[RFC] Improved media modal (#5956)

* Improved media modal

ImageLoader: Impliment pinch zoom by CSS `transform: scale(X)`
ImageLoader: Impliment panning by CSS `overflow: scroll`
ImageLoader: Larger image
MediaModal: Larger close button
MediaModal: Close the modal by swiping vertically
MediaModal: Show/hide close button and right/left navigation on tapping image
MediaModal: Change the `pointer-event` CSS prpp to get more blank space to close the modal
ImageLoader: Zoom/reset zoom on double tap
MediaModal: disable vertical swiping while horizontally swiped
ImageLoader: prevent propagating touchmove event to MediaModal
MediaModal: Adjust size and potision of buttons
ImageLoader: Adjust scroll potision on pinch zoom

* Remove "swipe to close" and "double tap to zoom" features

* remove unused prop and functions

removed `onScroll` prop and `handleScroll` func in ImageLoader

* separate zoom functionary to ZoomableImage component

adjust styling of ImageLoader
add styling for ZoomableImage

* adjust size and potision of close button of media modal

* Fix for gif video

add `onClick` prop to ExtendedVideoPlayer
specify `onClick` prop to video tag for switching nav of `MediaModal`
add `.video-modal` class to scss to separate styling for `VideoModal`

* fix styling for centering

specify height of `ZoomableImage` by pixel
clean styling for `ImageLoader`

* fix lint errors

* small fix

* fixed designated parts

6 files changed, 330 insertions, 93 deletions

diff --git a/app/javascript/mastodon/components/extended_video_player.js b/app/javascript/mastodon/components/extended_video_player.js
index f8bd067e8..9e2f6835a 100644
--- a/app/javascript/mastodon/components/extended_video_player.js
+++ b/app/javascript/mastodon/components/extended_video_player.js
@@ -11,6 +11,7 @@ export default class ExtendedVideoPlayer extends React.PureComponent {
     time: PropTypes.number,
     controls: PropTypes.bool.isRequired,
     muted: PropTypes.bool.isRequired,
+    onClick: PropTypes.func,
   };
 
   handleLoadedData = () => {
@@ -31,6 +32,12 @@ export default class ExtendedVideoPlayer extends React.PureComponent {
     this.video = c;
   }
 
+  handleClick = e => {
+    e.stopPropagation();
+    const handler = this.props.onClick;
+    if (handler) handler();
+  }
+
   render () {
     const { src, muted, controls, alt } = this.props;
 
@@ -46,6 +53,7 @@ export default class ExtendedVideoPlayer extends React.PureComponent {
           muted={muted}
           controls={controls}
           loop={!controls}
+          onClick={this.handleClick}
         />
       </div>
     );
diff --git a/app/javascript/mastodon/features/ui/components/image_loader.js b/app/javascript/mastodon/features/ui/components/image_loader.js
index e3e7197c5..c7360a726 100644
--- a/app/javascript/mastodon/features/ui/components/image_loader.js
+++ b/app/javascript/mastodon/features/ui/components/image_loader.js
@@ -1,6 +1,7 @@
 import React from 'react';
 import PropTypes from 'prop-types';
 import classNames from 'classnames';
+import ZoomableImage from './zoomable_image';
 
 export default class ImageLoader extends React.PureComponent {
 
@@ -10,6 +11,7 @@ export default class ImageLoader extends React.PureComponent {
     previewSrc: PropTypes.string,
     width: PropTypes.number,
     height: PropTypes.number,
+    onClick: PropTypes.func,
   }
 
   static defaultProps = {
@@ -24,6 +26,7 @@ export default class ImageLoader extends React.PureComponent {
   }
 
   removers = [];
+  canvas = null;
 
   get canvasContext() {
     if (!this.canvas) {
@@ -43,6 +46,10 @@ export default class ImageLoader extends React.PureComponent {
     }
   }
 
+  componentWillUnmount () {
+    this.removeEventListeners();
+  }
+
   loadImage (props) {
     this.removeEventListeners();
     this.setState({ loading: true, error: false });
@@ -118,7 +125,7 @@ export default class ImageLoader extends React.PureComponent {
   }
 
   render () {
-    const { alt, src, width, height } = this.props;
+    const { alt, src, width, height, onClick } = this.props;
     const { loading } = this.state;
 
     const className = classNames('image-loader', {
@@ -128,22 +135,19 @@ export default class ImageLoader extends React.PureComponent {
 
