Add ability to specify alternative text for media attachments (#5123)

* Fix #117 - Add ability to specify alternative text for media attachments

- POST /api/v1/media accepts `description` straight away
- PUT /api/v1/media/:id to update `description` (only for unattached ones)
- Serialized as `name` of Document object in ActivityPub
- Uploads form adjusted for better performance and description input

* Add tests

* Change undo button blend mode to difference

24 files changed, 311 insertions, 278 deletions

diff --git a/app/controllers/api/v1/media_controller.rb b/app/controllers/api/v1/media_controller.rb
index 8a1992fca..9f330f0df 100644
--- a/app/controllers/api/v1/media_controller.rb
+++ b/app/controllers/api/v1/media_controller.rb
@@ -10,7 +10,7 @@ class Api::V1::MediaController < Api::BaseController
   respond_to :json
 
   def create
-    @media = current_account.media_attachments.create!(file: media_params[:file])
+    @media = current_account.media_attachments.create!(media_params)
     render json: @media, serializer: REST::MediaAttachmentSerializer
   rescue Paperclip::Errors::NotIdentifiedByImageMagickError
     render json: file_type_error, status: 422
@@ -18,10 +18,16 @@ class Api::V1::MediaController < Api::BaseController
     render json: processing_error, status: 500
   end
 
+  def update
+    @media = current_account.media_attachments.where(status_id: nil).find(params[:id])
+    @media.update!(media_params)
+    render json: @media, serializer: REST::MediaAttachmentSerializer
+  end
+
   private
 
   def media_params
-    params.permit(:file)
+    params.permit(:file, :description)
   end
 
   def file_type_error
diff --git a/app/javascript/mastodon/actions/compose.js b/app/javascript/mastodon/actions/compose.js
index 9f10a8c15..8be5b939f 100644
--- a/app/javascript/mastodon/actions/compose.js
+++ b/app/javascript/mastodon/actions/compose.js
@@ -37,6 +37,10 @@ export const COMPOSE_COMPOSING_CHANGE = 'COMPOSE_COMPOSING_CHANGE';
 
 export const COMPOSE_EMOJI_INSERT = 'COMPOSE_EMOJI_INSERT';
 
+export const COMPOSE_UPLOAD_CHANGE_REQUEST     = 'COMPOSE_UPLOAD_UPDATE_REQUEST';
+export const COMPOSE_UPLOAD_CHANGE_SUCCESS     = 'COMPOSE_UPLOAD_UPDATE_SUCCESS';
+export const COMPOSE_UPLOAD_CHANGE_FAIL        = 'COMPOSE_UPLOAD_UPDATE_FAIL';
+
 export function changeCompose(text) {
   return {
     type: COMPOSE_CHANGE,
@@ -165,6 +169,40 @@ export function uploadCompose(files) {
   };
 };
 
+export function changeUploadCompose(id, description) {
+  return (dispatch, getState) => {
+    dispatch(changeUploadComposeRequest());
+
+    api(getState).put(`/api/v1/media/${id}`, { description }).then(response => {
+      dispatch(changeUploadComposeSuccess(response.data));
+    }).catch(error => {
+      dispatch(changeUploadComposeFail(id, error));
+    });
+  };
+};
+
+export function changeUploadComposeRequest() {
+  return {
+    type: COMPOSE_UPLOAD_CHANGE_REQUEST,
+    skipLoading: true,
+  };
+};
+export function changeUploadComposeSuccess(media) {
+  return {
+    type: COMPOSE_UPLOAD_CHANGE_SUCCESS,
+    media: media,
+    skipLoading: true,
+  };
+};
+
+export function changeUploadComposeFail(error) {
+  return {
+    type: COMPOSE_UPLOAD_CHANGE_FAIL,
+    error: error,
+    skipLoading: true,
+  };
+};
+
 export function uploadComposeRequest() {
   return {
     type: COMPOSE_UPLOAD_REQUEST,
diff --git a/app/javascript/mastodon/components/extended_video_player.js b/app/javascript/mastodon/components/extended_video_player.js
index 5ab5e9e58..f8bd067e8 100644
--- a/app/javascript/mastodon/components/extended_video_player.js
+++ b/app/javascript/mastodon/components/extended_video_player.js
@@ -5,6 +5,7 @@ export default class ExtendedVideoPlayer extends React.PureComponent {
 
   static propTypes = {
     src: PropTypes.string.isRequired,
+    alt: PropTypes.string,
     width: PropTypes.number,
     height: PropTypes.number,
     time: PropTypes.number,
@@ -31,15 +32,20 @@ export default class ExtendedVideoPlayer extends React.PureComponent {
   }
 
