hellogl2 example: Streamline code

- Shorten menu code, add keyboard shortcuts and a quit action.
- Avoid calls to setLayout().
- Pass a parent to message boxes.
- Use the current screen for size calculation and consider
  availableGeometry().
- Prevent closing by the Escape key in docked mode.
- Split the dockUndock() function into dock()/undock() for clarity

Change-Id: I007da3bff86ee3f2dc8f87379e5d2ba2f0f6f3d7
Reviewed-by: Laszlo Agocs <laszlo.agocs@qt.io>
(cherry picked from commit 6f8398c8eb5476a6e98126d5b63421896b874271)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
(cherry picked from commit 734db610c3db3f00775d518b63d94695a2654389)

examples/opengl/hellogl2/mainwindow.cpp

@@ -3,19 +3,19 @@
 
 #include "mainwindow.h"
 #include "window.h"
+#include <QApplication>
+#include <QKeySequence>
 #include <QMenuBar>
 #include <QMenu>
 #include <QMessageBox>
 
 MainWindow::MainWindow()
 {
-    QMenuBar *menuBar = new QMenuBar;
-    QMenu *menuWindow = menuBar->addMenu(tr("&Window"));
-    QAction *addNew = new QAction(menuWindow);
-    addNew->setText(tr("Add new"));
-    menuWindow->addAction(addNew);
-    connect(addNew, &QAction::triggered, this, &MainWindow::onAddNew);
-    setMenuBar(menuBar);
+    QMenu *menuWindow = menuBar()->addMenu(tr("&Window"));
+    menuWindow->addAction(tr("Add new"), QKeySequence(Qt::CTRL | Qt::Key_N),
+                          this, &MainWindow::onAddNew);
+    menuWindow->addAction(tr("Quit"), QKeySequence(Qt::CTRL | Qt::Key_Q),
+                          qApp, QApplication::closeAllWindows);
 
     onAddNew();
 }
@@ -25,6 +25,6 @@ void MainWindow::onAddNew()
     if (!centralWidget())
         setCentralWidget(new Window(this));
     else
-        QMessageBox::information(nullptr, tr("Cannot add new window"),
+        QMessageBox::information(this, tr("Cannot Add New Window"),
                                  tr("Already occupied. Undock first."));
 }

examples/opengl/hellogl2/window.cpp

@@ -28,22 +28,19 @@ Window::Window(MainWindow *mw)
     connect(zSlider, &QSlider::valueChanged, glWidget, &GLWidget::setZRotation);
     connect(glWidget, &GLWidget::zRotationChanged, zSlider, &QSlider::setValue);
 
-    QVBoxLayout *mainLayout = new QVBoxLayout;
-    QHBoxLayout *container = new QHBoxLayout;
+    QVBoxLayout *mainLayout = new QVBoxLayout(this);
+    QWidget *w = new QWidget;
+    QHBoxLayout *container = new QHBoxLayout(w);
     container->addWidget(glWidget);
     container->addWidget(xSlider);
     container->addWidget(ySlider);
     container->addWidget(zSlider);
 
-    QWidget *w = new QWidget;
-    w->setLayout(container);
     mainLayout->addWidget(w);
     dockBtn = new QPushButton(tr("Undock"), this);
     connect(dockBtn, &QPushButton::clicked, this, &Window::dockUndock);
     mainLayout->addWidget(dockBtn);
 
-    setLayout(mainLayout);
-
     xSlider->setValue(15 * 16);
     ySlider->setValue(345 * 16);
     zSlider->setValue(0 * 16);
@@ -64,7 +61,7 @@ QSlider *Window::createSlider()
 
 void Window::keyPressEvent(QKeyEvent *e)
 {
-    if (e->key() == Qt::Key_Escape)
+    if (isWindow() && e->key() == Qt::Key_Escape)
         close();
     else
         QWidget::keyPressEvent(e);
@@ -72,26 +69,36 @@ void Window::keyPressEvent(QKeyEvent *e)
 
 void Window::dockUndock()
 {
-    if (parent()) {
-        setParent(nullptr);
-        setAttribute(Qt::WA_DeleteOnClose);
-        move(QGuiApplication::primaryScreen()->size().width() / 2 - width() / 2,
-             QGuiApplication::primaryScreen()->size().height() / 2 - height() / 2);
-        dockBtn->setText(tr("Dock"));
-        show();
-    } else {
-        if (!mainWindow->centralWidget()) {
-            if (mainWindow->isVisible()) {
-                setAttribute(Qt::WA_DeleteOnClose, false);
-                dockBtn->setText(tr("Undock"));
-                mainWindow->setCentralWidget(this);
-            } else {
-                QMessageBox::information(nullptr, tr("Cannot dock"),
-                                         tr("Main window already closed"));
-            }
-        } else {
-            QMessageBox::information(nullptr, tr("Cannot dock"),
-                                     tr("Main window already occupied"));
-        }
-    }
+    if (parent())
+        undock();
+    else
+        dock();
+}
+
+void Window::dock()
+{
+    if (!mainWindow->isVisible()) {
+        QMessageBox::information(this, tr("Cannot Dock"),
+                                 tr("Main window already closed"));
+        return;
+    }
+    if (mainWindow->centralWidget()) {
+        QMessageBox::information(this, tr("Cannot Dock"),
+                                 tr("Main window already occupied"));
+        return;
+    }
+    setAttribute(Qt::WA_DeleteOnClose, false);
+    dockBtn->setText(tr("Undock"));
+    mainWindow->setCentralWidget(this);
+}
+
+void Window::undock()
+{
+    setParent(nullptr);
+    setAttribute(Qt::WA_DeleteOnClose);
+    const auto geometry = screen()->availableGeometry();
+    move(geometry.x() + (geometry.width() - width()) / 2,
+         geometry.y() + (geometry.height() - height()) / 2);
+    dockBtn->setText(tr("Dock"));
+    show();
 }

examples/opengl/hellogl2/window.h

@@ -26,6 +26,8 @@ private slots:
     void dockUndock();
 
 private:
+    void dock();
+    void undock();
     QSlider *createSlider();
 
     GLWidget *glWidget;