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Interactivity

Controlling the Camera​

Out of the box, deck.gl offers viewport controllers that map keyboard, mouse or touch input to camera state change. The easiest way to enable pan/zoom/rotate of the visualization is to set the controller prop on Deck or <DeckGL> to true along with an initialViewState object that defines the initial camera settings:

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

const INITIAL_VIEW_STATE = {
  longitude: -122.4,
  latitude: 37.8,
  zoom: 12,
  pitch: 0,
  bearing: 0
};

const deckInstance = new Deck({
  initialViewState: INITIAL_VIEW_STATE,
  controller: true
});

You can also selectively enable/disable certain controller features:

const deckInstance = new Deck({
  initialViewState: INITIAL_VIEW_STATE,
  controller: {doubleClickZoom: false, touchRotate: true}
});

See Controller for all options.

Reset Camera Position​

An application can reset the camera state by supplying a new initialViewState object at any time:

import {Deck, FlyToInterpolator} from '@deck.gl/core';

const CITIES = {
  SF: {
    longitude: -122.4,
    latitude: 37.8,
    zoom: 10
  },
  NYC: {
    longitude: -74.0,
    latitude: 40.7,
    zoom: 10
  }
}

const deckInstance = new Deck({
  initialViewState: CITIES.SF,
  controller: true
});

for (const button of document.querySelectorAll('button')) {
  button.onclick = () => flyToCity(button.id);
}

function flyToCity(name) {
  deckInstance.setProps({
    initialViewState: {
      ...CITIES[name],
      transitionInterpolator: new FlyToInterpolator({speed: 2}),
      transitionDuration: 'auto'
    }
  })
}

To learn more about animating a view state change, see view state transitions.

Add Constraints to View State​

An application can optionally supply the onViewStateChange callback and manipulate the view state before it is used. The following example constrains the map in a bounding box:

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

const bounds = [
  [-123, 37], // South west corner
  [-122, 38]  // North east corner
];

function applyViewStateConstraints(viewState) {
  return {
    ...viewState,
    longitude: Math.min(bounds[1][0], Math.max(bounds[0][0], viewState.longitude)),
    latitude: Math.min(bounds[1][1], Math.max(bounds[0][1], viewState.latitude))
  };
}

new Deck({
  initialViewState: {
    longitude: -122.4,
    latitude: 37.8,
    zoom: 12
  },
  controller: true,
  onViewStateChange: ({viewState}) => applyViewStateConstraints(viewState)
});

Externally Manage View State​

For more flexibility you can maintain the view state yourself and pass it in to deck.gl via the viewState parameter. This essentially makes Deck/<DeckGL> a stateless component, and allows you to synchronize the view state between multiple components, e.g. via a Redux store. The following example shows the most basic form of doing so.

Note: Do not combine initialViewState and viewState props. viewState will always overwrite any internal state.

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

const deckInstance = new Deck({
  viewState: {
    longitude: -122.4,
    latitude: 37.8,
    zoom: 12
  },
  controller: true,
  onViewStateChange: ({viewState}) => {
    deckInstance.setProps({viewState})
  }
});

Advanced View Controls​

  • Alternative views such as OrbitView, FirstPersonView, and using multiple views such as VR, minimap: Views and Projections
  • Implement a custom controller: Controller

Picking​

Picking is the mechanism through which users interact with the geometries rendered by layers.

deck.gl includes a powerful picking engine that enables the application to precisely determine what object and layer is rendered on a certain pixel on the screen. This picking engine can either be called directly by an application (which is then typically implementing its own event handling), or it can be called automatically by the basic built-in event handling in deck.gl.

What can be Picked?​

The picking engine identifies which object in which layer is at the given coordinates. While usually intuitive, what constitutes a pickable "object" is defined by each layer. Typically, it corresponds to one of the data entries that is passed in via prop.data. For example, in Scatterplot Layer, an object is an element in the props.data array that is used to render one circle. In GeoJson Layer, an object is a GeoJSON feature in the props.data feature collection that is used to render one point, path or polygon.

Because the picking engine uses 8-bit RGBA colors to encode object and layer index, there is a limit of 255 - 1 layers and 255 * 255 * 255 - 1 objects per layer that can be picked at the same time. While deck.gl can easily create more than 254 layers (e.g. with tiled data), the picking process is smart about excluding layers that do not overlap with the queried pixel, so this limit is unlikely a problem in normal circumstances. If your app does hit this limit, it can be circumvented by calling the picking engine directly with multiple batches of layers.

At the moment, the picking mechanism does not work for objects that are offscreen.

Enabling Picking​

Picking can be enabled or disabled on a layer-by-layer basis. To enable picking on a layer, set its pickable prop to true. This value is false by default.

Built-in Events​

For applications that have basic event handling needs, deck.gl has built-in support for handling selected pointer events. When the application registers callbacks, deck.gl automatically tracks these events, runs the picking engine and invokes the callbacks with the resulting PickingInfo object.

The following event handlers are supported:

  • onHover
  • onClick
  • onDragStart
  • onDrag
  • onDragEnd

A event handler function is called with two parameters: info that contains information about the object being interacted with, and event that contains the pointer event.