   render () {
+    const { src, muted, controls, alt } = this.props;
+
     return (
       <div className='extended-video-player'>
         <video
           ref={this.setRef}
-          src={this.props.src}
+          src={src}
           autoPlay
-          muted={this.props.muted}
-          controls={this.props.controls}
-          loop={!this.props.controls}
+          role='button'
+          tabIndex='0'
+          aria-label={alt}
+          muted={muted}
+          controls={controls}
+          loop={!controls}
         />
       </div>
     );
diff --git a/app/javascript/mastodon/components/media_gallery.js b/app/javascript/mastodon/components/media_gallery.js
index a81409871..38b26b1fc 100644
--- a/app/javascript/mastodon/components/media_gallery.js
+++ b/app/javascript/mastodon/components/media_gallery.js
@@ -136,7 +136,7 @@ class Item extends React.PureComponent {
           onClick={this.handleClick}
           target='_blank'
         >
-          <img src={previewUrl} srcSet={srcSet} sizes={sizes} alt='' />
+          <img src={previewUrl} srcSet={srcSet} sizes={sizes} alt={attachment.get('description')} />
         </a>
       );
     } else if (attachment.get('type') === 'gifv') {
@@ -146,6 +146,7 @@ class Item extends React.PureComponent {
         <div className={classNames('media-gallery__gifv', { autoplay: autoPlay })}>
           <video
             className='media-gallery__item-gifv-thumbnail'
+            aria-label={attachment.get('description')}
             role='application'
             src={attachment.get('url')}
             onClick={this.handleClick}
diff --git a/app/javascript/mastodon/components/video_player.js b/app/javascript/mastodon/components/video_player.js
deleted file mode 100644
index 2a2d91c33..000000000
--- a/app/javascript/mastodon/components/video_player.js
+++ /dev/null
@@ -1,204 +0,0 @@
-import React from 'react';
-import ImmutablePropTypes from 'react-immutable-proptypes';
-import PropTypes from 'prop-types';
-import IconButton from './icon_button';
-import { defineMessages, injectIntl, FormattedMessage } from 'react-intl';
-import { isIOS } from '../is_mobile';
-
-const messages = defineMessages({
-  toggle_sound: { id: 'video_player.toggle_sound', defaultMessage: 'Toggle sound' },
-  toggle_visible: { id: 'video_player.toggle_visible', defaultMessage: 'Toggle visibility' },
-  expand_video: { id: 'video_player.expand', defaultMessage: 'Expand video' },
-});
-
-@injectIntl
-export default class VideoPlayer extends React.PureComponent {
-
-  static contextTypes = {
-    router: PropTypes.object,
-  };
-
-  static propTypes = {
-    media: ImmutablePropTypes.map.isRequired,
-    width: PropTypes.number,
-    height: PropTypes.number,
-    sensitive: PropTypes.bool,
-    intl: PropTypes.object.isRequired,
-    autoplay: PropTypes.bool,
-    onOpenVideo: PropTypes.func.isRequired,
-  };
-
-  static defaultProps = {
-    width: 239,
-    height: 110,
-  };
-
-  state = {
-    visible: !this.props.sensitive,
-    preview: true,
-    muted: true,
-    hasAudio: true,
-    videoError: false,
-  };
-
-  handleClick = () => {
-    this.setState({ muted: !this.state.muted });
-  }
-
-  handleVideoClick = (e) => {
-    e.stopPropagation();
-
-    const node = this.video;
-
-    if (node.paused) {
-      node.play();
-    } else {
-      node.pause();
-    }
-  }
-
-  handleOpen = () => {
-    this.setState({ preview: !this.state.preview });
-  }
-
-  handleVisibility = () => {
-    this.setState({
-      visible: !this.state.visible,
-      preview: true,
-    });
-  }
-
-  handleExpand = () => {
-    this.video.pause();
-    this.props.onOpenVideo(this.props.media, this.video.currentTime);
-  }
-
-  setRef = (c) => {
-    this.video = c;
-  }
-
-  handleLoadedData = () => {
-    if (('WebkitAppearance' in document.documentElement.style && this.video.audioTracks.length === 0) || this.video.mozHasAudio === false) {
-      this.setState({ hasAudio: false });
-    }
-  }
-
-  handleVideoError = () => {
-    this.setState({ videoError: true });
-  }
-
-  componentDidMount () {
-    if (!this.video) {
-      return;
-    }
-
-    this.video.addEventListener('loadeddata', this.handleLoadedData);
