Qt 5.11 | Qt Widgets | Scribble Example | mainwindow.cpp Example File

Qt 5.11.3 Reference Documentation

# mainwindow.cpp Example File

widgets/scribble/mainwindow.cpp

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      #include <QtWidgets>

      #include "mainwindow.h"
      #include "scribblearea.h"

      MainWindow::MainWindow()
      {
          scribbleArea = new ScribbleArea;
          setCentralWidget(scribbleArea);

          createActions();
          createMenus();

          setWindowTitle(tr("Scribble"));
          resize(500, 500);
      }

      void MainWindow::closeEvent(QCloseEvent *event)
      {
          if (maybeSave()) {
              event->accept();
          } else {
              event->ignore();
          }
      }

      void MainWindow::open()
      {
          if (maybeSave()) {
              QString fileName = QFileDialog::getOpenFileName(this,
                                         tr("Open File"), QDir::currentPath());
              if (!fileName.isEmpty())
                  scribbleArea->openImage(fileName);
          }
      }

      void MainWindow::save()
      {
          QAction *action = qobject_cast<QAction *>(sender());
          QByteArray fileFormat = action->data().toByteArray();
          saveFile(fileFormat);
      }

      void MainWindow::penColor()
      {
          QColor newColor = QColorDialog::getColor(scribbleArea->penColor());
          if (newColor.isValid())
              scribbleArea->setPenColor(newColor);
      }

      void MainWindow::penWidth()
      {
          bool ok;
          int newWidth = QInputDialog::getInt(this, tr("Scribble"),
                                              tr("Select pen width:"),
                                              scribbleArea->penWidth(),
                                              1, 50, 1, &ok);
          if (ok)
              scribbleArea->setPenWidth(newWidth);
      }

      void MainWindow::about()
      {
          QMessageBox::about(this, tr("About Scribble"),
                  tr("<p>The <b>Scribble</b> example shows how to use QMainWindow as the "
                     "base widget for an application, and how to reimplement some of "
                     "QWidget's event handlers to receive the events generated for "
                     "the application's widgets:</p><p> We reimplement the mouse event "
                     "handlers to facilitate drawing, the paint event handler to "
                     "update the application and the resize event handler to optimize "
                     "the application's appearance. In addition we reimplement the "
                     "close event handler to intercept the close events before "
                     "terminating the application.</p><p> The example also demonstrates "
                     "how to use QPainter to draw an image in real time, as well as "
                     "to repaint widgets.</p>"));
      }

      void MainWindow::createActions()
      {
          openAct = new QAction(tr("&Open..."), this);
          openAct->setShortcuts(QKeySequence::Open);
          connect(openAct, SIGNAL(triggered()), this, SLOT(open()));

          foreach (QByteArray format, QImageWriter::supportedImageFormats()) {
              QString text = tr("%1...").arg(QString(format).toUpper());

              QAction *action = new QAction(text, this);
              action->setData(format);
              connect(action, SIGNAL(triggered()), this, SLOT(save()));
              saveAsActs.append(action);
          }

          printAct = new QAction(tr("&Print..."), this);
          connect(printAct, SIGNAL(triggered()), scribbleArea, SLOT(print()));

          exitAct = new QAction(tr("E&xit"), this);
          exitAct->setShortcuts(QKeySequence::Quit);
          connect(exitAct, SIGNAL(triggered()), this, SLOT(close()));

          penColorAct = new QAction(tr("&Pen Color..."), this);
          connect(penColorAct, SIGNAL(triggered()), this, SLOT(penColor()));

          penWidthAct = new QAction(tr("Pen &Width..."), this);
          connect(penWidthAct, SIGNAL(triggered()), this, SLOT(penWidth()));

          clearScreenAct = new QAction(tr("&Clear Screen"), this);
          clearScreenAct->setShortcut(tr("Ctrl+L"));
          connect(clearScreenAct, SIGNAL(triggered()),
                  scribbleArea, SLOT(clearImage()));

          aboutAct = new QAction(tr("&About"), this);
          connect(aboutAct, SIGNAL(triggered()), this, SLOT(about()));

          aboutQtAct = new QAction(tr("About &Qt"), this);
          connect(aboutQtAct, SIGNAL(triggered()), qApp, SLOT(aboutQt()));
      }

      void MainWindow::createMenus()
      {
          saveAsMenu = new QMenu(tr("&Save As"), this);
          foreach (QAction *action, saveAsActs)
              saveAsMenu->addAction(action);

          fileMenu = new QMenu(tr("&File"), this);
          fileMenu->addAction(openAct);
          fileMenu->addMenu(saveAsMenu);
          fileMenu->addAction(printAct);
          fileMenu->addSeparator();
          fileMenu->addAction(exitAct);

          optionMenu = new QMenu(tr("&Options"), this);
          optionMenu->addAction(penColorAct);
          optionMenu->addAction(penWidthAct);
          optionMenu->addSeparator();
          optionMenu->addAction(clearScreenAct);

          helpMenu = new QMenu(tr("&Help"), this);
          helpMenu->addAction(aboutAct);
          helpMenu->addAction(aboutQtAct);

          menuBar()->addMenu(fileMenu);
          menuBar()->addMenu(optionMenu);
          menuBar()->addMenu(helpMenu);
      }

      bool MainWindow::maybeSave()
      {
          if (scribbleArea->isModified()) {
             QMessageBox::StandardButton ret;
             ret = QMessageBox::warning(this, tr("Scribble"),
                                tr("The image has been modified.\n"
                                   "Do you want to save your changes?"),
                                QMessageBox::Save | QMessageBox::Discard
                                | QMessageBox::Cancel);
              if (ret == QMessageBox::Save) {
                  return saveFile("png");
              } else if (ret == QMessageBox::Cancel) {
                  return false;
              }
          }
          return true;
      }

      bool MainWindow::saveFile(const QByteArray &fileFormat)
      {
          QString initialPath = QDir::currentPath() + "/untitled." + fileFormat;

          QString fileName = QFileDialog::getSaveFileName(this, tr("Save As"),
                                     initialPath,
                                     tr("%1 Files (*.%2);;All Files (*)")
                                     .arg(QString::fromLatin1(fileFormat.toUpper()))
                                     .arg(QString::fromLatin1(fileFormat)));
          if (fileName.isEmpty()) {
              return false;
          } else {
              return scribbleArea->saveImage(fileName, fileFormat.constData());
          }
      }