There are two ways to subscribe to the built-in picking event handling:

import {ScatterplotLayer} from '@deck.gl/layers';

const layer = new ScatterplotLayer({
  data: [
    {position: [-122.45, 37.78]}
  ],
  getPosition: d => d.position,
  getRadius: 1000,
  getFillColor: [255, 255, 0],
  // Required to enable picking
  pickable: true
  // Callback when the pointer enters or leaves an object
  onHover: (info, event) => console.log('Hovered:', info, event),
  // Callback when the pointer clicks on an object
  onClick: (info, event) => console.log('Clicked:', info, event)
});
  • Specify callbacks for all pickable layers by setting event handler props of the Deck/DeckGL component:
import {Deck} from '@deck.gl/core';

new Deck({
  // ...
  // Callback when the pointer enters or leaves an object in any pickable layer
  onHover: (info, event) => console.log('Hovered:', info, event),
  // Callback when the pointer clicks on an object in any pickable layer
  onClick: (info, event) => console.log('Clicked:', info, event)
})

Picking events are triggered based on pickable objects:

  • A click event is triggered every time the pointer clicked on an object in a pickable layer.
  • A hover event is triggered every time the hovered object of a pickable layer changes.

When an event is fired, the onHover or onClick callback of the affected layer is called first. If the callback returns a truthy value, the event is marked as handled. Otherwise, the event will bubble up to the Deck/DeckGL canvas and be visible to its onHover and onClick callbacks.

The PickingInfo Object​

The picking engine returns "picking info" objects which contains a variety of fields describing what layer and object was picked.

KeyTypeValue
pickedbooleanWhether something was found under the pointer. This can be a more reliable test than object because object may be null for certain layer and data types.
indexnumberThe index of the object in the layer that was picked.
layerLayerThe top-level layer that the picked object belongs to. Only layers with the pickable prop set to true can be picked.
sourceLayerLayerThe immediate layer that rendered the picked pixel. This would be different from layer if layer is a CompositeLayer.
objectanyThe object that was picked. This is typically an element from the layer's props.data array, but can vary from layer to layer.
xnumberMouse position x relative to the viewport.
ynumberMouse position y relative to the viewport.
coordinatenumber[]Corresponding point of the mouse position in the coordinate system of the layer. When using the built-in callbacks, this coordinate is 2D, assuming z=0 (i.e. on sea level in a geospatial dataset). You may optionally acquire a 3D position with a performance overhead by calling the picking engine directly.
viewportViewportThe viewport that the picked object belongs to.

Remarks:

  • Specific deck.gl layers, such as the BitmapLayer and TileLayer, may add additional fields to the picking info object. Check the documentation of each layer.
  • Limitation when using multiple views: viewport could potentially be misidentified if two views that contain the picked layer also overlap with each other and do not clear the background.

Example: Display a Tooltip for Hovered Object​

Using the Built-In Tooltip​

Deck automatically renders a tooltip if the getTooltip callback is supplied:

import {Deck} from '@deck.gl/core';
import {ScatterplotLayer} from '@deck.gl/layers';

// Callback to populate the default tooltip with content
function getTooltip({object}) {
  return object && object.message;
}

const deckInstance = new Deck({
  initialViewState: {
    longitude: -122.45,
    latitude: 37.78,
    zoom: 12
  },
  controller: true,
  layers: [
    new ScatterplotLayer({
      data: [
        {position: [-122.45, 37.78], message: 'Hover over me'}
      ],
      getPosition: d => d.position,
      getRadius: 1000,
      getFillColor: [255, 255, 0],
      // Required to enable picking
      pickable: true
    })
  ],
  getTooltip
});

It receives a picking info object and returns the content of the tooltip. To customize the tooltip further, return an object instead:

function getTooltip({object}) {
  return object && {
    html: `<h2>Message:</h2> <div>${object.message}</div>`,
    style: {
      backgroundColor: '#f00',
      fontSize: '0.8em'
    }
  };
}

For a range of options, see getTooltip documentation.

Rendering a Custom Tooltip​

import {Deck} from '@deck.gl/core';
import {ScatterplotLayer} from '@deck.gl/layers';

const tooltip = document.createElement('div');
tooltip.style.position = 'absolute';
tooltip.style.zIndex = 1;
tooltip.style.pointerEvents = 'none';
document.body.append(tooltip);

function updateTooltip({object, x, y}) {
  if (object) {
    tooltip.style.display = 'block';
    tooltip.style.left = `${x}px`;
    tooltip.style.top = `${y}px`;
    tooltip.innerText = object.message;
  } else {
    tooltip.style.display = 'none';
  }
}

const deckInstance = new Deck({
  initialViewState: {
    longitude: -122.45,
    latitude: 37.78,
    zoom: 12
  },
  controller: true,
  layers: [
    new ScatterplotLayer({
      data: [
        {position: [-122.45, 37.78], message: 'Hover over me'}
      ],
      getPosition: d => d.position,
      getRadius: 1000,
      getFillColor: [255, 255, 0],
      // Required to enable picking
      pickable: true,
      // Update tooltip position and content
      onHover: updateTooltip
    })
  ]
});

Calling the Picking Engine Directly​

While the default events handle most of the use cases, sometimes applications need more control over when and how picking is performed.

The picking engine is exposed through the Deck.pickObject and Deck.pickObjects methods. These methods allow you to query what layers and objects within those layers are under a specific point or within a specified rectangle. They return PickingInfo objects as described above.

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

const deckInstance = new Deck({
  // ...
  onClick: ({x, y}) => {
    // Query up to 5 overlapping objects under the pointer
    const pickInfos = deckInstance.pickMultipleObjects({x, y, radius: 1, depth: 5});
    console.log(pickInfo);
  }
});

Also note that by directly calling queryObject, integrating deck.gl into an existing application often becomes easier since you don't have to change the application's existing approach to event handling.

Under The Hood​

If you are using the core layers, all has been taken care of.

If you are implementing a custom layer, read more about how picking is implemented.