-    this.video.addEventListener('error', this.handleVideoError);
-  }
-
-  componentDidUpdate () {
-    if (!this.video) {
-      return;
-    }
-
-    this.video.addEventListener('loadeddata', this.handleLoadedData);
-    this.video.addEventListener('error', this.handleVideoError);
-  }
-
-  componentWillUnmount () {
-    if (!this.video) {
-      return;
-    }
-
-    this.video.removeEventListener('loadeddata', this.handleLoadedData);
-    this.video.removeEventListener('error', this.handleVideoError);
-  }
-
-  render () {
-    const { media, intl, width, height, sensitive, autoplay } = this.props;
-
-    let spoilerButton = (
-      <div className={`status__video-player-spoiler ${this.state.visible ? 'status__video-player-spoiler--visible' : ''}`}>
-        <IconButton overlay title={intl.formatMessage(messages.toggle_visible)} icon={this.state.visible ? 'eye' : 'eye-slash'} onClick={this.handleVisibility} />
-      </div>
-    );
-
-    let expandButton = '';
-
-    if (this.context.router) {
-      expandButton = (
-        <div className='status__video-player-expand'>
-          <IconButton overlay title={intl.formatMessage(messages.expand_video)} icon='expand' onClick={this.handleExpand} />
-        </div>
-      );
-    }
-
-    let muteButton = '';
-
-    if (this.state.hasAudio) {
-      muteButton = (
-        <div className='status__video-player-mute'>
-          <IconButton overlay title={intl.formatMessage(messages.toggle_sound)} icon={this.state.muted ? 'volume-off' : 'volume-up'} onClick={this.handleClick} />
-        </div>
-      );
-    }
-
-    if (!this.state.visible) {
-      if (sensitive) {
-        return (
-          <button style={{ width: `${width}px`, height: `${height}px`, marginTop: '8px' }} className='media-spoiler' onClick={this.handleVisibility}>
-            {spoilerButton}
-            <span className='media-spoiler__warning'><FormattedMessage id='status.sensitive_warning' defaultMessage='Sensitive content' /></span>
-            <span className='media-spoiler__trigger'><FormattedMessage id='status.sensitive_toggle' defaultMessage='Click to view' /></span>
-          </button>
-        );
-      } else {
-        return (
-          <button style={{ width: `${width}px`, height: `${height}px`, marginTop: '8px' }} className='media-spoiler' onClick={this.handleVisibility}>
-            {spoilerButton}
-            <span className='media-spoiler__warning'><FormattedMessage id='status.media_hidden' defaultMessage='Media hidden' /></span>
-            <span className='media-spoiler__trigger'><FormattedMessage id='status.sensitive_toggle' defaultMessage='Click to view' /></span>
-          </button>
-        );
-      }
-    }
-
-    if (this.state.preview && !autoplay) {
-      return (
-        <button className='media-spoiler-video' style={{ width: `${width}px`, height: `${height}px`, backgroundImage: `url(${media.get('preview_url')})` }} onClick={this.handleOpen}>
-          {spoilerButton}
-          <div className='media-spoiler-video-play-icon'><i className='fa fa-play' /></div>
-        </button>
-      );
-    }
-
-    if (this.state.videoError) {
-      return (
-        <div style={{ width: `${width}px`, height: `${height}px` }} className='video-error-cover' >
-          <span className='media-spoiler__warning'><FormattedMessage id='video_player.video_error' defaultMessage='Video could not be played' /></span>
-        </div>
-      );
-    }
-
-    return (
-      <div className='status__video-player' style={{ width: `${width}px`, height: `${height}px` }}>
-        {spoilerButton}
-        {muteButton}
-        {expandButton}
-
-        <video
-          className='status__video-player-video'
-          role='button'
-          tabIndex='0'
-          ref={this.setRef}
-          src={media.get('url')}
-          autoPlay={!isIOS()}
-          loop
-          muted={this.state.muted}
-          onClick={this.handleVideoClick}
-        />
-      </div>
-    );
-  }
-
-}
diff --git a/app/javascript/mastodon/features/compose/components/upload.js b/app/javascript/mastodon/features/compose/components/upload.js
new file mode 100644
index 000000000..c2bf3b72e
--- /dev/null
+++ b/app/javascript/mastodon/features/compose/components/upload.js
