Vertical Tabs: Add child tab with middle click on "New Tab" button

Summary:
BUG: 393656

Reviewers: #falkon, drosca

Reviewed By: #falkon, drosca

Subscribers: drosca, falkon

Tags: #falkon

Differential Revision: https://phabricator.kde.org/D21664

src/plugins/VerticalTabs/verticaltabswidget.cpp

@@ -59,6 +59,7 @@ VerticalTabsWidget::VerticalTabsWidget(BrowserWindow *window)
     buttonAddTab->setIcon(QIcon::fromTheme(QSL("list-add")));
     buttonAddTab->setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Preferred);
     connect(buttonAddTab, &QAbstractButton::clicked, m_window, &BrowserWindow::addTab);
+    connect(buttonAddTab, &ToolButton::middleMouseClicked, this, &VerticalTabsWidget::addChildTab);
 
     m_groupMenu = new QMenu(this);
     buttonAddTab->setMenu(m_groupMenu);
@@ -201,3 +202,10 @@ void VerticalTabsWidget::updateGroupMenu()
         m_window->tabWidget()->addView(QUrl(QSL("extension://verticaltabs/group")), Qz::NT_SelectedTab);
     });
 }
+
+void VerticalTabsWidget::addChildTab()
+{
+    WebTab *tab = m_window->tabWidget()->webTab();
+    m_window->addTab();
+    m_window->tabWidget()->webTab()->setParentTab(tab);
+}

src/plugins/VerticalTabs/verticaltabswidget.h

@@ -43,6 +43,8 @@ public:
     void switchToNextTab();
     void switchToPreviousTab();
 
+    void addChildTab();
+
 private:
     WebTab *nextTab() const;
     WebTab *previousTab() const;