import React from 'react';
import PropTypes from 'prop-types';
-import Hammer from 'hammerjs';
const MIN_SCALE = 1;
const MAX_SCALE = 4;
-const DOUBLE_TAP_SCALE = 2;
+
+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 clamp = (min, max, value) => Math.min(max, Math.max(min, value));
removers = [];
container = null;
image = null;
- lastScale = null;
- zoomCenter = null;
+ lastTouchEndTime = 0;
+ lastDistance = 0;
componentDidMount () {
- // 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'));
+ 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));
}
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 = [];
}
- handleClick = e => {
- // prevent the click event propagated to parent
- e.stopPropagation();
+ handleTouchStart = e => {
+ if (e.touches.length !== 2) return;
- // 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
+ this.lastDistance = getDistance(...e.touches);
}
- handlePinchStart = () => {
- this.lastScale = this.state.scale;
- }
+ 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;
- handlePinchMove = e => {
- const scale = clamp(MIN_SCALE, MAX_SCALE, this.lastScale * e.scale);
- this.zoom(scale, e.center);
- }
+ e.preventDefault();
+ e.stopPropagation();
- handleTap = () => {
- const handler = this.props.onClick;
- if (handler) handler();
+ 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;
}
- handleDoubleTap = e => {
- if (this.state.scale === MIN_SCALE)
- this.zoom(DOUBLE_TAP_SCALE, e.center);
- else
- this.zoom(MIN_SCALE, e.center);
+ 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;
+ });
}
- zoom (scale, center) {
- this.zoomCenter = center;
- this.setState({ scale });
+ handleClick = e => {
+ // don't propagate event to MediaModal
+ e.stopPropagation();
+ const handler = this.props.onClick;
+ if (handler) handler();
}
setContainerRef = c => {
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(${scale})`,
- transformOrigin: '0 0',
- };
return (
<div
ref={this.setContainerRef}
style={{ overflow }}
>
- <div
- className='zoomable-image__margin'
- style={marginStyle}
- >
- <img
- ref={this.setImageRef}
- role='presentation'
- alt={alt}
- src={src}
- onClick={this.handleClick}
- />
- </div>
+ <img
+ role='presentation'
+ ref={this.setImageRef}
+ alt={alt}
+ src={src}
+ style={{
+ transform: `scale(${scale})`,
+ transformOrigin: '0 0',
+ }}
+ onClick={this.handleClick}
+ />
</div>
);
}
cat aescling's git repositories / mastodon.git / commitdiff