Align: Space Evenly: Rotate: Z-Order: Arrow Mode: Move Select Scroll Tree None
This example demonstrates a custom CommandHandler. It allows the user to position selected Parts in a diagram relative to each other, overrides CommandHandler.doKeyDown to allow handling the arrow keys in additional manners, and uses a "paste offset" so that pasting objects will cascade them rather than place them on top of one another. It is defined in its own file, as DrawCommandHandler.js.
The above buttons can be used to align Parts, rotate Parts, or change the behavior of the arrow keys.
Usage can also be seen in the BPMN Editor sample.
GoJS can be extended in a variety of ways. The most common way to change the standard behavior is to set properties on the GraphObject, Diagram, CommandHandler, Tool, or Layout. But when the desired property does not exist, you might need to override methods of CommandHandler, Tool, Layout, Link, or Node. Methods that you can override are documented in the API reference. Various features of GoJS can be overriden, either by replacing a method on an instance (a feature of JavaScript) or by defining a subclass. You should not modify the prototypes of any of the GoJS classes.
In addition to our samples, GoJS provides an extensions gallery,
showcasing the creation of custom tools and layouts.
Those classes and samples are written in TypeScript, available at ../extensionsJSM/,
as ECMAScript/JavaScript modules -- these use the ../release/go-module.js library.
We recommend that you copy the files that you need into your project, so that you can adjust how they refer to the GoJS library
that you choose and so that you can include them into your own building and packaging procedures.
More information can be found in the GoJS Intro.
A CommandHandler handles all default keyboard input events in a Diagram. There are many predefined methods on CommandHandler that implement common commands to operate on the Diagram or the current Diagram.selection>.
You can override CommandHandler.doKeyDown to handle additional keyboard shortcuts or to change which commands are invoked via the keyboard.
Your code can invoke a command by calling the appropriate method on the Diagram.commandHandler. Each command method has a corresponding can... predicate that your code can use to enable or disable any buttons that invoke the command. Your code can customize the behavior of a command by overriding the method on CommandHandler, or by setting properties on the CommandHandler or Diagram or Parts -- see GoJS Permissions.
There are several CommandHandler extensions that provide additional functionality.
More information can be found in the GoJS Intro.