Polish the screen shot example.

- Remove unneeded member variables.
- Set window sizes depending on screen geometry for High DPI screens.
- Flesh out code for saving the image, setting the supported
  mime types on the file dialog.
- Streamline constructor code, remove create...() functions.
- Use new connection syntax in createActions(),
- Obtain the screen from the widget.
- Adapt documentation. Remove note saying that widgets do not need
  the parent parameter (since creating parentless widgets can
  result in flicker in some cases), explain that QScreen pointers
  should be checked.

Change-Id: I0332bbf10eafe861fe3fd5573522694ab5c0183a
Reviewed-by: Topi Reiniö <topi.reinio@digia.com>

3 files changed, 71 insertions, 82 deletions

diff --git a/examples/widgets/desktop/screenshot/main.cpp b/examples/widgets/desktop/screenshot/main.cpp
index 788ebb3532..811562858a 100644
--- a/examples/widgets/desktop/screenshot/main.cpp
+++ b/examples/widgets/desktop/screenshot/main.cpp
@@ -39,13 +39,16 @@
 ****************************************************************************/
 
 #include <QApplication>
+#include <QDesktopWidget>
 
 #include "screenshot.h"
 
 int main(int argc, char *argv[])
 {
     QApplication app(argc, argv);
+
     Screenshot screenshot;
+    screenshot.move(QApplication::desktop()->availableGeometry(&screenshot).topLeft() + QPoint(20, 20));
     screenshot.show();
     return app.exec();
 }
diff --git a/examples/widgets/desktop/screenshot/screenshot.cpp b/examples/widgets/desktop/screenshot/screenshot.cpp
index bfca5a45ae..354fe36369 100644
--- a/examples/widgets/desktop/screenshot/screenshot.cpp
+++ b/examples/widgets/desktop/screenshot/screenshot.cpp
@@ -44,20 +44,48 @@
 
 //! [0]
 Screenshot::Screenshot()
+    :  screenshotLabel(new QLabel(this))
 {
-    screenshotLabel = new QLabel;
     screenshotLabel->setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
     screenshotLabel->setAlignment(Qt::AlignCenter);
-    screenshotLabel->setMinimumSize(240, 160);
 
-    createOptionsGroupBox();
-    createButtonsLayout();
+    const QRect screenGeometry = QApplication::desktop()->screenGeometry(this);
+    screenshotLabel->setMinimumSize(screenGeometry.width() / 8, screenGeometry.height() / 8);
 
-    mainLayout = new QVBoxLayout;
+    QVBoxLayout *mainLayout = new QVBoxLayout(this);
     mainLayout->addWidget(screenshotLabel);
+
+    QGroupBox *optionsGroupBox = new QGroupBox(tr("Options"), this);
+    delaySpinBox = new QSpinBox(optionsGroupBox);
+    delaySpinBox->setSuffix(tr(" s"));
+    delaySpinBox->setMaximum(60);
+
+    typedef void (QSpinBox::*QSpinBoxIntSignal)(int);
+    connect(delaySpinBox, static_cast<QSpinBoxIntSignal>(&QSpinBox::valueChanged),
+            this, &Screenshot::updateCheckBox);
+
+    hideThisWindowCheckBox = new QCheckBox(tr("Hide This Window"), optionsGroupBox);
+
+    QGridLayout *optionsGroupBoxLayout = new QGridLayout(optionsGroupBox);
+    optionsGroupBoxLayout->addWidget(new QLabel(tr("Screenshot Delay:"), this), 0, 0);
+    optionsGroupBoxLayout->addWidget(delaySpinBox, 0, 1);
+    optionsGroupBoxLayout->addWidget(hideThisWindowCheckBox, 1, 0, 1, 2);
+
     mainLayout->addWidget(optionsGroupBox);
+
+    QHBoxLayout *buttonsLayout = new QHBoxLayout;
+    newScreenshotButton = new QPushButton(tr("New Screenshot"), this);
+    connect(newScreenshotButton, &QPushButton::clicked, this, &Screenshot::newScreenshot);
+    buttonsLayout->addWidget(newScreenshotButton);
+    QPushButton *saveScreenshotButton = new QPushButton(tr("Save Screenshot"), this);
+    connect(saveScreenshotButton, &QPushButton::clicked, this, &Screenshot::saveScreenshot);
+    buttonsLayout->addWidget(saveScreenshotButton);
+    QPushButton *quitScreenshotButton = new QPushButton(tr("Quit"), this);
+    quitScreenshotButton->setShortcut(Qt::CTRL + Qt::Key_Q);
+    connect(quitScreenshotButton, &QPushButton::clicked, this, &QWidget::close);
+    buttonsLayout->addWidget(quitScreenshotButton);
+    buttonsLayout->addStretch();
     mainLayout->addLayout(buttonsLayout);
-    setLayout(mainLayout);
 
     shootScreen();
     delaySpinBox->setValue(5);
@@ -84,44 +112,59 @@ void Screenshot::newScreenshot()
         hide();
     newScreenshotButton->setDisabled(true);
 
-    QTimer::singleShot(delaySpinBox->value() * 1000, this, SLOT(shootScreen()));
+    QTimer::singleShot(delaySpinBox->value() * 1000, this, &Screenshot::shootScreen);
 }
 //! [2]
 