@@ -0,0 +1,96 @@
+import React from 'react';
+import ImmutablePropTypes from 'react-immutable-proptypes';
+import PropTypes from 'prop-types';
+import IconButton from '../../../components/icon_button';
+import Motion from 'react-motion/lib/Motion';
+import spring from 'react-motion/lib/spring';
+import ImmutablePureComponent from 'react-immutable-pure-component';
+import { defineMessages, injectIntl } from 'react-intl';
+import classNames from 'classnames';
+
+const messages = defineMessages({
+  undo: { id: 'upload_form.undo', defaultMessage: 'Undo' },
+  description: { id: 'upload_form.description', defaultMessage: 'Describe for the visually impaired' },
+});
+
+@injectIntl
+export default class Upload extends ImmutablePureComponent {
+
+  static propTypes = {
+    media: ImmutablePropTypes.map.isRequired,
+    intl: PropTypes.object.isRequired,
+    onUndo: PropTypes.func.isRequired,
+    onDescriptionChange: PropTypes.func.isRequired,
+  };
+
+  state = {
+    hovered: false,
+    focused: false,
+    dirtyDescription: null,
+  };
+
+  handleUndoClick = () => {
+    this.props.onUndo(this.props.media.get('id'));
+  }
+
+  handleInputChange = e => {
+    this.setState({ dirtyDescription: e.target.value });
+  }
+
+  handleMouseEnter = () => {
+    this.setState({ hovered: true });
+  }
+
+  handleMouseLeave = () => {
+    this.setState({ hovered: false });
+  }
+
+  handleInputFocus = () => {
+    this.setState({ focused: true });
+  }
+
+  handleInputBlur = () => {
+    const { dirtyDescription } = this.state;
+
+    this.setState({ focused: false, dirtyDescription: null });
+
+    if (dirtyDescription !== null) {
+      this.props.onDescriptionChange(this.props.media.get('id'), dirtyDescription);
+    }
+  }
+
+  render () {
+    const { intl, media } = this.props;
+    const active          = this.state.hovered || this.state.focused;
+    const description     = this.state.dirtyDescription || media.get('description') || '';
+
+    return (
+      <div className='compose-form__upload' onMouseEnter={this.handleMouseEnter} onMouseLeave={this.handleMouseLeave}>
+        <Motion defaultStyle={{ scale: 0.8 }} style={{ scale: spring(1, { stiffness: 180, damping: 12 }) }}>
+          {({ scale }) => (
+            <div className='compose-form__upload-thumbnail' style={{ transform: `translateZ(0) scale(${scale})`, backgroundImage: `url(${media.get('preview_url')})` }}>
+              <IconButton icon='times' title={intl.formatMessage(messages.undo)} size={36} onClick={this.handleUndoClick} />
+
+              <div className={classNames('compose-form__upload-description', { active })}>
+                <label>
+                  <span style={{ display: 'none' }}>{intl.formatMessage(messages.description)}</span>
+
+                  <input
+                    placeholder={intl.formatMessage(messages.description)}
+                    type='text'
+                    value={description}
+                    maxLength={140}
+                    onFocus={this.handleInputFocus}
+                    onChange={this.handleInputChange}
+                    onBlur={this.handleInputBlur}
+                  />
+                </label>
+              </div>
+            </div>
+          )}
+        </Motion>
+      </div>
+    );
+  }
+
+}
diff --git a/app/javascript/mastodon/features/compose/components/upload_form.js b/app/javascript/mastodon/features/compose/components/upload_form.js
index cf2d2658a..b7f112205 100644
--- a/app/javascript/mastodon/features/compose/components/upload_form.js
+++ b/app/javascript/mastodon/features/compose/components/upload_form.js
@@ -1,49 +1,27 @@
 import React from 'react';
 import ImmutablePropTypes from 'react-immutable-proptypes';
-import PropTypes from 'prop-types';
-import IconButton from '../../../components/icon_button';
-import { defineMessages, injectIntl } from 'react-intl';
 import UploadProgressContainer from '../containers/upload_progress_container';
-import Motion from 'react-motion/lib/Motion';
-import spring from 'react-motion/lib/spring';
+import ImmutablePureComponent from 'react-immutable-pure-component';
+import UploadContainer from '../containers/upload_container';
 
