Qt Reference Documentation

# mainwindow.cpp Example File

mainwindows/application/mainwindow.cpp

     /****************************************************************************
     **
     ** Copyright (C) 2012 Nokia Corporation and/or its subsidiary(-ies).
     ** All rights reserved.
     ** Contact: Nokia Corporation (qt-info@nokia.com)
     **
     ** This file is part of the examples of the Qt Toolkit.
     **
     ** $QT_BEGIN_LICENSE:BSD$
     ** 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 Nokia Corporation and its Subsidiary(-ies) 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 <QtGui>

     #include "mainwindow.h"

     MainWindow::MainWindow()
     {
         textEdit = new QPlainTextEdit;
         setCentralWidget(textEdit);

         createActions();
         createMenus();
         createToolBars();
         createStatusBar();

         readSettings();

         connect(textEdit->document(), SIGNAL(contentsChanged()),
                 this, SLOT(documentWasModified()));

         setCurrentFile("");
         setUnifiedTitleAndToolBarOnMac(true);
     }

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

     void MainWindow::newFile()
     {
         if (maybeSave()) {
             textEdit->clear();
             setCurrentFile("");
         }
     }

     void MainWindow::open()
     {
         if (maybeSave()) {
             QString fileName = QFileDialog::getOpenFileName(this);
             if (!fileName.isEmpty())
                 loadFile(fileName);
         }
     }

     bool MainWindow::save()
     {
         if (curFile.isEmpty()) {
             return saveAs();
         } else {
             return saveFile(curFile);
         }
     }

     bool MainWindow::saveAs()
     {
         QString fileName = QFileDialog::getSaveFileName(this);
         if (fileName.isEmpty())
             return false;

         return saveFile(fileName);
     }

     void MainWindow::about()
     {
        QMessageBox::about(this, tr("About Application"),
                 tr("The <b>Application</b> example demonstrates how to "
                    "write modern GUI applications using Qt, with a menu bar, "
                    "toolbars, and a status bar."));
     }

     void MainWindow::documentWasModified()
     {
         setWindowModified(textEdit->document()->isModified());
     }

     void MainWindow::createActions()
     {
         newAct = new QAction(QIcon(":/images/new.png"), tr("&New"), this);
         newAct->setShortcuts(QKeySequence::New);
         newAct->setStatusTip(tr("Create a new file"));
         connect(newAct, SIGNAL(triggered()), this, SLOT(newFile()));

         openAct = new QAction(QIcon(":/images/open.png"), tr("&Open..."), this);
         openAct->setShortcuts(QKeySequence::Open);
         openAct->setStatusTip(tr("Open an existing file"));
         connect(openAct, SIGNAL(triggered()), this, SLOT(open()));

         saveAct = new QAction(QIcon(":/images/save.png"), tr("&Save"), this);
         saveAct->setShortcuts(QKeySequence::Save);
         saveAct->setStatusTip(tr("Save the document to disk"));
         connect(saveAct, SIGNAL(triggered()), this, SLOT(save()));

         saveAsAct = new QAction(tr("Save &As..."), this);
         saveAsAct->setShortcuts(QKeySequence::SaveAs);
         saveAsAct->setStatusTip(tr("Save the document under a new name"));
         connect(saveAsAct, SIGNAL(triggered()), this, SLOT(saveAs()));

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

         cutAct = new QAction(QIcon(":/images/cut.png"), tr("Cu&t"), this);
         cutAct->setShortcuts(QKeySequence::Cut);
         cutAct->setStatusTip(tr("Cut the current selection's contents to the "
                                 "clipboard"));
         connect(cutAct, SIGNAL(triggered()), textEdit, SLOT(cut()));

         copyAct = new QAction(QIcon(":/images/copy.png"), tr("&Copy"), this);
         copyAct->setShortcuts(QKeySequence::Copy);
         copyAct->setStatusTip(tr("Copy the current selection's contents to the "
                                  "clipboard"));
         connect(copyAct, SIGNAL(triggered()), textEdit, SLOT(copy()));

         pasteAct = new QAction(QIcon(":/images/paste.png"), tr("&Paste"), this);
         pasteAct->setShortcuts(QKeySequence::Paste);
         pasteAct->setStatusTip(tr("Paste the clipboard's contents into the current "
                                   "selection"));
         connect(pasteAct, SIGNAL(triggered()), textEdit, SLOT(paste()));

