Mu API Compatibility Layer

The src/compat/ module provides a compatibility bridge between desktop OpenRV's Mu scripting API and the openrv-web JavaScript runtime. It lets existing Mu-based scripts and integrations work in the browser with minimal changes.

The layer exposes window.rv.commands and window.rv.extra_commands, mirroring the namespaces that Mu scripts use in desktop OpenRV.

---

Quick Start

import { registerMuCompat } from './compat';

// Call after window.openrv (OpenRVAPI) is initialized.
// Safe to call multiple times; subsequent calls are no-ops.
const { commands, extra_commands } = registerMuCompat();

// Now use the Mu-style API:
commands.play();
commands.setFrame(100);
extra_commands.togglePlay();

// Or access globally:
window.rv.commands.play();
window.rv.extra_commands.stepForward(5);

Prerequisite

window.openrv (the core OpenRVAPI) must be initialized before calling any command. The compat layer lazily resolves it on each call, so registration order does not matter as long as the API exists before the first command runs.

---

API Reference

window.rv.commands (MuCommands)

Introspection

Method	Signature	Description
isSupported	(name: string) => true | false | 'partial'	Check if a command is supported
isAsync	(name: string) => boolean	Check if a command returns a Promise

Playback & Transport

Command	Signature	Status	Description
play	() => void	DIRECT	Start playback
stop	() => void	DIRECT	Pause playback
isPlaying	() => boolean	DIRECT	Check if playing
setFrame	(frame: number) => void	DIRECT	Seek to a specific frame
frame	() => number	DIRECT	Get current frame number
frameStart	() => number	ADD	Get frame range start (local state)
frameEnd	() => number	DIRECT	Get total frames
setFPS	(fps: number) => void	ADD	Set FPS override (local state)
fps	() => number	PARTIAL	Get effective FPS (override or media)
realFPS	() => number	ADD	Get measured FPS (stub: returns nominal)
setRealtime	(realtime: boolean) => void	DIRECT	Set realtime playback mode
isRealtime	() => boolean	DIRECT	Check if realtime mode is active
setInc	(inc: number) => void	ADD	Set playback direction (1 or -1)
inc	() => number	ADD	Get playback increment
setPlayMode	(mode: number) => void	DIRECT	Set loop mode (0=Loop, 1=Once, 2=PingPong)
playMode	() => number	DIRECT	Get loop mode as integer constant
inPoint	() => number	DIRECT	Get in-point frame
outPoint	() => number	DIRECT	Get out-point frame
setInPoint	(frame: number) => void	DIRECT	Set in-point frame
setOutPoint	(frame: number) => void	DIRECT	Set out-point frame
skipped	() => number	ADD	Skipped frames since last reset
isCurrentFrameIncomplete	() => boolean	ADD	Always returns false
isCurrentFrameError	() => boolean	ADD	Always returns false
isBuffering	() => boolean	ADD	Always returns false
mbps	() => number	ADD	I/O throughput in Mbps
resetMbps	() => void	ADD	Reset throughput counter

Audio

Command	Signature	Status	Description
scrubAudio	(enable: boolean, chunkDuration?: number, loopCount?: number) => void	PARTIAL	Enable/disable audio scrub. chunkDuration and loopCount are ignored.

View & Display

Command	Signature	Status	Description
redraw	() => void	STUB	Request viewport repaint via requestAnimationFrame
viewSize	() => [number, number]	DIRECT	Get canvas size as [width, height]
setViewSize	(w: number, h: number) => void	DIRECT	Set canvas size
resizeFit	() => void	DIRECT	Fit image to viewport
fullScreenMode	(enable: boolean) => void	DIRECT	Enter/exit fullscreen (async internally)
isFullScreen	() => boolean	DIRECT	Check fullscreen state
setWindowTitle	(title: string) => void	DIRECT	Set browser tab title
setFiltering	(mode: number) => void	ADD	Set texture filter (0=Nearest, 1=Linear)
getFiltering	() => number	ADD	Get current filter mode
setBGMethod	(method: string) => void	ADD	Set background method
bgMethod	() => string	ADD	Get background method
setMargins	(margins: number[], relative: boolean) => void	ADD	Set viewport margins
margins	() => number[]	ADD	Get viewport margins
contentAspect	() => number	PARTIAL	Get content aspect ratio (width/height)
devicePixelRatio	() => number	DIRECT	Get device pixel ratio