-const messages = defineMessages({
-  undo: { id: 'upload_form.undo', defaultMessage: 'Undo' },
-});
-
-@injectIntl
-export default class UploadForm extends React.PureComponent {
+export default class UploadForm extends ImmutablePureComponent {
 
   static propTypes = {
-    media: ImmutablePropTypes.list.isRequired,
-    onRemoveFile: PropTypes.func.isRequired,
-    intl: PropTypes.object.isRequired,
+    mediaIds: ImmutablePropTypes.list.isRequired,
   };
 
-  onRemoveFile = (e) => {
-    const id = e.currentTarget.parentElement.getAttribute('data-id');
-    this.props.onRemoveFile(id);
-  }
-
   render () {
-    const { intl, media } = this.props;
-
-    const uploads = media.map(attachment =>
-      <div className='compose-form__upload' key={attachment.get('id')}>
-        <Motion defaultStyle={{ scale: 0.8 }} style={{ scale: spring(1, { stiffness: 180, damping: 12 }) }}>
-          {({ scale }) =>
-            <div className='compose-form__upload-thumbnail' data-id={attachment.get('id')} style={{ transform: `translateZ(0) scale(${scale})`, backgroundImage: `url(${attachment.get('preview_url')})` }}>
-              <IconButton icon='times' title={intl.formatMessage(messages.undo)} size={36} onClick={this.onRemoveFile} />
-            </div>
-          }
-        </Motion>
-      </div>
-    );
+    const { mediaIds } = this.props;
 
     return (
       <div className='compose-form__upload-wrapper'>
         <UploadProgressContainer />
-        <div className='compose-form__uploads-wrapper'>{uploads}</div>
+
+        <div className='compose-form__uploads-wrapper'>
+          {mediaIds.map(id => (
+            <UploadContainer id={id} key={id} />
+          ))}
+        </div>
       </div>
     );
   }
diff --git a/app/javascript/mastodon/features/compose/containers/upload_container.js b/app/javascript/mastodon/features/compose/containers/upload_container.js
new file mode 100644
index 000000000..ca9c3b704
--- /dev/null
+++ b/app/javascript/mastodon/features/compose/containers/upload_container.js
@@ -0,0 +1,21 @@
+import { connect } from 'react-redux';
+import Upload from '../components/upload';
+import { undoUploadCompose, changeUploadCompose } from '../../../actions/compose';
+
+const mapStateToProps = (state, { id }) => ({
+  media: state.getIn(['compose', 'media_attachments']).find(item => item.get('id') === id),
+});
+
+const mapDispatchToProps = dispatch => ({
+
+  onUndo: id => {
+    dispatch(undoUploadCompose(id));
+  },
+
+  onDescriptionChange: (id, description) => {
+    dispatch(changeUploadCompose(id, description));
+  },
+
+});
+
+export default connect(mapStateToProps, mapDispatchToProps)(Upload);
diff --git a/app/javascript/mastodon/features/compose/containers/upload_form_container.js b/app/javascript/mastodon/features/compose/containers/upload_form_container.js
index 4612599f1..a6798bf51 100644
--- a/app/javascript/mastodon/features/compose/containers/upload_form_container.js
+++ b/app/javascript/mastodon/features/compose/containers/upload_form_container.js
@@ -1,17 +1,8 @@
 import { connect } from 'react-redux';
 import UploadForm from '../components/upload_form';
-import { undoUploadCompose } from '../../../actions/compose';
 
 const mapStateToProps = state => ({
-  media: state.getIn(['compose', 'media_attachments']),
+  mediaIds: state.getIn(['compose', 'media_attachments']).map(item => item.get('id')),
 });
 
-const mapDispatchToProps = dispatch => ({
-
-  onRemoveFile (media_id) {
-    dispatch(undoUploadCompose(media_id));
-  },
-
-});
-
-export default connect(mapStateToProps, mapDispatchToProps)(UploadForm);
+export default connect(mapStateToProps)(UploadForm);
diff --git a/app/javascript/mastodon/features/ui/components/media_modal.js b/app/javascript/mastodon/features/ui/components/media_modal.js
index 828419d5a..da2ceecb1 100644
--- a/app/javascript/mastodon/features/ui/components/media_modal.js
+++ b/app/javascript/mastodon/features/ui/components/media_modal.js
@@ -76,9 +76,9 @@ 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} key={image.get('preview_url')} />;
+        return <ImageLoader previewSrc={image.get('preview_url')} src={image.get('url')} width={width} height={height} alt={image.get('description')} key={image.get('preview_url')} />;
       } else if (image.get('type') === 'gifv') {
-        return <ExtendedVideoPlayer src={image.get('url')} muted controls={false} width={width} height={height} key={image.get('preview_url')} />;
+        return <ExtendedVideoPlayer src={image.get('url')} muted controls={false} width={width} height={height} key={image.get('preview_url')} alt={image.get('description')} />;
       }
 
       return null;
@@ -90,6 +90,7 @@ export default class MediaModal extends ImmutablePureComponent {
 