     return (
       <div className={className}>
-        <canvas
-          className='image-loader__preview-canvas'
-          width={width}
-          height={height}
-          ref={this.setCanvasRef}
-          style={{ opacity: loading ? 1 : 0 }}
-        />
-
-        {!loading && (
-          <img
-            alt={alt}
-            className='image-loader__img'
-            src={src}
+        {loading ? (
+          <canvas
+            className='image-loader__preview-canvas'
+            ref={this.setCanvasRef}
             width={width}
             height={height}
           />
+        ) : (
+          <ZoomableImage
+            alt={alt}
+            src={src}
+            onClick={onClick}
+          />
         )}
       </div>
     );
diff --git a/app/javascript/mastodon/features/ui/components/media_modal.js b/app/javascript/mastodon/features/ui/components/media_modal.js
index 02591a51f..72ef32256 100644
--- a/app/javascript/mastodon/features/ui/components/media_modal.js
+++ b/app/javascript/mastodon/features/ui/components/media_modal.js
@@ -3,6 +3,7 @@ import ReactSwipeableViews from 'react-swipeable-views';
 import ImmutablePropTypes from 'react-immutable-proptypes';
 import PropTypes from 'prop-types';
 import ExtendedVideoPlayer from '../../../components/extended_video_player';
+import classNames from 'classnames';
 import { defineMessages, injectIntl } from 'react-intl';
 import IconButton from '../../../components/icon_button';
 import ImmutablePureComponent from 'react-immutable-pure-component';
@@ -26,6 +27,7 @@ export default class MediaModal extends ImmutablePureComponent {
 
   state = {
     index: null,
+    navigationHidden: false,
   };
 
   handleSwipe = (index) => {
@@ -68,14 +70,21 @@ export default class MediaModal extends ImmutablePureComponent {
     return this.state.index !== null ? this.state.index : this.props.index;
   }
 
+  toggleNavigation = () => {
+    this.setState(prevState => ({
+      navigationHidden: !prevState.navigationHidden,
+    }));
+  };
+
   render () {
     const { media, intl, onClose } = this.props;
+    const { navigationHidden } = this.state;
 
     const index = this.getIndex();
     let pagination = [];
 
-    const leftNav  = media.size > 1 && <button tabIndex='0' className='modal-container__nav modal-container__nav--left' onClick={this.handlePrevClick} aria-label={intl.formatMessage(messages.previous)}><i className='fa fa-fw fa-chevron-left' /></button>;
-    const rightNav = media.size > 1 && <button tabIndex='0' className='modal-container__nav  modal-container__nav--right' onClick={this.handleNextClick} aria-label={intl.formatMessage(messages.next)}><i className='fa fa-fw fa-chevron-right' /></button>;
+    const leftNav  = media.size > 1 && <button tabIndex='0' className='media-modal__nav media-modal__nav--left' onClick={this.handlePrevClick} aria-label={intl.formatMessage(messages.previous)}><i className='fa fa-fw fa-chevron-left' /></button>;
+    const rightNav = media.size > 1 && <button tabIndex='0' className='media-modal__nav  media-modal__nav--right' onClick={this.handleNextClick} aria-label={intl.formatMessage(messages.next)}><i className='fa fa-fw fa-chevron-right' /></button>;
 
     if (media.size > 1) {
       pagination = media.map((item, i) => {
@@ -92,9 +101,30 @@ export default class MediaModal extends ImmutablePureComponent {
       const height = image.getIn(['meta', 'original', 'height']) || null;
 
       if (image.get('type') === 'image') {
-        return <ImageLoader previewSrc={image.get('preview_url')} src={image.get('url')} width={width} height={height} alt={image.get('description')} key={image.get('url')} />;
+        return (
+          <ImageLoader
+            previewSrc={image.get('preview_url')}
+            src={image.get('url')}
+            width={width}
+            height={height}
+            alt={image.get('description')}
+            key={image.get('url')}
+            onClick={this.toggleNavigation}
+          />
+        );
       } else if (image.get('type') === 'gifv') {
-        return <ExtendedVideoPlayer src={image.get('url')} muted controls={false} width={width} height={height} key={image.get('preview_url')} alt={image.get('description')} />;
+        return (
+          <ExtendedVideoPlayer
+            src={image.get('url')}
+            muted
+            controls={false}
+            width={width}
+            height={height}
+            key={image.get('preview_url')}
+            alt={image.get('description')}
+            onClick={this.toggleNavigation}
+          />
+        );
       }
 
       return null;
@@ -104,21 +134,43 @@ export default class MediaModal extends ImmutablePureComponent {
       alignItems: 'center', // center vertically
     };
 
