Add double-tap zoom functionary to `ZoomableImage` (#6944)
add <div.zoomable-image__margin/> to keep margin of the image on zooming move setting `scrollLeft` and `scrollTop` of container from callback of `setState` to `componentDidUpdate` add 'hammerjs' package for touch gesture detection rewrite `ZoomableImage` using 'hammerjs'shrike
Yuto Tokunaga
Eugen Rochko
parent
4f9136d2d5
commit
5021c4e9ca
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@ -1,16 +1,10 @@
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import React from 'react';
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import PropTypes from 'prop-types';
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import Hammer from 'hammerjs';
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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 DOUBLE_TAP_SCALE = 2;
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const clamp = (min, max, value) => Math.min(max, Math.max(min, value));
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@ -37,83 +31,97 @@ export default class ZoomableImage extends React.PureComponent {
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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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lastScale = null;
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zoomCenter = null;
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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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// register pinch event handlers to the container
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let hammer = new Hammer.Manager(this.container, {
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// required to make container scrollable by touch
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touchAction: 'pan-x pan-y',
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});
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hammer.add(new Hammer.Pinch());
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hammer.on('pinchstart', this.handlePinchStart);
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hammer.on('pinchmove', this.handlePinchMove);
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this.removers.push(() => hammer.off('pinchstart pinchmove'));
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// register tap event handlers
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hammer = new Hammer.Manager(this.image);
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// NOTE the order of adding is also the order of gesture recognition
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hammer.add(new Hammer.Tap({ event: 'doubletap', taps: 2 }));
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hammer.add(new Hammer.Tap());
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// prevent the 'tap' event handler be fired on double tap
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hammer.get('tap').requireFailure('doubletap');
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// NOTE 'tap' and 'doubletap' events are fired by touch and *mouse*
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hammer.on('tap', this.handleTap);
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hammer.on('doubletap', this.handleDoubleTap);
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this.removers.push(() => hammer.off('tap doubletap'));
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}
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componentWillUnmount () {
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this.removeEventListeners();
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}
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componentDidUpdate (prevProps, prevState) {
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if (!this.zoomCenter) return;
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const { x: cx, y: cy } = this.zoomCenter;
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const { scale: prevScale } = prevState;
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const { scale: nextScale } = this.state;
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const { scrollLeft, scrollTop } = this.container;
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// math memo:
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// x = (scrollLeft + cx) / scrollWidth
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// x' = (nextScrollLeft + cx) / nextScrollWidth
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// scrollWidth = clientWidth * prevScale
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// scrollWidth' = clientWidth * nextScale
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// Solve x = x' for nextScrollLeft
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const nextScrollLeft = (scrollLeft + cx) * nextScale / prevScale - cx;
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const nextScrollTop = (scrollTop + cy) * nextScale / prevScale - cy;
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this.container.scrollLeft = nextScrollLeft;
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this.container.scrollTop = nextScrollTop;
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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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// prevent the click event propagated to parent
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e.stopPropagation();
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// the tap event handler is executed at the same time by touch and mouse,
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// so we don't need to execute the onClick handler here
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}
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handlePinchStart = () => {
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this.lastScale = this.state.scale;
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}
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handlePinchMove = e => {
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const scale = clamp(MIN_SCALE, MAX_SCALE, this.lastScale * e.scale);
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this.zoom(scale, e.center);
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}
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handleTap = () => {
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const handler = this.props.onClick;
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if (handler) handler();
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}
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handleDoubleTap = e => {
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if (this.state.scale === MIN_SCALE)
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this.zoom(DOUBLE_TAP_SCALE, e.center);
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else
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this.zoom(MIN_SCALE, e.center);
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}
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zoom (scale, center) {
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this.zoomCenter = center;
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this.setState({ scale });
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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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@ -126,6 +134,18 @@ export default class ZoomableImage extends React.PureComponent {
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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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const marginStyle = {
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position: 'absolute',
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top: 0,
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bottom: 0,
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left: 0,
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right: 0,
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display: 'flex',
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alignItems: 'center',
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justifyContent: 'center',
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transform: `scale(${scale})`,
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transformOrigin: '0 0',
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};
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return (
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<div
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@ -133,17 +153,18 @@ export default class ZoomableImage extends React.PureComponent {
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ref={this.setContainerRef}
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style={{ overflow }}
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>
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<img
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role='presentation'
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ref={this.setImageRef}
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alt={alt}
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src={src}
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style={{
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transform: `scale(${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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className='zoomable-image__margin'
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style={marginStyle}
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>
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<img
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ref={this.setImageRef}
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role='presentation'
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alt={alt}
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src={src}
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onClick={this.handleClick}
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/>
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</div>
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</div>
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);
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}
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@ -1459,9 +1459,6 @@
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position: relative;
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width: 100%;
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height: 100%;
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display: flex;
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align-items: center;
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justify-content: center;
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img {
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max-width: $media-modal-media-max-width;
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@ -54,6 +54,7 @@
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"file-loader": "^0.11.2",
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"font-awesome": "^4.7.0",
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"glob": "^7.1.1",
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"hammerjs": "^2.0.8",
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"http-link-header": "^0.8.0",
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"immutable": "^3.8.2",
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"imports-loader": "^0.8.0",
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@ -3092,6 +3092,10 @@ gzip-size@^3.0.0:
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dependencies:
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duplexer "^0.1.1"
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hammerjs@^2.0.8:
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version "2.0.8"
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resolved "https://registry.yarnpkg.com/hammerjs/-/hammerjs-2.0.8.tgz#04ef77862cff2bb79d30f7692095930222bf60f1"
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handle-thing@^1.2.5:
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version "1.2.5"
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resolved "https://registry.yarnpkg.com/handle-thing/-/handle-thing-1.2.5.tgz#fd7aad726bf1a5fd16dfc29b2f7a6601d27139c4"
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