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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'
pull/410/head
Yuto Tokunaga 2018-03-29 03:40:51 +09:00 committed by Eugen Rochko
parent 4f9136d2d5
commit 5021c4e9ca
4 changed files with 103 additions and 80 deletions
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163
app/javascript/mastodon/features/ui/components/zoomable_image.js
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@ -1,16 +1,10 @@
import React from 'react';
import PropTypes from 'prop-types';
import Hammer from 'hammerjs';
const MIN_SCALE = 1;
const MAX_SCALE = 4;
const getMidpoint = (p1, p2) => ({
x: (p1.clientX + p2.clientX) / 2,
y: (p1.clientY + p2.clientY) / 2,
});
const getDistance = (p1, p2) =>
Math.sqrt(Math.pow(p1.clientX - p2.clientX, 2) + Math.pow(p1.clientY - p2.clientY, 2));
const DOUBLE_TAP_SCALE = 2;
const clamp = (min, max, value) => Math.min(max, Math.max(min, value));
@ -37,83 +31,97 @@ export default class ZoomableImage extends React.PureComponent {
removers = [];
container = null;
image = null;
lastTouchEndTime = 0;
lastDistance = 0;
lastScale = null;
zoomCenter = null;
componentDidMount () {
let handler = this.handleTouchStart;
this.container.addEventListener('touchstart', handler);
this.removers.push(() => this.container.removeEventListener('touchstart', handler));
handler = this.handleTouchMove;
// on Chrome 56+, touch event listeners will default to passive
// https://www.chromestatus.com/features/5093566007214080
this.container.addEventListener('touchmove', handler, { passive: false });
this.removers.push(() => this.container.removeEventListener('touchend', handler));
// register pinch event handlers to the container
let hammer = new Hammer.Manager(this.container, {
// required to make container scrollable by touch
touchAction: 'pan-x pan-y',
});
hammer.add(new Hammer.Pinch());
hammer.on('pinchstart', this.handlePinchStart);
hammer.on('pinchmove', this.handlePinchMove);
this.removers.push(() => hammer.off('pinchstart pinchmove'));
// register tap event handlers
hammer = new Hammer.Manager(this.image);
// NOTE the order of adding is also the order of gesture recognition
hammer.add(new Hammer.Tap({ event: 'doubletap', taps: 2 }));
hammer.add(new Hammer.Tap());
// prevent the 'tap' event handler be fired on double tap
hammer.get('tap').requireFailure('doubletap');
// NOTE 'tap' and 'doubletap' events are fired by touch and *mouse*
hammer.on('tap', this.handleTap);
hammer.on('doubletap', this.handleDoubleTap);
this.removers.push(() => hammer.off('tap doubletap'));
}
componentWillUnmount () {
this.removeEventListeners();
}
componentDidUpdate (prevProps, prevState) {
if (!this.zoomCenter) return;
const { x: cx, y: cy } = this.zoomCenter;
const { scale: prevScale } = prevState;
const { scale: nextScale } = this.state;
const { scrollLeft, scrollTop } = this.container;
// math memo:
// x = (scrollLeft + cx) / scrollWidth
// x' = (nextScrollLeft + cx) / nextScrollWidth
// scrollWidth = clientWidth * prevScale
// scrollWidth' = clientWidth * nextScale
// Solve x = x' for nextScrollLeft
const nextScrollLeft = (scrollLeft + cx) * nextScale / prevScale - cx;
const nextScrollTop = (scrollTop + cy) * nextScale / prevScale - cy;
this.container.scrollLeft = nextScrollLeft;
this.container.scrollTop = nextScrollTop;
}
removeEventListeners () {
this.removers.forEach(listeners => listeners());
this.removers = [];
}
handleTouchStart = e => {
if (e.touches.length !== 2) return;
this.lastDistance = getDistance(...e.touches);
}
handleTouchMove = e => {
const { scrollTop, scrollHeight, clientHeight } = this.container;