+    const navigationClassName = classNames('media-modal__navigation', {
+      'media-modal__navigation--hidden': navigationHidden,
+    });
+
     return (
       <div className='modal-root__modal media-modal'>
-        {leftNav}
-
-        <div className='media-modal__content'>
-          <IconButton className='media-modal__close' title={intl.formatMessage(messages.close)} icon='times' onClick={onClose} size={16} />
-          <ReactSwipeableViews containerStyle={containerStyle} onChangeIndex={this.handleSwipe} index={index}>
-            {content}
-          </ReactSwipeableViews>
+        <div
+          className='media-modal__closer'
+          role='presentation'
+          onClick={onClose}
+        >
+          <div className='media-modal__content'>
+            <ReactSwipeableViews
+              style={{
+                // you can't use 100vh, because the viewport height is taller
+                // than the visible part of the document in some mobile
+                // browsers when it's address bar is visible.
+                // https://developers.google.com/web/updates/2016/12/url-bar-resizing
+                height: `${document.body.clientHeight}px`,
+              }}
+              containerStyle={containerStyle}
+              onChangeIndex={this.handleSwipe}
+              onSwitching={this.handleSwitching}
+              index={index}
+            >
+              {content}
+            </ReactSwipeableViews>
+          </div>
+        </div>
+        <div className={navigationClassName}>
+          <IconButton className='media-modal__close' title={intl.formatMessage(messages.close)} icon='times' onClick={onClose} size={40} />
+          {leftNav}
+          {rightNav}
+          <ul className='media-modal__pagination'>
+            {pagination}
+          </ul>
         </div>
-        <ul className='media-modal__pagination'>
-          {pagination}
-        </ul>
-
-        {rightNav}
       </div>
     );
   }
diff --git a/app/javascript/mastodon/features/ui/components/video_modal.js b/app/javascript/mastodon/features/ui/components/video_modal.js
index 6a883759f..9ed4a43ad 100644
--- a/app/javascript/mastodon/features/ui/components/video_modal.js
+++ b/app/javascript/mastodon/features/ui/components/video_modal.js
@@ -16,7 +16,7 @@ export default class VideoModal extends ImmutablePureComponent {
     const { media, time, onClose } = this.props;
 
     return (
-      <div className='modal-root__modal media-modal'>
+      <div className='modal-root__modal video-modal'>
         <div>
           <Video
             preview={media.get('preview_url')}
diff --git a/app/javascript/mastodon/features/ui/components/zoomable_image.js b/app/javascript/mastodon/features/ui/components/zoomable_image.js
new file mode 100644
index 000000000..0a0a4d41a
--- /dev/null
+++ b/app/javascript/mastodon/features/ui/components/zoomable_image.js
@@ -0,0 +1,151 @@
+import React from 'react';
+import PropTypes from 'prop-types';
+
+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 clamp = (min, max, value) => Math.min(max, Math.max(min, value));
+
+export default class ZoomableImage extends React.PureComponent {
+
+  static propTypes = {
+    alt: PropTypes.string,
+    src: PropTypes.string.isRequired,
+    width: PropTypes.number,
+    height: PropTypes.number,
+    onClick: PropTypes.func,
+  }
+
+  static defaultProps = {
+    alt: '',
+    width: null,
+    height: null,
+  };
+
+  state = {
+    scale: MIN_SCALE,
+  }
+
+  removers = [];
+  container = null;
+  image = null;
+  lastTouchEndTime = 0;
+  lastDistance = 0;
+
+  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));
+  }
+
+  componentWillUnmount () {
+    this.removeEventListeners();
+  }
+
+  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
+    e.stopPropagation();
+    const handler = this.props.onClick;
+    if (handler) handler();
+  }
+
+  setContainerRef = c => {
+    this.container = c;
+  }
+
+  setImageRef = c => {
+    this.image = c;
+  }
+
+  render () {
+    const { alt, src } = this.props;
+    const { scale } = this.state;
+    const overflow = scale === 1 ? 'hidden' : 'scroll';
+
+    return (
+      <div
+        className='zoomable-image'
+        ref={this.setContainerRef}
+        style={{ overflow }}
+      >
+        <img
+          role='presentation'
+          ref={this.setImageRef}
+          alt={alt}
+          src={src}
+          style={{
+            transform: `scale(${scale})`,
+            transformOrigin: '0 0',
+          }}
+          onClick={this.handleClick}
+        />
+      </div>
+    );
+  }
+
+}
diff --git a/app/javascript/styles/mastodon/components.scss b/app/javascript/styles/mastodon/components.scss
index a0ff0953b..bc6123cc7 100644
--- a/app/javascript/styles/mastodon/components.scss
+++ b/app/javascript/styles/mastodon/components.scss
@@ -1433,36 +1433,29 @@
 