         <div className='media-modal__content'>
           <IconButton className='media-modal__close' title={intl.formatMessage(messages.close)} icon='times' onClick={onClose} size={16} />
+
           <ReactSwipeableViews onChangeIndex={this.handleSwipe} index={index} animateHeight>
             {content}
           </ReactSwipeableViews>
diff --git a/app/javascript/mastodon/features/ui/components/video_modal.js b/app/javascript/mastodon/features/ui/components/video_modal.js
index 867c73ed5..1437deeb0 100644
--- a/app/javascript/mastodon/features/ui/components/video_modal.js
+++ b/app/javascript/mastodon/features/ui/components/video_modal.js
@@ -23,6 +23,7 @@ export default class VideoModal extends ImmutablePureComponent {
             src={media.get('url')}
             startTime={time}
             onCloseVideo={onClose}
+            description={media.get('description')}
           />
         </div>
       </div>
diff --git a/app/javascript/mastodon/features/ui/util/async-components.js b/app/javascript/mastodon/features/ui/util/async-components.js
index b8c5e885a..ad5493f8c 100644
--- a/app/javascript/mastodon/features/ui/util/async-components.js
+++ b/app/javascript/mastodon/features/ui/util/async-components.js
@@ -90,10 +90,6 @@ export function MediaGallery () {
   return import(/* webpackChunkName: "status/media_gallery" */'../../../components/media_gallery');
 }
 
-export function VideoPlayer () {
-  return import(/* webpackChunkName: "status/video_player" */'../../../components/video_player');
-}
-
 export function Video () {
   return import(/* webpackChunkName: "features/video" */'../../video');
 }
diff --git a/app/javascript/mastodon/features/video/index.js b/app/javascript/mastodon/features/video/index.js
index f228e434b..069264ef5 100644
--- a/app/javascript/mastodon/features/video/index.js
+++ b/app/javascript/mastodon/features/video/index.js
@@ -104,6 +104,7 @@ export default class Video extends React.PureComponent {
   static propTypes = {
     preview: PropTypes.string,
     src: PropTypes.string.isRequired,
+    alt: PropTypes.string,
     width: PropTypes.number,
     height: PropTypes.number,
     sensitive: PropTypes.bool,
@@ -247,7 +248,7 @@ export default class Video extends React.PureComponent {
   }
 
   render () {
-    const { preview, src, width, height, startTime, onOpenVideo, onCloseVideo, intl } = this.props;
+    const { preview, src, width, height, startTime, onOpenVideo, onCloseVideo, intl, alt } = this.props;
     const { progress, dragging, paused, fullscreen, hovered, muted, revealed } = this.state;
 
     return (
@@ -260,6 +261,7 @@ export default class Video extends React.PureComponent {
           loop
           role='button'
           tabIndex='0'
+          aria-label={alt}
           width={width}
           height={height}
           onClick={this.togglePlay}
diff --git a/app/javascript/mastodon/reducers/compose.js b/app/javascript/mastodon/reducers/compose.js
index 9d39584fc..082d4d370 100644
--- a/app/javascript/mastodon/reducers/compose.js
+++ b/app/javascript/mastodon/reducers/compose.js
@@ -22,6 +22,9 @@ import {
   COMPOSE_VISIBILITY_CHANGE,
   COMPOSE_COMPOSING_CHANGE,
   COMPOSE_EMOJI_INSERT,
+  COMPOSE_UPLOAD_CHANGE_REQUEST,
+  COMPOSE_UPLOAD_CHANGE_SUCCESS,
+  COMPOSE_UPLOAD_CHANGE_FAIL,
 } from '../actions/compose';
 import { TIMELINE_DELETE } from '../actions/timelines';
 import { STORE_HYDRATE } from '../actions/store';
@@ -220,15 +223,15 @@ export default function compose(state = initialState, action) {
       map.set('idempotencyKey', uuid());
     });
   case COMPOSE_SUBMIT_REQUEST:
+  case COMPOSE_UPLOAD_CHANGE_REQUEST:
     return state.set('is_submitting', true);
   case COMPOSE_SUBMIT_SUCCESS:
     return clearAll(state);
   case COMPOSE_SUBMIT_FAIL:
+  case COMPOSE_UPLOAD_CHANGE_FAIL:
     return state.set('is_submitting', false);
   case COMPOSE_UPLOAD_REQUEST:
-    return state.withMutations(map => {
-      map.set('is_uploading', true);
-    });
+    return state.set('is_uploading', true);
   case COMPOSE_UPLOAD_SUCCESS:
     return appendMedia(state, fromJS(action.media));
   case COMPOSE_UPLOAD_FAIL:
@@ -256,6 +259,16 @@ export default function compose(state = initialState, action) {
     }
   case COMPOSE_EMOJI_INSERT:
     return insertEmoji(state, action.position, action.emoji);
+  case COMPOSE_UPLOAD_CHANGE_SUCCESS:
+    return state
+      .set('is_submitting', false)
+      .update('media_attachments', list => list.map(item => {
+        if (item.get('id') === action.media.id) {
+          return item.set('description', action.media.description);
+        }
+
+        return item;
+      }));
   default:
     return state;
   }
diff --git a/app/javascript/styles/components.scss b/app/javascript/styles/components.scss
index da479347b..631cd7a13 100644
--- a/app/javascript/styles/components.scss
+++ b/app/javascript/styles/components.scss
@@ -335,12 +335,52 @@
 