if (e.touches.length === 1 && scrollTop !== scrollHeight - clientHeight) {
// prevent propagating event to MediaModal
e.stopPropagation();
return;
}
if (e.touches.length !== 2) return;
e.preventDefault();
e.stopPropagation();
const distance = getDistance(...e.touches);
const midpoint = getMidpoint(...e.touches);
const scale = clamp(MIN_SCALE, MAX_SCALE, this.state.scale * distance / this.lastDistance);
this.zoom(scale, midpoint);
this.lastMidpoint = midpoint;
this.lastDistance = distance;
}
zoom(nextScale, midpoint) {
const { scale } = this.state;
const { scrollLeft, scrollTop } = this.container;
// math memo:
// x = (scrollLeft + midpoint.x) / scrollWidth
// x' = (nextScrollLeft + midpoint.x) / nextScrollWidth
// scrollWidth = clientWidth * scale
// scrollWidth' = clientWidth * nextScale
// Solve x = x' for nextScrollLeft
const nextScrollLeft = (scrollLeft + midpoint.x) * nextScale / scale - midpoint.x;
const nextScrollTop = (scrollTop + midpoint.y) * nextScale / scale - midpoint.y;
this.setState({ scale: nextScale }, () => {
this.container.scrollLeft = nextScrollLeft;
this.container.scrollTop = nextScrollTop;
});
}
handleClick = e => {
// don't propagate event to MediaModal
// prevent the click event propagated to parent
e.stopPropagation();
// the tap event handler is executed at the same time by touch and mouse,
// so we don't need to execute the onClick handler here
}
handlePinchStart = () => {
this.lastScale = this.state.scale;
}
handlePinchMove = e => {
const scale = clamp(MIN_SCALE, MAX_SCALE, this.lastScale * e.scale);
this.zoom(scale, e.center);
}
handleTap = () => {
const handler = this.props.onClick;
if (handler) handler();
}
handleDoubleTap = e => {
if (this.state.scale === MIN_SCALE)
this.zoom(DOUBLE_TAP_SCALE, e.center);
else
this.zoom(MIN_SCALE, e.center);
}
zoom (scale, center) {
this.zoomCenter = center;
this.setState({ scale });
}
setContainerRef = c => {
this.container = c;
}
@ -126,25 +134,38 @@ export default class ZoomableImage extends React.PureComponent {
const { alt, src } = this.props;
const { scale } = this.state;
const overflow = scale === 1 ? 'hidden' : 'scroll';
const marginStyle = {
position: 'absolute',
top: 0,
bottom: 0,
left: 0,
right: 0,
display: 'flex',
alignItems: 'center',
justifyContent: 'center',
transform: `scale(${scale})`,
transformOrigin: '0 0',
};
return (
<div
className='zoomable-image'
ref={this.setContainerRef}
style={{ overflow }}
>
<div
className='zoomable-image__margin'
style={marginStyle}
>
<img
role='presentation'
ref={this.setImageRef}
role='presentation'
alt={alt}
src={src}
style={{
transform: `scale(${scale})`,
transformOrigin: '0 0',
}}
onClick={this.handleClick}
/>
</div>
</div>
);
}

3
app/javascript/styles/mastodon/components.scss
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@ -1459,9 +1459,6 @@
position: relative;
width: 100%;
height: 100%;
display: flex;
align-items: center;
justify-content: center;
img {
max-width: $media-modal-media-max-width;

1
package.json
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@ -54,6 +54,7 @@
"file-loader": "^0.11.2",
"font-awesome": "^4.7.0",
"glob": "^7.1.1",
"hammerjs": "^2.0.8",
"http-link-header": "^0.8.0",
"immutable": "^3.8.2",
"imports-loader": "^0.8.0",

4
yarn.lock
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@ -3092,6 +3092,10 @@ gzip-size@^3.0.0:
dependencies:
duplexer "^0.1.1"
hammerjs@^2.0.8:
version "2.0.8"
resolved "https://registry.yarnpkg.com/hammerjs/-/hammerjs-2.0.8.tgz#04ef77862cff2bb79d30f7692095930222bf60f1"
handle-thing@^1.2.5:
version "1.2.5"
resolved "https://registry.yarnpkg.com/handle-thing/-/handle-thing-1.2.5.tgz#fd7aad726bf1a5fd16dfc29b2f7a6601d27139c4"