exportdialog.cpp Example File

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 #include "exportdialog.h"

 #include <QApplication>
 #include <QDesktopWidget>
 #include <QDialogButtonBox>
 #include <QFileDialog>
 #include <QFormLayout>
 #include <QHBoxLayout>
 #include <QMessageBox>
 #include <QLabel>
 #include <QLineEdit>
 #include <QPushButton>
 #include <QSpinBox>
 #include <QToolButton>
 #include <QVBoxLayout>

 #include <QImageWriter>

 #include <QDebug>

 #include <QDir>
 #include <QFileInfo>

 enum { exportMinimumSize = 1, exportMaximumSize = 2000 };

 ExportDialog::ExportDialog(QWidget *parent)
     : QDialog(parent)
     , m_fileNameLineEdit(new QLineEdit(this))
     , m_widthSpinBox(new QSpinBox(this))
     , m_heightSpinBox(new QSpinBox(this))
     , m_aspectRatio(1)
 {
     typedef void (QSpinBox::*QSpinBoxIntSignal)(int);

     setWindowFlags(windowFlags() & ~Qt::WindowContextHelpButtonHint);
     setWindowTitle(tr("Export"));

     QFormLayout *formLayout = new QFormLayout(this);

     QHBoxLayout *fileLayout = new QHBoxLayout;
     fileLayout->addWidget(m_fileNameLineEdit);
     m_fileNameLineEdit->setMinimumWidth(QApplication::desktop()->availableGeometry(this).width() / 6);
     QPushButton *browseButton = new QPushButton(tr("Browse..."), this);
     fileLayout->addWidget(browseButton);
     connect(browseButton, &QAbstractButton::clicked, this, &ExportDialog::browse);
     formLayout->addRow(tr("File:"), fileLayout);

     QHBoxLayout *sizeLayout = new QHBoxLayout;
     sizeLayout->addStretch();
     m_widthSpinBox->setMinimum(exportMinimumSize);
     m_widthSpinBox->setMaximum(exportMaximumSize);
     connect(m_widthSpinBox, static_cast<QSpinBoxIntSignal>(&QSpinBox::valueChanged),
             this, &ExportDialog::exportWidthChanged);
     sizeLayout->addWidget(m_widthSpinBox);
     //: Multiplication, as in 32x32
     sizeLayout->addWidget(new QLabel(tr("x")));
     m_heightSpinBox->setMinimum(exportMinimumSize);
     m_heightSpinBox->setMaximum(exportMaximumSize);
     connect(m_heightSpinBox, static_cast<QSpinBoxIntSignal>(&QSpinBox::valueChanged),
             this, &ExportDialog::exportHeightChanged);
     sizeLayout->addWidget(m_heightSpinBox);
     QToolButton *resetButton = new QToolButton(this);
     resetButton->setIcon(QIcon(":/qt-project.org/styles/commonstyle/images/refresh-32.png"));
     sizeLayout->addWidget(resetButton);
     connect(resetButton, &QAbstractButton::clicked, this, &ExportDialog::resetExportSize);
     formLayout->addRow(tr("Size:"), sizeLayout);

     QDialogButtonBox *buttonBox = new QDialogButtonBox(QDialogButtonBox::Ok | QDialogButtonBox::Cancel, this);
     connect(buttonBox, &QDialogButtonBox::accepted, this, &QDialog::accept);
     connect(buttonBox, &QDialogButtonBox::rejected, this, &QDialog::reject);
     formLayout->addRow(buttonBox);
 }

 void ExportDialog::accept()
 {
     const QString fileName = exportFileName();
     if (fileName.isEmpty()) {
         QMessageBox::warning(this, windowTitle(), tr("Please enter a file name"));
         return;
     }
     QFileInfo fi(fileName);
     if (fi.exists()) {
         const QString question = tr("%1 already exists.\nWould you like to overwrite it?").arg(QDir::toNativeSeparators(fileName));
         if (QMessageBox::question(this, windowTitle(), question, QMessageBox::Yes | QMessageBox::No) !=  QMessageBox::Yes)
             return;
     }
     QDialog::accept();
 }

 QSize ExportDialog::exportSize() const
 {
     return QSize(m_widthSpinBox->value(), m_heightSpinBox->value());
 }

 void ExportDialog::setExportSize(const QSize &size)
 {
     m_defaultSize = size;
     QSizeF defaultSizeF(m_defaultSize);
     m_aspectRatio = defaultSizeF.width() / defaultSizeF.height();
     setExportWidthBlocked(size.width());
     setExportHeightBlocked(size.height());
 }

 void ExportDialog::resetExportSize()
 {
     setExportWidthBlocked(m_defaultSize.width());
     setExportHeightBlocked(m_defaultSize.height());
 }

 void ExportDialog::setExportWidthBlocked(int width)
 {
     if (m_widthSpinBox->value() != width) {
         const bool blockSignals = m_widthSpinBox->blockSignals(true);
         m_widthSpinBox->setValue(width);
         m_widthSpinBox->blockSignals(blockSignals);
     }
 }

 void ExportDialog::setExportHeightBlocked(int height)
 {
     if (m_heightSpinBox->value() != height) {
         const bool blockSignals = m_heightSpinBox->blockSignals(true);
         m_heightSpinBox->setValue(height);
         m_heightSpinBox->blockSignals(blockSignals);
     }
 }

 void ExportDialog::exportWidthChanged(int width)
 {
     const bool square = m_defaultSize.width() == m_defaultSize.height();
     setExportHeightBlocked(square ? width : qRound(qreal(width) / m_aspectRatio));
 }

 void ExportDialog::exportHeightChanged(int height)
 {
     const bool square = m_defaultSize.width() == m_defaultSize.height();
     setExportWidthBlocked(square ? height : qRound(qreal(height) * m_aspectRatio));
 }

 QString ExportDialog::exportFileName() const
 {
     return QDir::cleanPath(m_fileNameLineEdit->text().trimmed());
 }

 void ExportDialog::setExportFileName(const QString &f)
 {
     m_fileNameLineEdit->setText(QDir::toNativeSeparators(f));
 }

 void ExportDialog::browse()
 {
     QFileDialog fileDialog(this);
     fileDialog.setAcceptMode(QFileDialog::AcceptSave);
     const QString fileName = exportFileName();
     if (!fileName.isEmpty())
         fileDialog.setDirectory(QFileInfo(fileName).absolutePath());
     QStringList mimeTypes;
     const auto supportedMimeTypes = QImageWriter::supportedMimeTypes();
     for (const QByteArray &mimeType : supportedMimeTypes)
         mimeTypes.append(QLatin1String(mimeType));
     fileDialog.setMimeTypeFilters(mimeTypes);
     const int pngIndex = mimeTypes.indexOf("image/png");
     if (pngIndex >= 0) {
         fileDialog.selectMimeTypeFilter(mimeTypes.at(pngIndex));
         fileDialog.setDefaultSuffix("png");
     }
     if (fileDialog.exec() == QDialog::Accepted)
         setExportFileName(fileDialog.selectedFiles().constFirst());
 }