mainwindow.cpp Example File | Qt Widgets 5.12.6

Qt 5.12 | Qt Widgets | Finger Paint Example | mainwindow.cpp Example File

Qt 5.12.6 Reference Documentation

# mainwindow.cpp Example File

touch/fingerpaint/mainwindow.cpp

      /****************************************************************************
      **
      ** Copyright (C) 2016 The Qt Company Ltd.
      ** Contact: https://www.qt.io/licensing/
      **
      ** This file is part of the examples of the Qt Toolkit.
      **
      ** $QT_BEGIN_LICENSE:BSD$
      ** Commercial License Usage
      ** Licensees holding valid commercial Qt licenses may use this file in
      ** accordance with the commercial license agreement provided with the
      ** Software or, alternatively, in accordance with the terms contained in
      ** a written agreement between you and The Qt Company. For licensing terms
      ** and conditions see https://www.qt.io/terms-conditions. For further
      ** information use the contact form at https://www.qt.io/contact-us.
      **
      ** BSD License Usage
      ** Alternatively, you may use this file under the terms of the BSD license
      ** as follows:
      **
      ** "Redistribution and use in source and binary forms, with or without
      ** modification, are permitted provided that the following conditions are
      ** met:
      **   * Redistributions of source code must retain the above copyright
      **     notice, this list of conditions and the following disclaimer.
      **   * Redistributions in binary form must reproduce the above copyright
      **     notice, this list of conditions and the following disclaimer in
      **     the documentation and/or other materials provided with the
      **     distribution.
      **   * Neither the name of The Qt Company Ltd nor the names of its
      **     contributors may be used to endorse or promote products derived
      **     from this software without specific prior written permission.
      **
      **
      ** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
      ** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
      ** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
      ** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
      ** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
      ** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
      ** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
      ** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
      ** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
      ** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
      ** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
      **
      ** $QT_END_LICENSE$
      **
      ****************************************************************************/

      #include <QtWidgets>

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

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

          createActions();
          createMenus();

          setWindowTitle(tr("Finger Paint"));
          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::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->setShortcut(tr("Ctrl+O"));
          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->setShortcut(tr("Ctrl+Q"));
          connect(exitAct, SIGNAL(triggered()), this, SLOT(close()));

          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(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());
          }
      }