More mobile UX improvements

- Reposition the composer when shown
- Make preview button scroll the parent frame down
- Fix iframe infinite height loop

extensions/embed/js/forum/src/main.js

@@ -1,6 +1,7 @@
 import { override, extend } from 'flarum/extend';
 import app from 'flarum/app';
 import Composer from 'flarum/components/Composer';
+import PostStream from 'flarum/components/PostStream';
 import ModalManager from 'flarum/components/ModalManager';
 import AlertManager from 'flarum/components/AlertManager';
 import PostMeta from 'flarum/components/PostMeta';
@@ -37,10 +38,13 @@ app.initializers.replace('boot', () => {
 
   app.pageInfo = m.prop();
 
-  extend(ModalManager.prototype, 'show', function() {
+  const reposition = function() {
     const info = app.pageInfo();
     this.$().css('top', Math.max(0, info.scrollTop - info.offsetTop));
-  });
+  };
+
+  extend(ModalManager.prototype, 'show', reposition);
+  extend(Composer.prototype, 'show', reposition);
 
   window.iFrameResizer = {
     readyCallback: function() {
@@ -48,6 +52,13 @@ app.initializers.replace('boot', () => {
     }
   };
 
+  extend(PostStream.prototype, 'goToNumber', function(promise, number) {
+    if (number === 'reply' && 'parentIFrame' in window && app.composer.$().css('position') === 'absolute') {
+      const itemTop = this.$('.PostStream-item:last').offset().top;
+      window.parentIFrame.scrollToOffset(0, itemTop);
+    }
+  });
+
   app.pane = new Pane(document.getElementById('app'));
   app.drawer = new Drawer();
   app.composer = m.mount(document.getElementById('composer'), Composer.component());

extensions/embed/less/forum/extension.less

@@ -9,6 +9,7 @@
 .App {
   padding-top: 0;
   min-height: 0;
+  overflow: hidden;
 
   &:before {
     display: none;
@@ -16,6 +17,7 @@
 }
 .App-content {
   border-top: 0;
+  min-height: 0;
 }
 .DiscussionPage-nav--embed {
   @media @tablet-up {
@@ -80,4 +82,7 @@
       right: 0 !important;
     }
   }
+  .Composer:not(.minimized) {
+    height: 400px !important;
+  }
 }