Thibaut Girka
6 years ago
parent
0b86ec4e7f
commit
87071d9e81
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import React from 'react'; |
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import PropTypes from 'prop-types'; |
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const MIN_SCALE = 1; |
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const MAX_SCALE = 4; |
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const getMidpoint = (p1, p2) => ({ |
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x: (p1.clientX + p2.clientX) / 2, |
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y: (p1.clientY + p2.clientY) / 2, |
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}); |
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const getDistance = (p1, p2) => |
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Math.sqrt(Math.pow(p1.clientX - p2.clientX, 2) + Math.pow(p1.clientY - p2.clientY, 2)); |
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const clamp = (min, max, value) => Math.min(max, Math.max(min, value)); |
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export default class ZoomableImage extends React.PureComponent { |
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static propTypes = { |
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alt: PropTypes.string, |
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src: PropTypes.string.isRequired, |
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width: PropTypes.number, |
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height: PropTypes.number, |
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onClick: PropTypes.func, |
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} |
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static defaultProps = { |
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alt: '', |
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width: null, |
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height: null, |
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}; |
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state = { |
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scale: MIN_SCALE, |
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} |
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removers = []; |
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container = null; |
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image = null; |
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lastTouchEndTime = 0; |
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lastDistance = 0; |
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componentDidMount () { |
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let handler = this.handleTouchStart; |
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this.container.addEventListener('touchstart', handler); |
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this.removers.push(() => this.container.removeEventListener('touchstart', handler)); |
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handler = this.handleTouchMove; |
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// on Chrome 56+, touch event listeners will default to passive
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// https://www.chromestatus.com/features/5093566007214080
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this.container.addEventListener('touchmove', handler, { passive: false }); |
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this.removers.push(() => this.container.removeEventListener('touchend', handler)); |
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} |
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componentWillUnmount () { |
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this.removeEventListeners(); |
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} |
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removeEventListeners () { |
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this.removers.forEach(listeners => listeners()); |
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this.removers = []; |
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} |
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handleTouchStart = e => { |
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if (e.touches.length !== 2) return; |
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this.lastDistance = getDistance(...e.touches); |
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} |
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handleTouchMove = e => { |
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const { scrollTop, scrollHeight, clientHeight } = this.container; |
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if (e.touches.length === 1 && scrollTop !== scrollHeight - clientHeight) { |
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// prevent propagating event to MediaModal
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e.stopPropagation(); |
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return; |
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} |
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if (e.touches.length !== 2) return; |
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e.preventDefault(); |
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e.stopPropagation(); |
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const distance = getDistance(...e.touches); |
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const midpoint = getMidpoint(...e.touches); |
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const scale = clamp(MIN_SCALE, MAX_SCALE, this.state.scale * distance / this.lastDistance); |
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this.zoom(scale, midpoint); |
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this.lastMidpoint = midpoint; |
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this.lastDistance = distance; |
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} |
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zoom(nextScale, midpoint) { |
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const { scale } = this.state; |
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const { scrollLeft, scrollTop } = this.container; |
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// math memo:
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// x = (scrollLeft + midpoint.x) / scrollWidth
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// x' = (nextScrollLeft + midpoint.x) / nextScrollWidth
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// scrollWidth = clientWidth * scale
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// scrollWidth' = clientWidth * nextScale
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// Solve x = x' for nextScrollLeft
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const nextScrollLeft = (scrollLeft + midpoint.x) * nextScale / scale - midpoint.x; |
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const nextScrollTop = (scrollTop + midpoint.y) * nextScale / scale - midpoint.y; |
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this.setState({ scale: nextScale }, () => { |
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this.container.scrollLeft = nextScrollLeft; |
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this.container.scrollTop = nextScrollTop; |
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}); |
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} |
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handleClick = e => { |
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// don't propagate event to MediaModal
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e.stopPropagation(); |
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const handler = this.props.onClick; |
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if (handler) handler(); |
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} |
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setContainerRef = c => { |
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this.container = c; |
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} |
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setImageRef = c => { |
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this.image = c; |
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} |
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render () { |
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const { alt, src } = this.props; |
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const { scale } = this.state; |
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const overflow = scale === 1 ? 'hidden' : 'scroll'; |
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return ( |
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<div |
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className='zoomable-image' |
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ref={this.setContainerRef} |
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style={{ overflow }} |
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> |
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<img |
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role='presentation' |
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ref={this.setImageRef} |
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alt={alt} |
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src={src} |
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style={{ |
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transform: `scale(${scale})`, |
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transformOrigin: '0 0', |
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}} |
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onClick={this.handleClick} |
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/> |
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</div> |
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); |
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} |
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} |
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