 .compose-form__uploads-wrapper {
   display: flex;
+  flex-direction: row;
   padding: 5px;
+  flex-wrap: wrap;
 }
 
 .compose-form__upload {
   flex: 1 1 0;
+  min-width: 40%;
   margin: 5px;
+
+  &-description {
+    position: absolute;
+    z-index: 2;
+    bottom: 0;
+    left: 0;
+    right: 0;
+    box-sizing: border-box;
+    background: linear-gradient(0deg, rgba($base-shadow-color, 0.8) 0, rgba($base-shadow-color, 0.35) 80%, transparent);
+    padding: 10px;
+    opacity: 0;
+    transition: opacity .1s ease;
+
+    input {
+      background: transparent;
+      color: $ui-secondary-color;
+      border: 0;
+      padding: 0;
+      margin: 0;
+      width: 100%;
+      font-family: inherit;
+      font-size: 14px;
+      font-weight: 500;
+
+      &:focus {
+        color: $white;
+      }
+    }
+
+    &.active {
+      opacity: 1;
+    }
+  }
+
+  .icon-button {
+    mix-blend-mode: difference;
+  }
 }
 
 .compose-form__upload-thumbnail {
@@ -352,13 +392,6 @@
   width: 100%;
 }
 
-.compose-form__upload-cancel {
-  background-size: cover;
-  border-radius: 4px;
-  height: 100px;
-  width: 100px;
-}
-
 .compose-form__label {
   display: block;
   line-height: 24px;
diff --git a/app/lib/activitypub/activity/create.rb b/app/lib/activitypub/activity/create.rb
index 4e19b3096..55addd66e 100644
--- a/app/lib/activitypub/activity/create.rb
+++ b/app/lib/activitypub/activity/create.rb
@@ -105,7 +105,7 @@ class ActivityPub::Activity::Create < ActivityPub::Activity
       next if unsupported_media_type?(attachment['mediaType']) || attachment['url'].blank?
 
       href             = Addressable::URI.parse(attachment['url']).normalize.to_s
-      media_attachment = MediaAttachment.create(status: status, account: status.account, remote_url: href)
+      media_attachment = MediaAttachment.create(status: status, account: status.account, remote_url: href, description: attachment['name'].presence)
 
       next if skip_download?
 
diff --git a/app/models/media_attachment.rb b/app/models/media_attachment.rb
index e4a974f96..25e41c209 100644
--- a/app/models/media_attachment.rb
+++ b/app/models/media_attachment.rb
@@ -16,6 +16,7 @@
 #  shortcode         :string
 #  type              :integer          default("image"), not null
 #  file_meta         :json
+#  description       :text
 #
 
 require 'mime/types'
@@ -58,6 +59,7 @@ class MediaAttachment < ApplicationRecord
   validates_attachment_size :file, less_than: 8.megabytes
 
   validates :account, presence: true
+  validates :description, length: { maximum: 140 }, if: :local?
 
   scope :attached,   -> { where.not(status_id: nil) }
   scope :unattached, -> { where(status_id: nil) }
@@ -78,6 +80,7 @@ class MediaAttachment < ApplicationRecord
     shortcode
   end
 
+  before_create :prepare_description, unless: :local?
   before_create :set_shortcode
   before_post_process :set_type_and_extension
   before_save :set_meta
@@ -136,6 +139,10 @@ class MediaAttachment < ApplicationRecord
     end
   end
 
+  def prepare_description
+    self.description = description.strip[0...140] unless description.nil?
+  end
+
   def set_type_and_extension
     self.type = VIDEO_MIME_TYPES.include?(file_content_type) ? :video : :image
     extension = appropriate_extension
diff --git a/app/serializers/activitypub/note_serializer.rb b/app/serializers/activitypub/note_serializer.rb
index f94c3b9dc..4dbf6a444 100644
--- a/app/serializers/activitypub/note_serializer.rb
+++ b/app/serializers/activitypub/note_serializer.rb
@@ -89,12 +89,16 @@ class ActivityPub::NoteSerializer < ActiveModel::Serializer
   class MediaAttachmentSerializer < ActiveModel::Serializer
     include RoutingHelper
 
