Add a "load more" button to the end of the post stream

This is necessary if the page is viewed in a context with no scrolling, i.e. an auto-resizing iframe

js/forum/src/components/PostStream.js

@@ -5,6 +5,7 @@ import anchorScroll from 'flarum/utils/anchorScroll';
 import mixin from 'flarum/utils/mixin';
 import evented from 'flarum/utils/evented';
 import ReplyPlaceholder from 'flarum/components/ReplyPlaceholder';
+import Button from 'flarum/components/Button';
 
 /**
  * The `PostStream` component displays an infinitely-scrollable wall of posts in
@@ -194,11 +195,10 @@ class PostStream extends Component {
     this.visibleEnd = this.sanitizeIndex(this.visibleEnd);
     this.viewingEnd = this.visibleEnd === this.count();
 
+    const posts = this.posts();
     const postIds = this.discussion.postIds();
 
-    return (
-      <div className="PostStream">
-        {this.posts().map((post, i) => {
+    const items = posts.map((post, i) => {
       let content;
       const attrs = {'data-index': this.visibleStart + i};
 
@@ -235,19 +235,31 @@ class PostStream extends Component {
       }
 
       return <div className="PostStream-item" {...attrs}>{content}</div>;
-        })}
+    });
+
+    if (!this.viewingEnd && posts[this.visibleEnd - this.visibleStart - 1]) {
+      items.push(
+        <div className="PostStream-loadMore" key="loadMore">
+          <Button className="Button" onclick={this.loadNext.bind(this)}>
+            {app.translator.trans('core.forum.post_stream.load_more_button')}
+          </Button>
+        </div>
+      );
+    }
 
-        {
     // If we're viewing the end of the discussion, the user can reply, and
     // is not already doing so, then show a 'write a reply' placeholder.
-          this.viewingEnd &&
-            (!app.session.user || this.discussion.canReply())
-            ? (
+    if (this.viewingEnd && (!app.session.user || this.discussion.canReply())) {
+      items.push(
         <div className="PostStream-item" key="reply">
           {ReplyPlaceholder.component({discussion: this.discussion})}
         </div>
-            ) : ''
+      );
     }
+
+    return (
+      <div className="PostStream">
+        {items}
       </div>
     );
   }