react-map-gl/src/components/draggable-control.js

A React wrapper for MapboxGL-js and overlay API.

// @flow
// Copyright (c) 2015 Uber Technologies, Inc.

// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:

// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.

// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
import PropTypes from 'prop-types';
import BaseControl from './base-control';

import type {MjolnirEvent} from 'mjolnir.js';
import type {BaseControlProps} from './base-control';

const propTypes = Object.assign({}, BaseControl.propTypes, {
  draggable: PropTypes.bool,
  onDrag: PropTypes.func,
  onDragEnd: PropTypes.func,
  onDragStart: PropTypes.func,
  // Offset from the left
  offsetLeft: PropTypes.number,
  // Offset from the top
  offsetTop: PropTypes.number
});

const defaultProps = Object.assign({}, BaseControl.defaultProps, {
  draggable: false,
  offsetLeft: 0,
  offsetTop: 0
});

type Coordinate = [number, number];
type Offset = [number, number];
type CallbackEvent = MjolnirEvent & {
  lngLat: Coordinate
};

export type DraggableControlProps = BaseControlProps & {
  draggable: boolean,
  onDrag?: CallbackEvent => any,
  onDragEnd?: CallbackEvent => any,
  onDragStart?: CallbackEvent => any,
  offsetLeft: number,
  offsetTop: number
};

type State = {
  dragPos: ?Coordinate,
  dragOffset: ?Offset
};

export default class DraggableControl<Props: DraggableControlProps> extends BaseControl<
  Props,
  State,
  HTMLDivElement
> {
  static propTypes = propTypes;
  static defaultProps = defaultProps;

  state = {
    dragPos: null,
    dragOffset: null
  };

  _dragEvents: any = null;

  componentWillUnmount() {
    super.componentWillUnmount();
    this._removeDragEvents();
  }

  _setupDragEvents() {
    const {eventManager} = this._context;
    if (!eventManager) {
      return;
    }

    // panstart is already attached by parent class BaseControl,
    // here we just add listeners for subsequent drag events
    this._dragEvents = {
      panmove: this._onDrag,
      panend: this._onDragEnd,
      pancancel: this._onDragCancel
    };
    eventManager.on(this._dragEvents);
  }

  _removeDragEvents() {
    const {eventManager} = this._context;
    if (!eventManager || !this._dragEvents) {
      return;
    }
    eventManager.off(this._dragEvents);
    this._dragEvents = null;
  }

  _getDragEventPosition(event: MjolnirEvent): Coordinate {
    const {
      offsetCenter: {x, y}
    } = event;
    return [x, y];
  }

  /**
   * Returns offset of top-left of marker from drag start event
   * (used for positioning marker relative to next mouse coordinates)
   */
  _getDragEventOffset(event: MjolnirEvent): ?Offset {
    const {
      center: {x, y}
    } = event;
    const container = this._containerRef.current;
    if (container) {
      const rect = container.getBoundingClientRect();
      return [rect.left - x, rect.top - y];
    }
    return null;
  }

  _getDraggedPosition(dragPos: Coordinate, dragOffset: Offset): Coordinate {
    return [dragPos[0] + dragOffset[0], dragPos[1] + dragOffset[1]];
  }

  _getDragLngLat(dragPos: Coordinate, dragOffset: Offset): Coordinate {
    const {offsetLeft, offsetTop} = this.props;
    const [x, y] = this._getDraggedPosition(dragPos, dragOffset);
    // Unproject x/y value while respecting offset coordinates
    return this._context.viewport.unproject([x - offsetLeft, y - offsetTop]);
  }

  _onDragStart = (event: MjolnirEvent) => {
    const {draggable, captureDrag} = this.props;
    if (draggable || captureDrag) {
      event.stopPropagation();
    }
    if (!draggable) {
      return;
    }

    const dragPos = this._getDragEventPosition(event);
    const dragOffset = this._getDragEventOffset(event);
    this.setState({dragPos, dragOffset});
    this._setupDragEvents();

    const {onDragStart} = this.props;
    if (onDragStart && dragOffset) {
      const callbackEvent: CallbackEvent = Object.assign({}, event);
      callbackEvent.lngLat = this._getDragLngLat(dragPos, dragOffset);
      onDragStart(callbackEvent);
    }
  };

  _onDrag = (event: MjolnirEvent) => {
    event.stopPropagation();

    const dragPos = this._getDragEventPosition(event);
    this.setState({dragPos});

    const {onDrag} = this.props;
    const {dragOffset} = this.state;
    if (onDrag && dragOffset) {
      const callbackEvent: CallbackEvent = Object.assign({}, event);
      callbackEvent.lngLat = this._getDragLngLat(dragPos, dragOffset);
      onDrag(callbackEvent);
    }
  };

  _onDragEnd = (event: MjolnirEvent) => {
    const {dragPos, dragOffset} = this.state;

    event.stopPropagation();
    this.setState({dragPos: null, dragOffset: null});
    this._removeDragEvents();

    const {onDragEnd} = this.props;
    if (onDragEnd && dragPos && dragOffset) {
      const callbackEvent: CallbackEvent = Object.assign({}, event);
      callbackEvent.lngLat = this._getDragLngLat(dragPos, dragOffset);
      onDragEnd(callbackEvent);
    }
  };

  _onDragCancel = (event: MjolnirEvent) => {
    event.stopPropagation();
    this.setState({dragPos: null, dragOffset: null});
    this._removeDragEvents();
  };
}