Tabs: Allow to detach tab from window with only one tab

Window will be closed after detaching this tab.

src/lib/tabwidget/tabbar.cpp

@@ -484,7 +484,7 @@ void TabBar::mouseMoveEvent(QMouseEvent* event)
         } else if (eventY > height()) {
             offset = eventY - height();
         }
-        if (count() > 1 && offset > QApplication::startDragDistance()) {
+        if (offset > QApplication::startDragDistance()) {
             const QPoint global = mapToGlobal(m_dragStartPosition);
             QWidget *w = QApplication::widgetAt(global);
             if (w) {

src/lib/tabwidget/tabwidget.cpp

@@ -655,16 +655,15 @@ void TabWidget::detachTab(WebTab* tab)
     disconnect(tab->webView(), SIGNAL(ipChanged(QString)), m_window->ipLabel(), SLOT(setText(QString)));
 
     tab->detach();
+
+    if (count() == 0) {
+        m_window->close();
+    }
 }
 
 void TabWidget::detachTab(int index)
 {
     WebTab* tab = weTab(index);
-
-    if (count() <= 1) {
-        return;
-    }
-
     detachTab(tab);
     tab->setPinned(false);
 

src/lib/webtab/webtab.cpp

@@ -1,6 +1,6 @@
 /* ============================================================
 * Falkon - Qt web browser
-* Copyright (C) 2010-2017 David Rosca <nowrep@gmail.com>
+* Copyright (C) 2010-2018 David Rosca <nowrep@gmail.com>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
@@ -274,7 +274,8 @@ void WebTab::detach()
     Q_ASSERT(m_tabBar);
 
     // Remove icon from tab
-    m_tabBar->setTabButton(tabIndex(), m_tabBar->iconButtonPosition(), 0);
+    m_tabBar->setTabButton(tabIndex(), m_tabBar->iconButtonPosition(), nullptr);
+    m_tabIcon->setParent(this);
 
     // Remove the tab from tabbar
     setParent(0);