 //! [3]
 void Screenshot::saveScreenshot()
 {
-    QString format = "png";
-    QString initialPath = QDir::currentPath() + tr("/untitled.") + format;
-
-    QString fileName = QFileDialog::getSaveFileName(this, tr("Save As"), initialPath,
-                                                    tr("%1 Files (*.%2);;All Files (*)")
-                                                    .arg(format.toUpper())
-                                                    .arg(format));
-    if (!fileName.isEmpty())
-        originalPixmap.save(fileName, format.toLatin1().constData());
+    const QString format = "png";
+    QString initialPath = QStandardPaths::writableLocation(QStandardPaths::PicturesLocation);
+    if (initialPath.isEmpty())
+        initialPath = QDir::currentPath();
+    initialPath += tr("/untitled.") + format;
+
+    QFileDialog fileDialog(this, tr("Save As"), initialPath);
+    fileDialog.setAcceptMode(QFileDialog::AcceptSave);
+    fileDialog.setFileMode(QFileDialog::AnyFile);
+    fileDialog.setDirectory(initialPath);
+    QStringList mimeTypes;
+    foreach (const QByteArray &bf, QImageWriter::supportedMimeTypes())
+        mimeTypes.append(QLatin1String(bf));
+    fileDialog.setMimeTypeFilters(mimeTypes);
+    fileDialog.selectMimeTypeFilter("image/" + format);
+    fileDialog.setDefaultSuffix(format);
+    if (fileDialog.exec() != QDialog::Accepted)
+        return;
+    const QString fileName = fileDialog.selectedFiles().first();
+    if (!originalPixmap.save(fileName)) {
+        QMessageBox::warning(this, tr("Save Error"), tr("The image could not be saved to \"%1\".")
+                             .arg(QDir::toNativeSeparators(fileName)));
+    }
 }
 //! [3]
 
 //! [4]
 void Screenshot::shootScreen()
 {
-    if (delaySpinBox->value() != 0)
-        qApp->beep();
-//! [4]
-    originalPixmap = QPixmap(); // clear image for low memory situations
-                                // on embedded devices.
-//! [5]
     QScreen *screen = QGuiApplication::primaryScreen();
-    if (screen)
-        originalPixmap = screen->grabWindow(0);
+    if (const QWindow *window = windowHandle())
+        screen = window->screen();
+    if (!screen)
+        return;
+
+    if (delaySpinBox->value() != 0)
+        QApplication::beep();
+
+    originalPixmap = screen->grabWindow(0);
     updateScreenshotLabel();
 
     newScreenshotButton->setDisabled(false);
     if (hideThisWindowCheckBox->isChecked())
         show();
 }
-//! [5]
+//! [4]
 
 //! [6]
 void Screenshot::updateCheckBox()
@@ -135,52 +178,6 @@ void Screenshot::updateCheckBox()
 }
 //! [6]
 
-//! [7]
-void Screenshot::createOptionsGroupBox()
-{
-    optionsGroupBox = new QGroupBox(tr("Options"));
-
-    delaySpinBox = new QSpinBox;
-    delaySpinBox->setSuffix(tr(" s"));
-    delaySpinBox->setMaximum(60);
-    connect(delaySpinBox, SIGNAL(valueChanged(int)), this, SLOT(updateCheckBox()));
-
-    delaySpinBoxLabel = new QLabel(tr("Screenshot Delay:"));
-
-    hideThisWindowCheckBox = new QCheckBox(tr("Hide This Window"));
-
-    optionsGroupBoxLayout = new QGridLayout;
-    optionsGroupBoxLayout->addWidget(delaySpinBoxLabel, 0, 0);
-    optionsGroupBoxLayout->addWidget(delaySpinBox, 0, 1);
-    optionsGroupBoxLayout->addWidget(hideThisWindowCheckBox, 1, 0, 1, 2);
-    optionsGroupBox->setLayout(optionsGroupBoxLayout);
-}
-//! [7]
-
-//! [8]
-void Screenshot::createButtonsLayout()
-{
-    newScreenshotButton = createButton(tr("New Screenshot"), this, SLOT(newScreenshot()));
-    saveScreenshotButton = createButton(tr("Save Screenshot"), this, SLOT(saveScreenshot()));
-    quitScreenshotButton = createButton(tr("Quit"), this, SLOT(close()));
-
-    buttonsLayout = new QHBoxLayout;
-    buttonsLayout->addStretch();
-    buttonsLayout->addWidget(newScreenshotButton);
-    buttonsLayout->addWidget(saveScreenshotButton);
-    buttonsLayout->addWidget(quitScreenshotButton);
-}
-//! [8]
-
-//! [9]
-QPushButton *Screenshot::createButton(const QString &text, QWidget *receiver,
-                                      const char *member)
-{
-    QPushButton *button = new QPushButton(text);
-    button->connect(button, SIGNAL(clicked()), receiver, member);
-    return button;
-}
-//! [9]
 
 //! [10]
 void Screenshot::updateScreenshotLabel()
diff --git a/examples/widgets/desktop/screenshot/screenshot.h b/examples/widgets/desktop/screenshot/screenshot.h
index 352806cdba..f0e737e4c7 100644
--- a/examples/widgets/desktop/screenshot/screenshot.h
+++ b/examples/widgets/desktop/screenshot/screenshot.h
@@ -73,25 +73,14 @@ private slots:
     void updateCheckBox();
 
 private:
-    void createOptionsGroupBox();
-    void createButtonsLayout();
-    QPushButton *createButton(const QString &text, QWidget *receiver, const char *member);
     void updateScreenshotLabel();
 
     QPixmap originalPixmap;
 
     QLabel *screenshotLabel;
-    QGroupBox *optionsGroupBox;
     QSpinBox *delaySpinBox;
-    QLabel *delaySpinBoxLabel;
     QCheckBox *hideThisWindowCheckBox;
     QPushButton *newScreenshotButton;
-    QPushButton *saveScreenshotButton;
-    QPushButton *quitScreenshotButton;
-
-    QVBoxLayout *mainLayout;
-    QGridLayout *optionsGroupBoxLayout;
-    QHBoxLayout *buttonsLayout;
 };
 //! [0]