How to get started developing plug-ins

FYI, MuseScore 4.4 (currently nightly master) does plugins slightly differently. It uses qt 6.2.4. I’ll look for the link, but some things done in prior versions no longer work.

I think it best to have an idea of what your plug-in should do, and then suggestions can be focused around the ways to accomplish it, or which plugins can be used to learn how to do something similar.

The 3.0 API is here:
https://musescore.github.io/MuseScore_PluginAPI_Docs/plugins/html/index…

The plug-in creator in version 3 (!) is pretty useful. I would suggest loading musescore 3.7 and using the creator in it to get used to plugins. They can’t all be transferred but you will have learned quite a bit.

I’ll edit a plug-in that has a basic structure. You can then type it in a text editor, save it in the plugs in directory, restart musescore to find it, go to manage plugins to add it into musescore, and then run it from the menu.

It will probably take a couple of days to get to it.

When you said developer’s page, did you mean this?

https://musescore.org/en/handbook/developers-handbook/plugins-3x

This section within may be a good start, for an overview of what is possible:
https://musescore.org/en/node/320673

Source code for 3.7 pre-installed plugins can be found here:
https://github.com/Jojo-Schmitz/MuseScore/tree/3.x/share/plugins

You could start with this one:
https://github.com/Jojo-Schmitz/MuseScore/blob/3.x/share/plugins/helloq…
and ask questions in this thread for clarifications. Then work your way through them.

It would be nice to have a Dummies Guide to MuseScore plugins but there isn't one that I know of.

There are some basic plugins that could work across musescore 3.6 to 4.4, but some controls will not.

In any case, here are what “I think” are the controls for musescore 4.4 using qt 6.2.4.

https://doc.qt.io/qt-6.2/qtquick-controls2-qmlmodule.html

Some are the same name under qt 5.15 and some are not.

The very basic “idea” of a plug-in is to A) load additional capabilities (like import MuseScore 3.0, import QtQuick.Controls 2.2, etc. )
B) set up “global” variables
C) have user interface definitions to build buttons, check boxes, etc.
D) have an optional “on load” section, which can set up things when musescore starts up and initially loads the plug-in into memory and E) “on run”, which is executed when the plug in is run from the menu and F) commands and functions that are linked to structures (like buttons) that run when the button is pressed, that act on and change musescore data structures (by setting values, running built in functions, navigating within the structure, etc.).

There are more capabilities but that is the general idea. Maybe someone can refine the explanation and post their version.

Plug-ins use a limited version of QML. If you see a QML function on a website, don’t be surprised when it doesn’t work. This QML “mostly” uses an object-oriented “variant” data type. Variables are “mostly” of a type based on usage but will sometimes surprise you. Console.log output helps show you what you are looking at. (There are some advance capabilities as well.)

Some data structure are a “fraction” (time signature numerator and denominator for example) and need a method to separate them, a “function” that returns a value (a parameter may be needed to run the function), and arrays and lists (like annotations). Arrays and lists have a “.length”, which will tell how many objects are in them.

Some big structures are staffs. There is a staff index since a score can have multiple staffs. Each staff can have 4 voices. The voice number is set to allow you to work on a particular voice. Inside the staff are measures, etc.

The parent of the staffs is the score. There are variables and functions related to the overall score here. The parent CurScore allows you to navigate through staffs, measures, etc. Then, you can act on them. Navigation can be done multiple - somewhat independent - ways. For instance, go to the next measure, go to a certain “tick” in the score, go to start, go to selection point and access data through the selection, etc.

Looking at the API that I posted earlier gives a better idea of the structures and the related functions.

There is a post somewhere which tells how to view the console in a Windows system. If you don't have a console view, you don't have error messages and console output. It would seem almost impossible to develop a plugin (without MS 3.x plugin creator) without the console.

In any case, use a text editor and enter the plugin below, and name the file 'test.qml'.
Then, use the standard plugin info. For MS3, you want the "Plugins." prefix to the menuPath, or your plugin name won't be in the plugins folder to run plugins. The plugin runs on MS 3.6, 4.2 and 4.4 versions. (sorry, posting removed all indentation).

Run the executable using the "-d" switch (in MS 4+).

// plugin start...
import MuseScore 3.0
import QtQuick 2.1
import QtQuick.Controls 2.1
import QtQuick.Layouts 1.2

MuseScore {
version: "1.0"
id: window
menuPath: "Plugins.MS3MenuName"
description: "My Description-a"

requiresScore: false
pluginType: "dialog"

width: 200
height: 300
visible: true

property int globalVariable: 10
property var globalVar: 5

Component.onCompleted: { // optional for 4.2, but useful to test in all versions
console.log ("plugin loading completed");
if (mscoreMajorVersion >= 4) {
if (mscoreMinorVersion >= 4) {
// VERY STRICT syntax: "title:", with no space between 'title' and ':'
title: "Title for MS4.4+ "
} else {
var tString = "Title for MS4.0 to 4.3x "
title=qsTr(tString);
}
} else {

  }

}

function myFun(a,b) {
return (a+b)
}

onRun:{
// console log doesn't show in the application, only on the terminal when
// using -d option.
console.log ("We're running");
globalVar = globalVar + "A";
globalVariable += 3;
myFun (1,3); // Oh, didn't look at return value
console.log ("myFun test #1: " + myFun(11,43));
console.log ("myFun test #2: " + myFun("AB","CD"));
for (var i = 1; i < 4; i++) {
console.log ("var i is: " + i);
}
}

Column {
Text {
id: refText;
font.pixelSize: 14
text: "hello world!";
}

Button {
id: button4Text;
text: 'Add text'
visible: true
onClicked: {
refText.text = "goodbye!"
}
}
Button {
id: button4Number;
text: 'Show number +1'
visible: true
onClicked: {
globalVariable += 1;
refText.text = globalVariable;
}
}
Button {
id: button4TShowHide;
text: 'Hide/Show buttons'
visible: true
onClicked: {
button4Text.visible = !button4Text.visible;
button4Number.visible = !button4Number.visible;
}
}
Button {
text: 'close';
visible: true;
onClicked: {
(typeof(quit)==='undefined' ? Qt.quit(): quit());
}
}
}
} // end MuseScore