use ResizeNotifier as well to relayout room list

src/components/structures/LeftPanel.js

@@ -234,7 +234,7 @@ const LeftPanel = React.createClass({
                     <CallPreview ConferenceHandler={VectorConferenceHandler} />
                     <RoomList
                         ref={this.collectRoomList}
-                        toolbarShown={this.props.toolbarShown}
+                        resizeNotifier={this.props.resizeNotifier}
                         collapsed={this.props.collapsed}
                         searchFilter={this.state.searchFilter}
                         ConferenceHandler={VectorConferenceHandler} />

src/components/structures/LoggedInView.js

@@ -543,7 +543,7 @@ const LoggedInView = React.createClass({
                 <DragDropContext onDragEnd={this._onDragEnd}>
                     <div ref={this._setResizeContainerRef} className={bodyClasses}>
                         <LeftPanel
-                            toolbarShown={!!topBar}
+                            resizeNotifier={this.props.resizeNotifier}
                             collapsed={this.props.collapseLhs || false}
                             disabled={this.props.leftDisabled}
                         />

src/components/views/rooms/RoomList.js

@@ -212,7 +212,7 @@ module.exports = React.createClass({
         this._checkSubListsOverflow();
 
         this.resizer.attach();
-        window.addEventListener("resize", this.onWindowResize);
+        this.props.resizeNotifier.on("leftPanelResized", this.onResize);
         this.mounted = true;
     },
 
@@ -260,7 +260,6 @@ module.exports = React.createClass({
     componentWillUnmount: function() {
         this.mounted = false;
 
-        window.removeEventListener("resize", this.onWindowResize);
         dis.unregister(this.dispatcherRef);
         if (MatrixClientPeg.get()) {
             MatrixClientPeg.get().removeListener("Room", this.onRoom);
@@ -272,6 +271,8 @@ module.exports = React.createClass({
             MatrixClientPeg.get().removeListener("Group.myMembership", this._onGroupMyMembership);
             MatrixClientPeg.get().removeListener("RoomState.events", this.onRoomStateEvents);
         }
+        this.props.resizeNotifier.removeListener("leftPanelResized", this.onResize);
+
 
         if (this._tagStoreToken) {
             this._tagStoreToken.remove();
@@ -293,13 +294,14 @@ module.exports = React.createClass({
         this._delayedRefreshRoomList.cancelPendingCall();
     },
 
-    onWindowResize: function() {
+
+    onResize: function() {
         if (this.mounted && this._layout && this.resizeContainer &&
             Array.isArray(this._layoutSections)
         ) {
             this._layout.update(
                 this._layoutSections,
-                this.resizeContainer.offsetHeight
+                this.resizeContainer.offsetHeight,
             );
         }
     },

src/utils/ResizeNotifier.js

@@ -31,11 +31,13 @@ export default class ResizeNotifier extends EventEmitter {
     }
 
     notifyBannersChanged() {
+        this.emit("leftPanelResized");
         this.emit("middlePanelResized");
     }
 
     // can be called in quick succession
     notifyLeftHandleResized() {
+        // don't emit event for own region
         this._throttledMiddlePanel();
     }
 
@@ -46,6 +48,12 @@ export default class ResizeNotifier extends EventEmitter {
 
     // can be called in quick succession
     notifyWindowResized() {
+        // no need to throttle this one,
+        // also it could make scrollbars appear for
+        // a split second when the room list manual layout is now
+        // taller than the available space
+        this.emit("leftPanelResized");
+
         this._throttledMiddlePanel();
     }
 }