Fix chat window scrolling to stay at bottom

Stay at bottom window when:
- There is new chat.
- People come and go from online list.
- Chat window hides and restores when application focus changes.
- Interface is minimized and restored.

interface/src/ui/ChatWindow.cpp

@@ -248,6 +248,7 @@ void ChatWindow::notificationClicked() {
             return;
         }
     }
+    Application::processEvents();
 
     scrollToBottom();
 }
@@ -262,6 +263,8 @@ void ChatWindow::error(QXmppClient::Error error) {
 }
 
 void ChatWindow::participantsChanged() {
+    bool atBottom = isNearBottom();
+
     QStringList participants = XmppClient::getInstance().getPublicChatRoom()->participants();
     ui->numOnlineLabel->setText(tr("%1 online now:").arg(participants.count()));
 
@@ -288,6 +291,11 @@ void ChatWindow::participantsChanged() {
         userLabel->installEventFilter(this);
         ui->usersWidget->layout()->addWidget(userLabel);
     }
+    Application::processEvents();
+
+    if (atBottom) {
+        scrollToBottom();
+    }
 }
 
 void ChatWindow::messageReceived(const QXmppMessage& message) {