-    attributes :type, :media_type, :url
+    attributes :type, :media_type, :url, :name
 
     def type
       'Document'
     end
 
+    def name
+      object.description
+    end
+
     def media_type
       object.file_content_type
     end
diff --git a/app/serializers/rest/media_attachment_serializer.rb b/app/serializers/rest/media_attachment_serializer.rb
index f6e7c79d1..e6e9c8e82 100644
--- a/app/serializers/rest/media_attachment_serializer.rb
+++ b/app/serializers/rest/media_attachment_serializer.rb
@@ -4,7 +4,8 @@ class REST::MediaAttachmentSerializer < ActiveModel::Serializer
   include RoutingHelper
 
   attributes :id, :type, :url, :preview_url,
-             :remote_url, :text_url, :meta
+             :remote_url, :text_url, :meta,
+             :description
 
   def id
     object.id.to_s
diff --git a/config/routes.rb b/config/routes.rb
index cb7e84d7b..ad2d8fca2 100644
--- a/config/routes.rb
+++ b/config/routes.rb
@@ -193,7 +193,7 @@ Rails.application.routes.draw do
       get '/search', to: 'search#index', as: :search
 
       resources :follows,    only: [:create]
-      resources :media,      only: [:create]
+      resources :media,      only: [:create, :update]
       resources :apps,       only: [:create]
       resources :blocks,     only: [:index]
       resources :mutes,      only: [:index]
diff --git a/db/migrate/20170927215609_add_description_to_media_attachments.rb b/db/migrate/20170927215609_add_description_to_media_attachments.rb
new file mode 100644
index 000000000..db8d76566
--- /dev/null
+++ b/db/migrate/20170927215609_add_description_to_media_attachments.rb
@@ -0,0 +1,5 @@
+class AddDescriptionToMediaAttachments < ActiveRecord::Migration[5.1]
+  def change
+    add_column :media_attachments, :description, :text
+  end
+end
diff --git a/db/schema.rb b/db/schema.rb
index e16599d32..90f8a5683 100644
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 20170924022025) do
+ActiveRecord::Schema.define(version: 20170927215609) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -161,6 +161,7 @@ ActiveRecord::Schema.define(version: 20170924022025) do
     t.string "shortcode"
     t.integer "type", default: 0, null: false
     t.json "file_meta"
+    t.text "description"
     t.index ["account_id"], name: "index_media_attachments_on_account_id"
     t.index ["shortcode"], name: "index_media_attachments_on_shortcode", unique: true
     t.index ["status_id"], name: "index_media_attachments_on_status_id"
diff --git a/spec/controllers/api/v1/media_controller_spec.rb b/spec/controllers/api/v1/media_controller_spec.rb
index baa22d7e4..0e494638f 100644
--- a/spec/controllers/api/v1/media_controller_spec.rb
+++ b/spec/controllers/api/v1/media_controller_spec.rb
@@ -101,4 +101,33 @@ RSpec.describe Api::V1::MediaController, type: :controller do
       end
     end
   end
+
+  describe 'PUT #update' do
+    context 'when somebody else\'s' do
+      let(:media) { Fabricate(:media_attachment, status: nil) }
+
+      it 'returns http not found' do
+        put :update, params: { id: media.id, description: 'Lorem ipsum!!!' }
+        expect(response).to have_http_status(:not_found)
+      end
+    end
+
+    context 'when not attached to a status' do
+      let(:media) { Fabricate(:media_attachment, status: nil, account: user.account) }
+
+      it 'updates the description' do
+        put :update, params: { id: media.id, description: 'Lorem ipsum!!!' }
+        expect(media.reload.description).to eq 'Lorem ipsum!!!'
+      end
+    end
+
+    context 'when attached to a status' do
+      let(:media) { Fabricate(:media_attachment, status: Fabricate(:status), account: user.account) }
+
+      it 'returns http not found' do
+        put :update, params: { id: media.id, description: 'Lorem ipsum!!!' }
+        expect(response).to have_http_status(:not_found)
+      end
+    end
+  end
 end
diff --git a/spec/models/media_attachment_spec.rb b/spec/models/media_attachment_spec.rb
index f6717b7d5..f20698c45 100644
--- a/spec/models/media_attachment_spec.rb
+++ b/spec/models/media_attachment_spec.rb
@@ -17,7 +17,6 @@ RSpec.describe MediaAttachment, type: :model do
       expect(media.file.meta["original"]["height"]).to eq 128
       expect(media.file.meta["original"]["aspect"]).to eq 1.0
     end
-
   end
 
   describe 'non-animated gif non-conversion' do
@@ -50,4 +49,12 @@ RSpec.describe MediaAttachment, type: :model do
       expect(media.file.meta["small"]["aspect"]).to eq 400.0/267
     end
   end
+
+  describe 'descriptions for remote attachments' do
+    it 'are cut off at 140 characters' do
+      media = Fabricate(:media_attachment, description: 'foo' * 100, remote_url: 'http://example.com/blah.jpg')
+
+      expect(media.description.size).to be <= 140
+    end
+  end
 end