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HTML5 Drawing Tool

Demo: https://models-resources.concord.org/drawing-tool/branch/master/examples/index.html

Using as a library

npm install drawing-tool

In myComponent.js:

import DrawingTool from "drawing-tool";
import 'drawing-tool/dist/drawing-tool.css';

const drawingTool = new DrawingTool("#drawing-tool-container");

Development

  • Install (if you don't have them):
  • Run:
    • npm install to install dependencies.
    • webpack --watch -- Automatically compiles sources to ./dist
    • live-server . -- starts a web server on http://localhost:8080/
    • Open http://localhost:8080/examples/.
    • Code!!
    • Before you commit, run webpack to update dist directory and add it to git index.

Undo / redo feature

If you are planning to add new feature that will be exposed in UI or via main API, you should consider whether this action should be saved in history (so undo and redo is possible) or not.

If so, all you need to do is to call DrawingTool.pushToHistory method.

The current convention is that everything that modifies canvas should be saved in history, e.g.:

  • new object created
  • object removed
  • object stroke color changed
  • canvas dimensions changed

However state of the drawing tool itself is not tracked, so e.g. following events are not saved:

  • tool changed
  • current stroke color changed
  • current fill color changed

If an action is async and callback can be provided, callback should be invoked after history is updated (see DrawingTool.setBackgroundImage). It gives us more flexibility, as the client code can reset history after action is complete so user won't be able to undo it (sometimes it is useful).

JSON state converter

Drawing Tool state can be serialized to JSON. If you're introducing non-backward compatible change, update version in DrawingTool#save method and add approperiate conversion to convert-state.js.