         aboutAct = new QAction(tr("&About"), this);
         aboutAct->setStatusTip(tr("Show the application's About box"));
         connect(aboutAct, SIGNAL(triggered()), this, SLOT(about()));

         aboutQtAct = new QAction(tr("About &Qt"), this);
         aboutQtAct->setStatusTip(tr("Show the Qt library's About box"));
         connect(aboutQtAct, SIGNAL(triggered()), qApp, SLOT(aboutQt()));

         cutAct->setEnabled(false);
         copyAct->setEnabled(false);
         connect(textEdit, SIGNAL(copyAvailable(bool)),
                 cutAct, SLOT(setEnabled(bool)));
         connect(textEdit, SIGNAL(copyAvailable(bool)),
                 copyAct, SLOT(setEnabled(bool)));
     }

     void MainWindow::createMenus()
     {
         fileMenu = menuBar()->addMenu(tr("&File"));
         fileMenu->addAction(newAct);
         fileMenu->addAction(openAct);
         fileMenu->addAction(saveAct);
         fileMenu->addAction(saveAsAct);
         fileMenu->addSeparator();
         fileMenu->addAction(exitAct);

         editMenu = menuBar()->addMenu(tr("&Edit"));
         editMenu->addAction(cutAct);
         editMenu->addAction(copyAct);
         editMenu->addAction(pasteAct);

         menuBar()->addSeparator();

         helpMenu = menuBar()->addMenu(tr("&Help"));
         helpMenu->addAction(aboutAct);
         helpMenu->addAction(aboutQtAct);
     }

     void MainWindow::createToolBars()
     {
         fileToolBar = addToolBar(tr("File"));
         fileToolBar->addAction(newAct);
         fileToolBar->addAction(openAct);
         fileToolBar->addAction(saveAct);

         editToolBar = addToolBar(tr("Edit"));
         editToolBar->addAction(cutAct);
         editToolBar->addAction(copyAct);
         editToolBar->addAction(pasteAct);
     }

     void MainWindow::createStatusBar()
     {
         statusBar()->showMessage(tr("Ready"));
     }

     void MainWindow::readSettings()
     {
         QSettings settings("Trolltech", "Application Example");
         QPoint pos = settings.value("pos", QPoint(200, 200)).toPoint();
         QSize size = settings.value("size", QSize(400, 400)).toSize();
         resize(size);
         move(pos);
     }

     void MainWindow::writeSettings()
     {
         QSettings settings("Trolltech", "Application Example");
         settings.setValue("pos", pos());
         settings.setValue("size", size());
     }

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

     void MainWindow::loadFile(const QString &fileName)
     {
         QFile file(fileName);
         if (!file.open(QFile::ReadOnly | QFile::Text)) {
             QMessageBox::warning(this, tr("Application"),
                                  tr("Cannot read file %1:\n%2.")
                                  .arg(fileName)
                                  .arg(file.errorString()));
             return;
         }

         QTextStream in(&file);
     #ifndef QT_NO_CURSOR
         QApplication::setOverrideCursor(Qt::WaitCursor);
     #endif
         textEdit->setPlainText(in.readAll());
     #ifndef QT_NO_CURSOR
         QApplication::restoreOverrideCursor();
     #endif

         setCurrentFile(fileName);
         statusBar()->showMessage(tr("File loaded"), 2000);
     }

     bool MainWindow::saveFile(const QString &fileName)
     {
         QFile file(fileName);
         if (!file.open(QFile::WriteOnly | QFile::Text)) {
             QMessageBox::warning(this, tr("Application"),
                                  tr("Cannot write file %1:\n%2.")
                                  .arg(fileName)
                                  .arg(file.errorString()));
             return false;
         }

         QTextStream out(&file);
     #ifndef QT_NO_CURSOR
         QApplication::setOverrideCursor(Qt::WaitCursor);
     #endif
         out << textEdit->toPlainText();
     #ifndef QT_NO_CURSOR
         QApplication::restoreOverrideCursor();
     #endif

         setCurrentFile(fileName);
         statusBar()->showMessage(tr("File saved"), 2000);
         return true;
     }

     void MainWindow::setCurrentFile(const QString &fileName)
     {
         curFile = fileName;
         textEdit->document()->setModified(false);
         setWindowModified(false);

         QString shownName = curFile;
         if (curFile.isEmpty())
             shownName = "untitled.txt";
         setWindowFilePath(shownName);
     }

     QString MainWindow::strippedName(const QString &fullFileName)
     {
         return QFileInfo(fullFileName).fileName();
     }