Frame Marks

Command	Signature	Status	Description
markFrame	(frame: number, marked: boolean) => void	DIRECT	Mark or unmark a frame
isMarked	(frame: number) => boolean	DIRECT	Check if a frame is marked
markedFrames	() => number[]	DIRECT	Get all marked frame numbers

N/A Stubs

These commands exist for API compatibility but log a warning and return defaults. Check with isSupported(name) -- all return false.

Category	Commands
Audio Cache	setAudioCacheMode, audioCacheMode
Window Mgmt	center, close
Stereo	setHardwareStereoMode, stereoSupported
Cache System	setCacheMode, cacheMode, isCaching, cacheInfo, cacheSize, clearAllButFrame, releaseAllUnusedImages, releaseAllCachedImages, flushCacheNodeOutput
Session File	sessionFileName, setSessionFileName
Mu Runtime	eval
File System	contractSequences, sequenceOfFile, existingFilesInSequence
LUT	updateLUT
File Watch	watchFile
Console	showConsole, isConsoleVisible
Renderer	setRendererType
Renderer (partial)	getRendererType -- returns "WebGL2"
Cache Dir	cacheDir
Network Port	myNetworkPort
Security	encodePassword, decodePassword
Video Devices	videoDeviceIDString, refreshOutputVideoDevice, audioTextureID
Qt Widgets	mainWindowWidget, mainViewWidget, prefTabWidget, sessionBottomToolBar, networkAccessManager
Menu Bar	toggleMenuBar, isMenuBarVisible, defineModeMenu
Misc	spoofConnectionStream, setDisplayProfilesFromSettings, associatedVideoDevice, toggleMotionScope, cacheUsage

---

window.rv.extra_commands (MuExtraCommands)

All extra commands delegate to MuCommands or directly to the OpenRV API.

Display Feedback

Command	Signature	Description
displayFeedback	(message, duration?, glyph?, position?) => void	Show a HUD message (logs to console, stores for retrieval)
displayFeedbackQueue	(message, duration?, glyph?, position?) => void	Queue a feedback message
displayFeedback2	(message, duration?) => void	Simple feedback (no glyph/position)
displayFeedbackWithSizes	(message, duration?, sizes?) => void	Feedback with custom font sizes

Session State Queries

Command	Signature	Description
isSessionEmpty	() => boolean	Check if no media is loaded
isNarrowed	() => boolean	Check if in/out points narrow playback range
isPlayable	() => boolean	Check if enough frames to play
isPlayingForwards	() => boolean	Playing forward?
isPlayingBackwards	() => boolean	Playing backward?

Playback Toggles

Command	Signature	Description
togglePlay	() => void	Toggle play/pause
toggleForwardsBackwards	() => void	Toggle playback direction
toggleRealtime	() => void	Toggle realtime mode
toggleFullScreen	() => void	Toggle fullscreen

View Transform

Command	Signature	Description
setScale	(scale: number) => void	Set zoom level
scale	() => number	Get zoom level
setTranslation	([x, y]: [number, number]) => void	Set pan offset
translation	() => [number, number]	Get pan offset
frameImage	() => void	Fit image in viewport

Frame Stepping

Command	Signature	Description
stepForward	(n?: number) => void	Step forward by n frames (default 1)
stepBackward	(n?: number) => void	Step backward by n frames (default 1)
stepForward1	() => void	Step forward 1 frame
stepBackward1	() => void	Step backward 1 frame
stepForward10	() => void	Step forward 10 frames
stepBackward10	() => void	Step backward 10 frames
stepForward100	() => void	Step forward 100 frames
stepBackward100	() => void	Step backward 100 frames

Misc

Command	Signature	Description
numFrames	() => number	Total number of frames
centerResizeFit	() => void	Fit and center image
currentImageAspect	() => number	Current image aspect ratio

---

Bridge Modules

These standalone classes are not mounted on window.rv by default. Import and instantiate them directly from the src/compat/ directory.

