[Qt official routine study notes] Getting Started Programming with Qt Widgets

Create a QApplication object to manage application resources that are necessary for any uses Qt Widgets program. For there is no GUI application using Qt Widgets can be used QGuiApplication instead.

QApplication :: exec () into the event loop. Qt application is running, it will produce the event and sent to the widgets of the application. Event Example: mouse clicks and keyboard input.

https://doc.qt.io/qt-5/application-windows.html

https://doc.qt.io/qt-5/eventsandfilters.html

When you open a file error occurs, a warning message:

      if (!file.open(QIODevice::ReadOnly | QFile::Text)) {
          QMessageBox::warning(this, "Warning", "Cannot open file: " + file.errorString());
          return;
      }

All characters get the file:

      setWindowTitle(fileName);
      QTextStream in(&file);
      QString text = in.readAll();

Save all characters to the file

      QFile file(fileName);
      if (!file.open(QIODevice::WriteOnly | QFile::Text)) {
          QMessageBox::warning(this, "Warning", "Cannot save file: " + file.errorString());
          return;
      }
      setWindowTitle(fileName);
      QTextStream out(&file);
      QString text = ui->textEdit->toPlainText();
      out << text;
      file.close();

Printing Support:

qtHaveModule(printsupport): QT += printsupport
requires(qtConfig(fontdialog))

#if defined(QT_PRINTSUPPORT_LIB)
#include <QtPrintSupport/qtprintsupportglobal.h>
#if QT_CONFIG(printer)
#if QT_CONFIG(printdialog)
#include <QPrintDialog>
#endif // QT_CONFIG(printdialog)
#include <QPrinter>
#endif // QT_CONFIG(printer)
#endif // QT_PRINTSUPPORT_LIB

...

void Notepad::print()
{
#if QT_CONFIG(printer)
    QPrinter printDev;
#if QT_CONFIG(printdialog)
    QPrintDialog dialog(&printDev, this);
    if (dialog.exec() == QDialog::Rejected)
        return;
#endif // QT_CONFIG(printdialog)
    ui->textEdit->print(&printDev);
#endif // QT_CONFIG(printer)
}

Copy, Cut, Paste

void Notepad::copy()
{
#if QT_CONFIG(clipboard)
    ui->textEdit->copy();
#endif
}

void Notepad::cut()
{
#if QT_CONFIG(clipboard)
    ui->textEdit->cut();
#endif
}

void Notepad::paste()
{
#if QT_CONFIG(clipboard)
    ui->textEdit->paste();
#endif
}

Undo and Redo

void Notepad::undo()
{
     ui->textEdit->undo();
}

void Notepad::redo()
{
    ui->textEdit->redo();
}

When you set font and italics / bold, etc., set in italics / bold, select the text can only take effect:

void Notepad::selectFont()
{
    bool fontSelected;
    QFont font = QFontDialog::getFont(&fontSelected, this);
    if (fontSelected)
        ui->textEdit->setFont(font);
}

void Notepad::setFontUnderline(bool underline)
{
    ui->textEdit->setFontUnderline(underline);
}

void Notepad::setFontItalic(bool italic)
{
    ui->textEdit->setFontItalic(italic);
}

void Notepad::setFontBold(bool bold)
{
    bold ? ui->textEdit->setFontWeight(QFont::Bold) :
           ui->textEdit->setFontWeight(QFont::Normal);
}

About dialog:

void Notepad::about()
{
   QMessageBox::about(this, tr("About MDI"),
                tr("The <b>Notepad</b> example demonstrates how to code a basic "
                   "text editor using QtWidgets"));

}

[Qt official routine study notes] Getting Started Programming with Qt Widgets

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