 .image-loader {
   position: relative;
+  width: 100%;
+  height: 100%;
 
   &.image-loader--loading {
+    display: flex;
+    align-content: center;
+
     .image-loader__preview-canvas {
       filter: blur(2px);
     }
   }
 
-  .image-loader__img {
-    position: absolute;
-    top: 0;
-    left: 0;
-    right: 0;
-    max-width: 100%;
-    max-height: 100%;
-    background-image: none;
+  &.image-loader--amorphous .image-loader__preview-canvas {
+    display: none;
   }
+}
 
-  &.image-loader--amorphous {
-    position: static;
-
-    .image-loader__preview-canvas {
-      display: none;
-    }
-
-    .image-loader__img {
-      position: static;
-      width: auto;
-      height: auto;
-    }
-  }
+.zoomable-image {
+  position: relative;
+  width: 100%;
+  height: 100%;
+  display: flex;
+  align-content: center;
 }
 
 .navigation-bar {
@@ -2799,29 +2792,6 @@ a.status-card {
   }
 }
 
-.modal-container__nav {
-  align-items: center;
-  background: rgba($base-overlay-background, 0.5);
-  box-sizing: border-box;
-  border: 0;
-  color: $primary-text-color;
-  cursor: pointer;
-  display: flex;
-  font-size: 24px;
-  height: 100%;
-  padding: 30px 15px;
-  position: absolute;
-  top: 0;
-}
-
-.modal-container__nav--left {
-  left: -61px;
-}
-
-.modal-container__nav--right {
-  right: -61px;
-}
-
 .account--follows-info {
   color: $primary-text-color;
   position: absolute;
@@ -3418,29 +3388,27 @@ a.status-card {
   z-index: 9999;
 }
 
+.video-modal {
+  max-width: 100vw;
+  max-height: 100vh;
+  position: relative;
+}
+
 .media-modal {
-  max-width: 80vw;
-  max-height: 80vh;
+  width: 100%;
+  height: 100%;
   position: relative;
 
-  .extended-video-player,
   img,
   canvas,
   video {
-    max-width: 80vw;
-    max-height: 80vh;
+    max-width: 100vw;
+    max-height: 100vh;
     width: auto;
     height: auto;
     margin: auto;
   }
 
-  .extended-video-player,
-  video {
-    display: flex;
-    width: 80vw;
-    height: 80vh;
-  }
-
   img,
   canvas {
     display: block;
@@ -3449,12 +3417,65 @@ a.status-card {
   }
 
   .react-swipeable-view-container {
-    max-width: 80vw;
+    width: 100vw;
+    height: 100%;
   }
 }
 
-.media-modal__content {
-  background: $base-overlay-background;
+.media-modal__closer {
+  position: absolute;
+  top: 0;
+  left: 0;
+  right: 0;
+  bottom: 0;
+}
+
+.media-modal__navigation {
+  position: absolute;
+  top: 0;
+  left: 0;
+  right: 0;
+  bottom: 0;
+  pointer-events: none;
+  transition: opacity 0.3s linear;
+  will-change: opacity;
+
+  * {
+    pointer-events: auto;
+  }
+
+  &.media-modal__navigation--hidden {
+    opacity: 0;
+
+    * {
+      pointer-events: none;
+    }
+  }
+}
+
+.media-modal__nav {
+  background: rgba($base-overlay-background, 0.5);
+  box-sizing: border-box;
+  border: 0;
+  color: $primary-text-color;
+  cursor: pointer;
+  display: flex;
+  align-items: center;
+  font-size: 24px;
+  height: 20vmax;
+  margin: auto 0;
+  padding: 30px 15px;
+  position: absolute;
+  top: 0;
+  bottom: 0;
+}
+
+.media-modal__nav--left {
+  left: 0;
+}
+
+.media-modal__nav--right {
+  right: 0;
 }
 
 .media-modal__pagination {
@@ -3462,7 +3483,8 @@ a.status-card {
   text-align: center;
   position: absolute;
   left: 0;
-  bottom: -40px;
+  bottom: 20px;
+  pointer-events: none;
 }
 
 .media-modal__page-dot {
@@ -3486,8 +3508,8 @@ a.status-card {
 
 .media-modal__close {
   position: absolute;
-  right: 4px;
-  top: 4px;
+  right: 8px;
+  top: 8px;
   z-index: 100;
 }