@instructure/quiz-interactions/src/components/hotspot/common/Canvas/index.js

A React UI component Library for quiz interaction types.

/** @jsx jsx */
import {Component} from 'react'
import PropTypes from 'prop-types'
import pickBy from 'lodash/pickBy'

import propTypes, {defaultProps} from './propTypes'
import {jsx} from '@instructure/emotion'
import generateComponentTheme from './theme'
import generateStyle from './styles'
import {withStyleOverrides} from '@instructure/quiz-common/util/withStyleOverrides'

@withStyleOverrides(generateStyle, generateComponentTheme)
export default class Canvas extends Component {
  static displayName = 'Canvas'
  static componentId = `Quizzes${this.displayName}`

  static propTypes = {
    ...propTypes,
    realRef: PropTypes.func,
    drawShape: PropTypes.func.isRequired,
    onMouseOut: PropTypes.func,
    onMouseMove: PropTypes.func,
    onDoubleClick: PropTypes.func,
    onClick: PropTypes.func,
    onKeyPress: PropTypes.func,
    onMouseDown: PropTypes.func,
    onMouseUp: PropTypes.func,
    onTouchStart: PropTypes.func,
    onTouchMove: PropTypes.func,
    onTouchEnd: PropTypes.func,
    styles: PropTypes.object,
  }

  static defaultProps = {
    realRef: null,
    onMouseOut: null,
    onMouseMove: null,
    onDoubleClick: null,
    onClick: null,
    onKeyPress: null,
    onMouseDown: null,
    onMouseUp: null,
    onTouchStart: null,
    onTouchMove: null,
    onTouchEnd: null,
    ...defaultProps,
  }

  state = {
    isDrawing: false,
  }

  constructor(props) {
    super(props)
    // these handlers shouldn't change, so set them once per initialization
    this.eventHandlers = {
      onMouseOut: this.onMouseOut,
      ...pickBy(props, (prop, propName) => prop !== null && propName.startsWith('on')),
    }
  }

  componentDidMount() {
    if (this.props.realRef) {
      this.props.realRef(this)
    }
    this.drawShape(this.props.coordinates)
  }

  componentDidUpdate() {
    this.drawShape(this.props.coordinates)

    if (this.isDrawing()) {
      this.canvasElement.focus()
    }
  }

  // ===========
  //   HELPERS
  // ===========

  isDrawing() {
    return this.state.isDrawing
  }

  getInitialCoordinate() {
    return this.props.coordinates[0]
  }

  getLastCoordinate() {
    return this.props.coordinates[this.props.coordinates.length - 1]
  }

  getCurrentCoordinates(e) {
    const x = e.nativeEvent.offsetX
    const y = e.nativeEvent.offsetY
    return {x, y}
  }

  convertTouchCoordinates(touchEvent) {
    const rect = this.canvasElement.getBoundingClientRect()
    const x = touchEvent.changedTouches[0].pageX - rect.left
    const y = touchEvent.changedTouches[0].pageY - rect.top

    const evt = {
      nativeEvent: {
        offsetX: x,
        offsetY: y,
      },
    }

    return evt
  }

  focus() {
    this.canvasElement.focus()
  }

  refCanvas = node => {
    this.canvasElement = node
  }

  // ===========
  //   ACTIONS
  // ===========

  drawShape = coordinates => {
    this.clearCanvas()
    this.props.drawShape(coordinates)
  }

  clearCanvas() {
    const ctx = this.canvasElement.getContext('2d')
    ctx.clearRect(0, 0, this.canvasElement.width, this.canvasElement.height)
  }

  setStrokeStyle(color = this.props.styles.shapeColor) {
    const ctx = this.canvasElement.getContext('2d')
    ctx.lineWidth = 2
    ctx.strokeStyle = color
  }

  setFillStyle(color = this.props.styles.shapeColor) {
    const ctx = this.canvasElement.getContext('2d')
    ctx.globalAlpha = 0.5
    ctx.fillStyle = color
  }

  startDrawing(e) {
    const initialCoordinate = this.getCurrentCoordinates(e)
    this.props.handleSetCoordinates([initialCoordinate], true)
    this.setState({
      isDrawing: true,
    })
  }

  stopDrawing(coordinates) {
    this.props.handleSetCoordinates(coordinates, false)
    this.setState({
      isDrawing: false,
    })
  }

  // ===========
  //   HANDLERS
  // ===========

  onMouseOut = e => {
    // the mouse out event is handled by default as a click/release on the exiting canvas border
    this.props.onMouseOut // eslint-disable-line no-unused-expressions
      ? this.props.onMouseOut(e)
      : e => {}
  }

  // ===========
  //   RENDER
  // ===========

  renderCanvas() {
    if (this.props.readOnly) {
      return <canvas height={this.props.height} ref={this.refCanvas} width={this.props.width} />
    }

    return (
      <canvas
        css={this.props.styles.canvas}
        height={this.props.height}
        ref={this.refCanvas}
        tabIndex="0"
        width={this.props.width}
        onBlur={this.onMouseOut}
        {...this.eventHandlers}
      />
    )
  }

  render() {
    return <div css={this.props.styles.canvasWrapper}>{this.renderCanvas()}</div>
  }
}