MuSourceBridge

Source management bridge providing approximately 27 commands for listing, adding, querying, and modifying media sources. Includes source media queries, display channel names, image source creation, and media representation management.

import { MuSourceBridge } from './compat';

const sources = new MuSourceBridge();
const list = sources.sources();                   // List all source names
const info = sources.sourceMediaInfo('source0');   // Get media info for a source
sources.addSource(['/path/to/media.exr']);           // Add a new source
const size = sources.getCurrentImageSize();        // [width, height]

Key methods: sources, sourcesAtFrame, sourceGeometry, addSource, addSources, addSourceVerbose, addSourceBegin, addSourceEnd, sourceMedia, sourceMediaInfo, sourceMediaInfoList, setSourceMedia, addToSource, relocateSource, sourceAttributes, sourceDataAttributes, sourcePixelValue, sourceDisplayChannelNames, newImageSource, newImageSourcePixels, getCurrentImageSize, clearSession, addSourceMediaRep, setActiveSourceMediaRep

MuPropertyBridge

Typed property store using Mu-style node.component.property dot-path addressing.

import { MuPropertyBridge } from './compat/MuPropertyBridge';

const props = new MuPropertyBridge();

// Create a property
props.newProperty('myNode.color.gain', MuPropertyType.Float, 4);
props.setFloatProperty('myNode.color.gain', [1.0, 1.0, 1.0, 1.0]);

// Read it back
const gain = props.getFloatProperty('myNode.color.gain'); // [1.0, 1.0, 1.0, 1.0]

// Hash shorthand: #TypeName.component.property resolves to first matching node
const value = props.getFloatProperty('#myNode.color.gain');

// Listen for changes
const unsub = props.onPropertyChanged((path, value) => {
  console.log(`${path} changed to`, value);
});

Methods: getFloatProperty, getIntProperty, getHalfProperty, getByteProperty, getStringProperty, setFloatProperty, setIntProperty, setHalfProperty, setByteProperty, setStringProperty, insertFloatProperty, insertIntProperty, insertStringProperty, insertByteProperty, insertHalfProperty, newProperty, newNDProperty, deleteProperty, properties, propertyInfo, propertyExists, onPropertyChanged, setStored, clear, size

MuNodeBridge

Node graph operations wrapping the Graph and NodeFactory.

import { MuNodeBridge } from './compat/MuNodeBridge';

const bridge = new MuNodeBridge(graph);

const name = bridge.newNode('RVColor', 'myColor');
bridge.setNodeInputs(name, ['sourceNode']);
const [inputs, outputs] = bridge.nodeConnections(name);
bridge.setViewNode(name);

Methods: nodes, nodeType, nodeExists, nodesOfType, newNode, deleteNode, nodeConnections, setNodeInputs, testNodeInputs, nodesInGroup, nodeGroup, addNodeToGroup, viewNode, viewNodes, setViewNode, previousViewNode, nextViewNode, addViewableNode, removeViewableNode, nodeImageGeometry

MuEventBridge

Bridges Mu-style event tables and mode system to DOM events.

import { MuEventBridge } from './compat/MuEventBridge';

const events = new MuEventBridge();

// Define a minor mode
events.defineMinorMode('myMode', 10,
  [['key-down--a', (ev) => console.log('A pressed'), 'Handle A key']],
  [], // override bindings
);
events.activateMode('myMode');

// Wire DOM events from a canvas
events.wireDOMEvents(canvasElement);

// Manual event dispatch
events.sendInternalEvent('my-custom-event', 'payload', 'myMode');

// Cleanup
events.dispose();

Methods: bind, bindRegex, unbind, unbindRegex, defineMinorMode, activateMode, deactivateMode, isModeActive, activeModes, pushEventTable, popEventTable, activeEventTables, setEventTableBBox, bindings, bindingDocumentation, sendInternalEvent, wireDOMEvents, dispose

