Convert to state

js/src/forum/components/PostStreamScrubber.js

@@ -1,4 +1,5 @@
 import Component from '../../common/Component';
+import Button from '../../common/components/Button';
 import icon from '../../common/helpers/icon';
 import formatNumber from '../../common/utils/formatNumber';
 import ScrollListener from '../../common/utils/ScrollListener';
@@ -19,6 +20,8 @@ export default class PostStreamScrubber extends Component {
     this.stream = this.attrs.stream;
     this.handlers = {};
 
+    this.pendingMoveIndex = null;
+
     this.scrollListener = new ScrollListener(this.updateScrubberValues.bind(this, { fromScroll: true, forceHeightChange: true }));
   }
 
@@ -32,9 +35,9 @@ export default class PostStreamScrubber extends Component {
     });
 
     const index = this.stream.index;
+    const previousIndex = this.stream.previousIndex;
 
-    const showBackButton =
-      this.lastPosition > count / 20 && this.lastPosition < count - count / 20 && 100 * Math.abs((index - this.lastPosition) / count) > 25;
+    const showBackButton = previousIndex > count / 20 && previousIndex < count - count / 20 && 100 * Math.abs((index - previousIndex) / count) > 25;
 
     const unreadCount = this.stream.discussion.unreadCount();
     const unreadPercent = count ? Math.min(count - index, unreadCount) / count : 0;
@@ -57,6 +60,8 @@ export default class PostStreamScrubber extends Component {
     const classNames = ['PostStreamScrubber', 'Dropdown'];
     if (this.attrs.className) classNames.push(this.attrs.className);
 
+    console.log(showBackButton);
+
     return (
       <div className={classNames.join(' ')}>
         <button className="Button Dropdown-toggle" data-toggle="dropdown">
@@ -70,7 +75,11 @@ export default class PostStreamScrubber extends Component {
             </a>
 
             <div className="Scrubber-scrollbar">
-              {showBackButton ? this.backButton() : ''}
+              {showBackButton ? (
+                <a style={'top: ' + this.percentPerPost().index * this.stream.previousIndex + '%'} className="Scrubber-back" onclick={this.returnToLastPosition.bind(this)} title={app.translator.trans('core.forum.post_scrubber.back_title')}>
+                  {icon('fas fa-chevron-left')}
+                </a>
+              ) : ''}
               <div className="Scrubber-before" />
               <div className="Scrubber-handle">
                 <div className="Scrubber-bar" />
@@ -95,22 +104,11 @@ export default class PostStreamScrubber extends Component {
     );
   }
 
-  backButton() {
-    return (
-      <div style={'top: ' + this.percentPerPost().index * this.lastPosition + '%'} className="Scrubber-back">
-        {icon('fas fa-minus')}
-        <button className="Button Button--primary" onclick={this.returnToLastPosition.bind(this)}>
-          {app.translator.trans('core.forum.post_scrubber.back')}
-        </button>
-      </div>
-    );
-  }
-
   returnToLastPosition(e) {
     // Don't fire the scrubber click event as well
     e.stopPropagation();
 
-    this.stream.goToIndex(Math.floor(this.lastPosition));
+    this.stream.goToIndex(Math.floor(this.stream.previousIndex));
     this.updateScrubberValues({ animate: true });
 
     this.$().removeClass('open');
@@ -184,7 +182,7 @@ export default class PostStreamScrubber extends Component {
    * @param {Boolean} animate
    */
   updateScrubberValues(options = {}) {
-    const index = this.stream.index;
+    const index = this.pendingMoveIndex || this.stream.index;
     const count = this.stream.count();
     const visible = this.stream.visible || 1;
     const percentPerPost = this.percentPerPost();
@@ -226,7 +224,6 @@ export default class PostStreamScrubber extends Component {
    * Go to the first post in the discussion.
    */
   goToFirst() {
-    this.lastPosition = this.stream.index;
     this.stream.goToFirst();
     this.updateScrubberValues({ animate: true, forceHeightChange: true });
   }
@@ -235,7 +232,6 @@ export default class PostStreamScrubber extends Component {
    * Go to the last post in the discussion.
    */
   goToLast() {
-    this.lastPosition = this.stream.index;
     this.stream.goToLast();
     this.updateScrubberValues({ animate: true, forceHeightChange: true });
   }
@@ -261,7 +257,6 @@ export default class PostStreamScrubber extends Component {
     this.mouseStart = e.clientY || e.originalEvent.touches[0].clientY;
     this.indexStart = this.stream.index;
     this.dragging = true;
-    this.lastPosition = this.stream.index;
     $('body').css('cursor', 'move');
     this.$().toggleClass('dragging', this.dragging);
   }
@@ -278,7 +273,7 @@ export default class PostStreamScrubber extends Component {
     const deltaIndex = deltaPercent / this.percentPerPost().index || 0;
     const newIndex = Math.min(this.indexStart + deltaIndex, this.stream.count() - 1);
 
-    this.stream.index = Math.max(0, newIndex);
+    this.pendingMoveIndex = Math.max(0, newIndex);
     this.updateScrubberValues();
   }
 
@@ -295,8 +290,9 @@ export default class PostStreamScrubber extends Component {
 
     // If the index we've landed on is in a gap, then tell the stream-
     // content that we want to load those posts.
-    const intIndex = Math.floor(this.stream.index);
+    const intIndex = Math.floor(this.pendingMoveIndex);
     this.stream.goToIndex(intIndex);
+    this.pendingMoveIndex = null;
   }
 
   onclick(e) {
@@ -308,7 +304,6 @@ export default class PostStreamScrubber extends Component {
     const $scrollbar = this.$('.Scrubber-scrollbar');
     const offsetPixels = (e.pageY || e.originalEvent.touches[0].pageY) - $scrollbar.offset().top + $('body').scrollTop();
     let offsetPercent = (offsetPixels / $scrollbar.outerHeight()) * 100;
-    this.lastPosition = this.stream.index;
 
     // 2. We want the handle of the scrollbar to end up centered on the click
     //    position. Thus, we calculate the height of the handle in percent and

js/src/forum/states/PostStreamState.js

@@ -22,6 +22,7 @@ class PostStreamState {
     this.pagesLoading = 0;
 
     this.index = 0;
+    this.previousIndex = 0;
     this.number = 1;
 
     /**
@@ -137,6 +138,7 @@ class PostStreamState {
     this.needsScroll = true;
     this.targetPost = { index };
     this.animateScroll = !noAnimation;
+    this.previousIndex = (index === this.previousIndex) ? index : this.index;
     this.index = index;
 
     m.redraw();

less/forum/Scrubber.less

@@ -24,21 +24,10 @@
 }
 .Scrubber-back {
   position: absolute;
+  left: 12.5px;
   z-index: 1;
-
-  .icon {
-    margin-left: -0.35em;
   color: @muted-color;
 }
-
-  .Button {
-    padding: 5px;
-    position: absolute;
-    left: 15px;
-    top: -5px;
-    width: initial;
-  }
-}
 .Scrubber-unread {
   position: absolute;
   border-left: 1px solid lighten(@muted-color, 10%);