This sample demonstrates the PolylineLinkingTool, which replaces the standard LinkingTool. The tool is defined in its own file, as PolylineLinkingTool.js.

The user starts drawing a new link from a node in the normal manner, by dragging from a port, which for feedback purposes has a "pointer" cursor. Normally the user would have to release the mouse near the target port/node. However with the PolylineLinkingTool the user may click at various points to cause the new link to be routed along those points. Clicking on the target port completes the new link. Press Escape to cancel, or Z to remove the last point.

Furthermore, because Link.resegmentable is true, the user can easily add or remove segments from the route of a selected link. To insert a segment, the user can start dragging the small diamond resegmenting handle. To remove a segment, the user needs to move a regular reshaping handle to cause the adjacent two segments to be in a straight line.

The PolylineLinkingTool also works with orthogonally routed links. To demonstrate this, uncomment the two lines that initialize Link.routing to be Routing.Orthogonal.

GoJS Features in this sample


The Link class is used to implement a visual relationship between nodes. Links are normally created by the presence of link data objects in the GraphLinksModel.linkDataArray or by a parent key reference as the value of the TreeModel.nodeParentKeyProperty of a node data object in a TreeModel. More information can be found in the GoJS Intro.

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Tools handle all input events, such as mouse and keyboard interactions, in a Diagram. There are many kinds of predefined Tool classes that implement all of the common operations that users do.

For flexibility and simplicity, all input events are canonicalized as InputEvents and redirected by the diagram to go to the Diagram.currentTool. By default the Diagram.currentTool is an instance of ToolManager held as the Diagram.toolManager. The ToolManager implements support for all mode-less tools. The ToolManager is responsible for finding another tool that is ready to run and then making it the new current tool. This causes the new tool to process all of the input events (mouse, keyboard, and touch) until the tool decides that it is finished, at which time the diagram's current tool reverts back to the Diagram.defaultTool, which is normally the ToolManager, again.

More information can be found in the GoJS Intro.

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GoJS Extensions

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.

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