MuEvalBridge

Graph evaluation traversal and image query commands. Provides coordinate transforms between screen/event space and image space, meta-evaluation of the node graph, and rendered image queries.

import { MuEvalBridge } from './compat/MuEvalBridge';

const evalBridge = new MuEvalBridge(graph, nodeBridge);

// Set the current view transform state
evalBridge.setViewTransform({ viewWidth: 1920, viewHeight: 1080, scale: 1, translation: [0, 0], imageWidth: 1920, imageHeight: 1080 });

// Convert event coordinates to image space
const [ix, iy] = evalBridge.eventToImageSpace('source0', [mouseX, mouseY]);

// Query rendered images
const images = evalBridge.renderedImages();

Key methods: metaEvaluate, metaEvaluateClosestByType, closestNodesOfType, mapPropertyToGlobalFrames, renderedImages, imagesAtPixel, imageGeometry, imageGeometryByIndex, imageGeometryByTag, eventToImageSpace, eventToCameraSpace, setViewTransform

ModeManager

Lower-level mode/event-table engine used by MuEventBridge. Supports minor modes with priority ordering, override/global binding tables, and reject/accept event dispatch semantics.

MuNetworkBridge

HTTP requests and remote WebSocket connections.

import { MuNetworkBridge } from './compat/MuNetworkBridge';

const net = new MuNetworkBridge();

// HTTP (returns Promise)
const resp = await net.httpGet('https://example.com/api');
console.log(resp.status, resp.body);

// Remote connections
net.remoteNetwork(true);
net.remoteConnect('peer', 'localhost', 45128);
net.remoteSendEvent('sync-frame', '', '42');

Methods: httpGet, httpPost, httpPut, remoteConnect, remoteDisconnect, remoteSendMessage, remoteSendEvent, remoteSendDataEvent, remoteConnections, remoteApplications, remoteContacts, remoteLocalContactName, setRemoteLocalContactName, remoteNetwork, remoteNetworkStatus, remoteDefaultPermission, setRemoteDefaultPermission, dispose

MuSettingsBridge

Persistent settings backed by localStorage with namespaced keys (openrv-setting:{group}:{key}).

import { MuSettingsBridge } from './compat/MuSettingsBridge';

const settings = new MuSettingsBridge();

settings.writeSetting('ui', 'showTimeline', true);
const show = settings.readSetting('ui', 'showTimeline', false); // true

Methods: readSetting, writeSetting, hasSetting, removeSetting, listSettings, clearGroup, clearAll

MuUtilsBridge

Timers, file kind detection, URL/clipboard, cursor, progressive loading.

import { MuUtilsBridge } from './compat/MuUtilsBridge';

const utils = new MuUtilsBridge();

utils.startTimer();
// ... do work ...
console.log(utils.elapsedTime()); // seconds

utils.fileKind('shot.exr');  // FileKind.ImageFile (1)
utils.setCursor(2);          // pointer cursor
utils.openUrl('https://example.com');

Methods: startTimer, stopTimer, elapsedTime, theTime, isTimerRunning, fileKind, openUrl, putUrlOnClipboard, commandLineFlag, optionsPlay, optionsNoPackages, optionsPlayReset, setCursor, myNetworkHost, loadTotal, loadCount, setProgressiveSourceLoading, progressiveSourceLoading, waitForProgressiveLoading, startPreloadingMedia, setLoadCounters, setWindowTitle, fullScreenMode, isFullScreen, toggleFullScreen, devicePixelRatio

---

Constants

Exported from src/compat/constants.ts and re-exported from the barrel.

import {
  PlayLoop,          // 0
  PlayOnce,          // 1
  PlayPingPong,      // 2
  FilterNearest,     // 0
  FilterLinear,      // 1
  CacheOff,          // 0  (N/A)
  CacheBuffer,       // 1  (N/A)
  CacheGreedy,       // 2  (N/A)
  AudioCacheOff,     // 0  (N/A)
  AudioCacheBuffer,  // 1  (N/A)
  CursorDefault,     // 0
  CursorCrosshair,   // 1
  CursorPointer,     // 2
  CursorWait,        // 3
  CursorText,        // 4
  CursorMove,        // 5
  CursorNotAllowed,  // 6
  CursorHelp,        // 7
  BG_METHODS,        // ['black', 'checker', 'grey18', 'grey50', 'crosshatch']
} from './compat';

Types module also exports FileKind, MuPropertyType, MuPropertyTypeNames, and MuCursor lookup tables.

