registration patterns — wrapper widgets or watchLast() after any existing ImGui:: call
• Right-click MIDI Learn on any registered control
• Indicator dot — gray (unbound) · green (mapped) · pulsing yellow (learning)
• Two-way sync — drag a UI control → send CC back to hardware
• Persistence — save/load mappings as JSON (hand-rolled, no extra dependency)
• Editor window — full binding table, inline CC editing, port selector
• Cross-platform — macOS · Windows · Linux (CMake + FetchContent, no manual installs)

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Quick start

// One translation unit only:
#define IMMIDIMAPPER_IMPLEMENTATION
#include "ImMidiMapper.h"
#include "ImMidiMapperRtMidi.h"   // optional — RtMidi backend

ImMidiMapperRtMidi mapper;
mapper.openInputPort(0);           // first available port

// main loop:
mapper.update();                   // flush MIDI queue → bound variables

// inside ImGui block — two patterns:

// 1. Wrapper widgets (drop-in ImGui:: replacements)
mapper.SliderFloat("cutoff",    "Cutoff",    &params.cutoff,    0.f, 1.f);
mapper.SliderFloat("resonance", "Resonance", &params.resonance, 0.f, 1.f);
mapper.Checkbox   ("square",    "Square",    &params.square);

// 2. watchLast() — after any existing ImGui:: widget
ImGui::SliderFloat("Decay", &params.decay, 0.f, 1.f);
mapper.watchLast("decay", &params.decay, 0.f, 1.f);

// Works with custom widgets too (knobs, dials, etc.):
MyKnob("Env Mod", &params.envMod, 40.f);
mapper.watchLast("env_mod", &params.envMod, 0.f, 1.f);

// Editor with built-in port selector:
mapper.drawEditor(&editorVisible);

// Persist:
mapper.save("midiMapper.json");
mapper.load("midiMapper.json");

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Building

git clone https://github.com/you/ImMidiMapper.git
cd ImMidiMapper
cmake -B build
cmake --build build
./bin/ImMidiMapperDemo

All dependencies (Dear ImGui, SDL2, RtMidi) are fetched automatically by CMake.

Platform notes

Platform	MIDI backend	Extra requirement
macOS	CoreMIDI (built-in)	Xcode CLT: xcode-select --install
Windows	WinMM (built-in)	Visual Studio 2019+ or MinGW
Linux	ALSA	sudo apt install libasound2-dev

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Architecture

ImMidiMapper.h          ← core: pure C++17 + ImGui
                          pushCC()  /  onSendCC callback
                          
ImMidiMapperRtMidi.h    ← RtMidi adapter (header-only subclass)
                          routes RtMidi → pushCC
                          sets  onSendCC → RtMidi sendMessage
                          injects port selector into drawEditor()

example/main.cpp        ← SDL2 + OpenGL3 demo

Bring your own backend

If you already have MIDI working (e.g. via ofxMidi, PortMidi, Web MIDI API):

// Core mapper — no RtMidi needed
#define IMMIDIMAPPER_IMPLEMENTATION
#include "ImMidiMapper.h"

ImMidiMapper mapper;

// Feed incoming CC from your callback (thread-safe):
void yourMidiCallback(int channel, int cc, int value) {
    mapper.pushCC(channel, cc, value);
}

// Receive CC output for two-way sync:
mapper.onSendCC = [](int ch, int cc, int val) {
    yourMidiOut.sendCC(ch, cc, val);
};

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API reference

Method	Description
pushCC(ch, cc, val)	Thread-safe CC input
pushNoteOn(ch, note, vel)	Note-on as boolean trigger
update()	Apply queued events (call every frame)
SliderFloat(id, label, &val, min, max)	Wrapper for ImGui::SliderFloat
SliderInt(id, label, &val, min, max)	Wrapper for ImGui::SliderInt
DragFloat(id, label, &val, ...)	Wrapper for ImGui::DragFloat
Checkbox(id, label, &val)	Wrapper for ImGui::Checkbox
Button(id, label, &toggle)	Wrapper for ImGui::Button
watchLast(id, &val, min, max)	Post-widget hook for any ImGui item
startLearn(id) / stopLearn()	Programmatic learn control
assign(id, channel, cc)	Manual CC assignment
clearBinding(id)	Remove a CC assignment
save(path) / load(path)	JSON persistence
drawEditor(&visible)	Full mapping editor window
bind(id, &val, ...)	Register without drawing a widget

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License

MIT