mainwindow.cpp Example File

  /****************************************************************************
  **
  ** 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("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());
      }
  }