screenshot.cpp Example File

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 #include <QtWidgets>

 #include "screenshot.h"

 Screenshot::Screenshot()
     :  screenshotLabel(new QLabel(this))
 {
     screenshotLabel->setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
     screenshotLabel->setAlignment(Qt::AlignCenter);

     const QRect screenGeometry = QApplication::desktop()->screenGeometry(this);
     screenshotLabel->setMinimumSize(screenGeometry.width() / 8, screenGeometry.height() / 8);

     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);

     connect(delaySpinBox, QOverload<int>::of(&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);

     shootScreen();
     delaySpinBox->setValue(5);

     setWindowTitle(tr("Screenshot"));
     resize(300, 200);
 }

 void Screenshot::resizeEvent(QResizeEvent * /* event */)
 {
     QSize scaledSize = originalPixmap.size();
     scaledSize.scale(screenshotLabel->size(), Qt::KeepAspectRatio);
     if (!screenshotLabel->pixmap() || scaledSize != screenshotLabel->pixmap()->size())
         updateScreenshotLabel();
 }

 void Screenshot::newScreenshot()
 {
     if (hideThisWindowCheckBox->isChecked())
         hide();
     newScreenshotButton->setDisabled(true);

     QTimer::singleShot(delaySpinBox->value() * 1000, this, &Screenshot::shootScreen);
 }

 void Screenshot::saveScreenshot()
 {
     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)));
     }
 }

 void Screenshot::shootScreen()
 {
     QScreen *screen = QGuiApplication::primaryScreen();
     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();
 }

 void Screenshot::updateCheckBox()
 {
     if (delaySpinBox->value() == 0) {
         hideThisWindowCheckBox->setDisabled(true);
         hideThisWindowCheckBox->setChecked(false);
     } else {
         hideThisWindowCheckBox->setDisabled(false);
     }
 }

 void Screenshot::updateScreenshotLabel()
 {
     screenshotLabel->setPixmap(originalPixmap.scaled(screenshotLabel->size(),
                                                      Qt::KeepAspectRatio,
                                                      Qt::SmoothTransformation));
 }