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Widget Class

A widget is a UI component that can interact with deck.gl's cameras and layers. Some examples are:

  • A tooltip that follows the pointer and provide information for the hovered object
  • A marker pinned to a geo-location containing HTML content
  • Buttons to manipulate the camera, such as +/- zoom buttons, a compass rose for the MapView, a gimble widget for the OrbitView, etc.
  • A legend that offers visual comparison of sizes, colors etc. corresponding to the rendered layers and viewport. For example a distance ruler, a color scale for the HeatmapLayer, etc.

You may find many ready-to-use widgets in the @deck.gl/widgets module.

A widget is expected to implement the Widget interface. Here is a custom widget that shows a spinner while layers are loading:

import {Widget} from '@deck.gl/core';

class LoadingIndicator implements Widget {
  element?: HTMLDivElement;
  size: number;

  constructor(options: {
    size: number;
  }) {
    this.size = options.size;
  }

  onAdd() {
    const el = document.createElement('div');
    el.className = 'spinner';
    el.style.width = `${this.size}px`;
    // TODO - create animation for .spinner in the CSS stylesheet
    this.element = el;
    return el;
  }

  onRemove() {
    this.element = undefined;
  }

  onRedraw({layers}) {
    const isVisible = layers.some(layer => !layer.isLoaded);
    this.element.style.display = isVisible ? 'block' : 'none';
  }
}

deckgl.addWidget(new LoadingIndicator({size: 48}));

Widget Interface​

When a widget instance is added to Deck, the user can optionally specify a viewId that it is attached to (default null). If assigned, this widget will only respond to events occured inside the specific view that matches this id.

Members​

A Widget implements the following members.

id​

Unique identifier of the widget.

props (object)​

Any options for the widget, as passed into the constructor and can be updated with setProps.

viewId (string | null)​

  • Default: null

The id of the view that the widget is attached to. If null, the widget receives events from all views. Otherwise, it only receives events from the view that matches this id.

placement (string, optional)​

  • Default: 'top-left'

Widget positioning within the view. One of:

  • 'top-left'
  • 'top-right'
  • 'bottom-left'
  • 'bottom-right'
  • 'fill'

Methods​

onAdd​

Required. Called when the widget is added to a Deck instance.

Receives the following arguments:

  • context (object)
    • deck (Deck) - the Deck instance that this widget is being attached to.
    • viewId (string | null) - the view id that this widget is being attached to.

Returns an optional UI element that should be appended to the Deck container.

onRemove​

Required. Called when the widget is removed.

setProps​

Optional. Called to update widget options.

onViewportChange​

Op†ional. Called when the containing view is changed. If viewId: null, will be called if any viewport changes.

Receives the following arguments:

  • viewport (Viewport) - the viewport that has changed

onRedraw​

Optional. Called when the containing view is redrawn. If viewId: null, will be called if anything redraws.

Receives the following arguments:

  • params
    • viewports (Viewport[]) - the viewports that are being redrawn
    • layers (Layer[]) - the layers that are being redrawn

onHover​

Optional. Called when a hover event occurs in the containing view. If viewId: null, will be called if hover occurs in any view.

Receives arguments:

  • info - the picking info describing the object being hovered.
  • event - the original gesture event

onClick​

Optional. Called when a click event occurs in the containing view. If viewId: null, will be called if click occurs in any view.

Receives arguments:

  • info - the picking info describing the object being clicked.
  • event - the original gesture event

onDragStart​

Optional. Called when a dragstart event occurs in the containing view. If viewId: null, will be called if drag occurs in any view.

Receives arguments:

  • info - the picking info describing the object being dragged.
  • event - the original gesture event

onDrag​

Optional. Called when a drag event occurs in the containing view. If viewId: null, will be called if drag occurs in any view.

Receives arguments:

  • info - the picking info describing the object being dragged.
  • event - the original gesture event

onDragEnd​

Optional. Called when a dragend event occurs in the containing view. If viewId: null, will be called if drag occurs in any view.

Receives arguments:

  • info - the picking info describing the object being dragged.
  • event - the original gesture event