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Whiteboard App

Introduction

This version of Whiteboard offers a simple implementation of collaborative drawing. Unlike Ploma, this whiteboard does not implement a local (speculative) drawing nor curve smoothing.

Code Organization

whiteboard.js is the core of the application. Notice that it has some logic to load old persistent data from a previous implementaion.

Invoking Whilteboard

While running the whiteboard app does not require Node or Npm; having them installed on your computer in general helps.

First, you need to copy or install two library files. If you already have Node.js and Npm installed, you can run:

npm run setup

to download following two files. If your system does not have curl, you can open the unpkg URLs specified below in a web browser, and save the js files under the specified names.

If you don't have npm, manually copy three files.

  1. Download croquet.min.js

    curl -L -o croquet/croquet.min.js https://unpkg.com/@croquet/croquet

  2. Download croquet-virtual-dom.js

    curl -L -o croquet/croquet-virtual-dom.js https://unpkg.com/@croquet/virtual-dom

Those files are downloaded to your local disk to allow local development described below.

  1. Add your Croquet API key to apiKey.js Obtain your apiKey from Croquet Dev Portal, create apiKey.js by copying apiKey.js-example to apiKey.js, and insert the key into it.

    const apiKey = "<insert your apiKey from croquet.io/keys>";
export default apiKey;

  2. If you have node installed you can use the simple server implementation:

    node server.js

Otherwise, use your own server for local development, or upload the directory to a server.

Development and Debugging

Developing whiteboard does not involve any build or transpilation process. Just edit the file and reload the page. All Croquet Virtual DOM applications work this way.

Adjusting CSS or view side event handling can involve a lot of iterative development. To speed up browser reloads, you can add ?isLocal to the URL (i.e., localhost:8000/?isLocal) to skip the actual Croquet network initialization. This flag uses an emulated reflector for a single node impelemented in the Virtual DOM Framework. In other words, you can develop the "single user" aspects of the whiteboard app totally offline in this way.

Debugging

You can set a breakpoint in code to see what the application is doing. You can certainly insert the debugger statement in a JS file. Note, however, that the expander code (most of .js files in the /src/ directory) are stringified and then evaluated at runtime. It means that the file you navigate to from the Sources tab of the Chrome Development Tool is not the actual code that the browser is running. If you would like to set a break point in a running code, see the source file display in the console:

where in this example showing file as VM197, VM348, etc. and click on it. Then the expander code that produced the console log can be accessed, and you can insert a break point.