---

Migration Guide

Playback

// Mu
commands.play();
commands.setFrame(100);
let f = commands.frame();
commands.setPlayMode(PlayLoop);

// JS (identical)
window.rv.commands.play();
window.rv.commands.setFrame(100);
let f = window.rv.commands.frame();
window.rv.commands.setPlayMode(PlayLoop);

Properties

// Mu
commands.setFloatProperty("#RVColor.color.gain", float[] {1.2, 1.0, 0.8, 1.0});
float[] gain = commands.getFloatProperty("#RVColor.color.gain");

// JS
const props = new MuPropertyBridge();
props.newProperty('#RVColor.color.gain', MuPropertyType.Float, 4);
props.setFloatProperty('#RVColor.color.gain', [1.2, 1.0, 0.8, 1.0]);
const gain = props.getFloatProperty('#RVColor.color.gain');

Events and Modes

// Mu
commands.defineMinorMode("myMode", nil, nil,
  [("key-down--a", myHandler, "Do something on A")], ...);
commands.activateMode("myMode");

// JS
const events = new MuEventBridge();
events.defineMinorMode('myMode', 10,
  [['key-down--a', myHandler, 'Do something on A']],
  [],
);
events.activateMode('myMode');

Settings

// Mu
commands.writeSetting("MyPackage", "option", 42);
int val = commands.readSetting("MyPackage", "option", 0);

// JS
const settings = new MuSettingsBridge();
settings.writeSetting('MyPackage', 'option', 42);
const val = settings.readSetting('MyPackage', 'option', 0);

HTTP Requests

// Mu (callback-based)
commands.httpGet(url, headers, myCallback, nil);

// JS (Promise-based)
const resp = await net.httpGet(url, headers);

---

Differences from Desktop OpenRV

Async commands

fullScreenMode() returns a Promise internally (Fullscreen API is async). Most other commands are synchronous. Check with commands.isAsync(name).

HTTP methods on MuNetworkBridge (httpGet, httpPost, httpPut) return Promises instead of using callbacks.

Type handling

• Mu's float[] becomes number[] in JS.
• Mu's int and float are both number.
• Property type is tracked via MuPropertyType constants (Float=0, Int=1, String=2, Byte=3, Half=4).
• Boolean coercion: scrubAudio applies Boolean() to its first argument for safety.

N/A stubs

Commands that depend on desktop-only features (file system, Qt widgets, hardware stereo, Mu eval, cache system) are provided as stubs. They:

• Log a console.warn explaining why they are unavailable
• Return a sensible default (empty string, 0, false, null, or empty array)
• Are registered with support status false

No eval()

commands.eval() (Mu code evaluation) is stubbed. There is no Mu runtime in the browser.

---

Checking Command Support

import { isSupported, getSupportedCommands } from './compat/stubs';

// Single command
isSupported('play');           // true
isSupported('setCacheMode');   // false
isSupported('getRendererType'); // 'partial'

// Instance method on MuCommands
window.rv.commands.isSupported('setFrame'); // true

// List everything
const all = getSupportedCommands(); // Array<[name, true | false | 'partial']>

A status of 'partial' means the command works but with reduced functionality compared to desktop OpenRV (e.g., scrubAudio ignores chunk duration/loop count; getRendererType always returns "WebGL2").

---

Related Pages

• Scripting API -- The core window.openrv API that the compat layer delegates to
• DCC Integration -- WebSocket-based external application control
• Node Graph Architecture -- Understanding the node graph that MuNodeBridge and MuEvalBridge operate on
• Session Compatibility -- RV session file support