examples: Show how to hide dock indicators when ctrl is pressed

Fixes issue #334 and issue #337.
Won't add this directly into the library, as each project
has different requirements regarding this.

It's easy to do in application code though.

(cherry picked from commit af455bb)

examples/dockwidgets/MyMainWindow.cpp

@@ -21,6 +21,7 @@
 #include <QDebug>
 #include <QString>
 #include <QTextEdit>
+#include <QWindow>
 #include <QRandomGenerator>
 
 #include <QApplication>
@@ -123,6 +124,9 @@ MyMainWindow::MyMainWindow(const QString &uniqueName, KDDockWidgets::MainWindowO
     if (options & KDDockWidgets::MainWindowOption_HasCentralWidget) {
         setPersistentCentralWidget(new MyWidget1());
     }
+
+    // optional, just for demo purposes regarding pressing Ctrl key to hide drop indicators
+    qApp->installEventFilter(this);
 }
 
 MyMainWindow::~MyMainWindow()
@@ -215,3 +219,26 @@ KDDockWidgets::Views::DockWidget_qtwidgets *MyMainWindow::newDockWidget()
     count++;
     return dock;
 }
+
+bool MyMainWindow::eventFilter(QObject *obj, QEvent *ev)
+{
+    // This event filter is just for examplify how to use the KDDW API to hide
+    // the drag indicators when ctrl is pressed
+
+    switch (ev->type()) {
+    case QEvent::KeyPress:
+    case QEvent::KeyRelease: {
+        auto kev = static_cast<QKeyEvent *>(ev);
+        if (kev->key() == Qt::Key_Control && qobject_cast<QWindow *>(obj)) {
+            const bool hideIndicators = ev->type() == QEvent::KeyPress;
+            KDDockWidgets::Config::self().setDropIndicatorsInhibited(hideIndicators);
+        }
+    }
+
+    break;
+    default:
+        break;
+    }
+
+    return false;
+}

examples/dockwidgets/MyMainWindow.h

@@ -29,6 +29,7 @@ class MyMainWindow : public KDDockWidgets::Views::MainWindow_qtwidgets
 
 private:
     void createDockWidgets();
+    bool eventFilter(QObject *obj, QEvent *ev) override;
     KDDockWidgets::Views::DockWidget_qtwidgets *newDockWidget();
     QMenu *m_toggleMenu = nullptr;
     const bool m_dockWidget0IsNonClosable;