README.md

Command Palette

Register commands in the Command Palette.

One major concept of the Lumino library on which JupyterLab is built is the notion of Commands as explained in the commands example.

Commands can be used from the command palette.

In this extension, you are going to add a command to the command palette.

The command palette interface ICommandPalette need to be imported with:

// src/index.ts#L6-L6

import { ICommandPalette } from '@jupyterlab/apputils';

To see how you can add the command to the palette, let's have a look at src/index.ts.

// src/index.ts#L11-L36

const extension: JupyterFrontEndPlugin<void> = {
  id: 'command-palette',
  description:
    'Minimal JupyterLab example adding a new command to the palette.',
  autoStart: true,
  requires: [ICommandPalette],
  activate: (app: JupyterFrontEnd, palette: ICommandPalette) => {
    const { commands } = app;

    const command = 'jlab-examples:command-palette';

    // Add a command
    commands.addCommand(command, {
      label: 'Execute jlab-examples:command-palette Command',
      caption: 'Execute jlab-examples:command-palette Command',
      execute: (args: any) => {
        console.log(
          `jlab-examples:command-palette has been called ${args['origin']}.`
        );
      }
    });

    // Add the command to the command palette
    const category = 'Extension Examples';
    palette.addItem({ command, category, args: { origin: 'from palette' } });
  }

The ICommandPalette (documentation) is passed to the activate function as an argument (variable palette) in addition to the JupyterLab application (variable app).

You should request that dependency with the property requires: [ICommandPalette],. It lists the additional arguments you want to inject into the activate function in the JupyterFontEndPlugin.

ICommandPalette provides the method addItem that links a palette entry to a command in the command registry.

It requires two arguments: the unique command id and the command category (that can be either an existing category or a new one). And optionally, you can specify the arguments that will be passed to the command when executed from the palette.

When running JupyterLab with this extension, a message should appear in the web browser console after clicking on the command in the palette.

Where to Go Next

A command can be triggered by other UI elements:

• Add the command to a menu
• Add the command to the launcher