Added DockWidget::isInMainWindow()

For task #69.
A signal would be nice too, though.

src/DockWidgetBase.cpp

@@ -77,6 +77,20 @@ public:
         return qobject_cast<FloatingWindow*>(q->window());
     }
 
+    MainWindowBase *mainWindow() const
+    {
+        // Note: Don't simply use window(), as the MainWindow might be embedded into something else
+        QObject *p = q->parent();
+        while (p) {
+            if (auto window = qobject_cast<MainWindowBase*>(p))
+                return window;
+
+            p = p->parent();
+        }
+
+        return nullptr;
+    }
+
     QPoint defaultCenterPosForFloating();
 
     void updateTitle();
@@ -430,6 +444,11 @@ bool DockWidgetBase::isMainWindow() const
     return qobject_cast<MainWindowBase*>(widget());
 }
 
+bool DockWidgetBase::isInMainWindow() const
+{
+    return d->mainWindow() != nullptr;
+}
+
 bool DockWidgetBase::isFocused() const
 {
     auto f = this->frame();

src/DockWidgetBase.h

@@ -320,6 +320,16 @@ public:
      */
     bool isMainWindow() const;
 
+
+    /**
+     * @brief Returns whether this dock widget is docked into a main window.
+     *
+     * Note that isFloating() returning false might either mean the dock widget is docked into a
+     * main window or into a floating window (groupped/nested with other dock widgets. Use this function
+     * then if you need to disambiguate
+     */
+    bool isInMainWindow() const;
+
     ///@brief Returns whether This or any child of this dock widget is focused
     ///Not to be confused with QWidget::hasFocus(), which just refers to 1 widget. This includes
     ///variant includes children.

tests/tst_docks.cpp

@@ -429,6 +429,7 @@ private Q_SLOTS:
     void tst_stuckSeparator();
     void tst_isFocused();
     void tst_setWidget();
+    void tst_isInMainWindow();
 
 private:
     std::unique_ptr<MultiSplitter> createMultiSplitterFromSetup(MultiSplitterSetup setup, QHash<QWidget *, Frame *> &frameMap) const;
@@ -5822,6 +5823,19 @@ void TestDocks::tst_setWidget()
     delete dw;
 }
 
+void TestDocks::tst_isInMainWindow()
+{
+    EnsureTopLevelsDeleted e;
+    auto dw = new DockWidget(QStringLiteral("FOO"));
+    dw->show();
+    auto fw = dw->window();
+    QVERIFY(!dw->isInMainWindow());
+    auto m1 = createMainWindow(QSize(2560, 809), MainWindowOption_None, "MainWindow1");
+    m1->addDockWidget(dw, KDDockWidgets::Location_OnLeft);
+    QVERIFY(dw->isInMainWindow());
+    delete fw;
+}
+
 int main(int argc, char *argv[])
 {
     if (!qpaPassedAsArgument(argc, argv)) {