Styles not only provide a visual representation for graph items. They also offer crucial parts for interacting with said items. Hit-testing determines whether a particular item is at a given point in the canvas. It happens all the time during interaction, e.g., when selecting items, moving nodes, or creating edges.
The default implementation in the PortStyleBase class only considers the bounds returned by getBounds when hit-testing. When ports have shapes that deviate from the rectangular bounds, hit-testing has to be adjusted by providing a different implementation for the isHit method.
In this example, we have to adjust the hit-test to the circular port shape. We also take the hit-test radius into account. This radius enables a bit of fuzziness when hit-testing the item, so you can still hit it when you’re slightly outside.
protected isHit(
context: IInputModeContext,
location: Point,
port: IPort
): boolean {
// get the ellipse bounds
const bounds = this.getBounds(context, port)
// use a convenience function to check if the location is inside the ellipse
return GeometryUtilities.ellipseContains(
bounds,
location,
context.hitTestRadius
)
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Note
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Try this implementation by hovering the ports. Notice that the ports at the red node, which uses the default hit-test, also detect hits outside the visual circle within the bounds. The ports at the blue node use the adjusted hit-test code and detect the hover only in the circle. |