C++/Qt/QMenu

Материал из C\C++ эксперт
Перейти к: навигация, поиск

Adding menu to window

  
/****************************************************************************
**
** Copyright (C) 2009 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.
**
** $QT_BEGIN_LICENSE:LGPL$
** Commercial Usage
** Licensees holding valid Qt Commercial licenses may use this file in
** accordance with the Qt Commercial License Agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and Nokia.
**
** GNU Lesser General Public License Usage
** Alternatively, this file may be used under the terms of the GNU Lesser
** General Public License version 2.1 as published by the Free Software
** Foundation and appearing in the file LICENSE.LGPL included in the
** packaging of this file.  Please review the following information to
** ensure the GNU Lesser General Public License version 2.1 requirements
** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
**
** In addition, as a special exception, Nokia gives you certain additional
** rights.  These rights are described in the Nokia Qt LGPL Exception
** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
**
** GNU General Public License Usage
** Alternatively, this file may be used under the terms of the GNU
** General Public License version 3.0 as published by the Free Software
** Foundation and appearing in the file LICENSE.GPL included in the
** packaging of this file.  Please review the following information to
** ensure the GNU General Public License version 3.0 requirements will be
** met: http://www.gnu.org/copyleft/gpl.html.
**
** If you have questions regarding the use of this file, please contact
** Nokia at qt-info@nokia.com.
** $QT_END_LICENSE$
**
****************************************************************************/
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
QT_BEGIN_NAMESPACE
class QAction;
class QActionGroup;
class QLabel;
class QMenu;
QT_END_NAMESPACE

class MainWindow : public QMainWindow
{
    Q_OBJECT
public:
    MainWindow();
protected:
    void contextMenuEvent(QContextMenuEvent *event);

private slots:
    void newFile();
    void open();
    void save();
    void print();
    void undo();
    void redo();
    void cut();
    void copy();
    void paste();
    void bold();
    void italic();
    void leftAlign();
    void rightAlign();
    void justify();
    void center();
    void setLineSpacing();
    void setParagraphSpacing();
    void about();
    void aboutQt();

private:
    void createActions();
    void createMenus();

    QMenu *fileMenu;
    QMenu *editMenu;
    QMenu *formatMenu;
    QMenu *helpMenu;
    QActionGroup *alignmentGroup;
    QAction *newAct;
    QAction *openAct;
    QAction *saveAct;
    QAction *printAct;
    QAction *exitAct;
    QAction *undoAct;
    QAction *redoAct;
    QAction *cutAct;
    QAction *copyAct;
    QAction *pasteAct;
    QAction *boldAct;
    QAction *italicAct;
    QAction *leftAlignAct;
    QAction *rightAlignAct;
    QAction *justifyAct;
    QAction *centerAct;
    QAction *setLineSpacingAct;
    QAction *setParagraphSpacingAct;
    QAction *aboutAct;
    QAction *aboutQtAct;
    QLabel *infoLabel;
};

#endif


#include <QtGui>
#include "mainwindow.h"

MainWindow::MainWindow()
{
    QWidget *widget = new QWidget;
    setCentralWidget(widget);

    QWidget *topFiller = new QWidget;
    topFiller->setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
    infoLabel = new QLabel(tr("<i>Choose a menu option, or right-click to "
                              "invoke a context menu</i>"));
    infoLabel->setFrameStyle(QFrame::StyledPanel | QFrame::Sunken);
    infoLabel->setAlignment(Qt::AlignCenter);
    QWidget *bottomFiller = new QWidget;
    bottomFiller->setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
    QVBoxLayout *layout = new QVBoxLayout;
    layout->setMargin(5);
    layout->addWidget(topFiller);
    layout->addWidget(infoLabel);
    layout->addWidget(bottomFiller);
    widget->setLayout(layout);

    createActions();
    createMenus();
    QString message = tr("A context menu is available by right-clicking");
    statusBar()->showMessage(message);
    setWindowTitle(tr("Menus"));
    setMinimumSize(160, 160);
    resize(480, 320);
}

void MainWindow::contextMenuEvent(QContextMenuEvent *event)
{
    QMenu menu(this);
    menu.addAction(cutAct);
    menu.addAction(copyAct);
    menu.addAction(pasteAct);
    menu.exec(event->globalPos());
}

void MainWindow::newFile()
{
    infoLabel->setText(tr("Invoked <b>File|New</b>"));
}
void MainWindow::open()
{
    infoLabel->setText(tr("Invoked <b>File|Open</b>"));
}
void MainWindow::save()
{
    infoLabel->setText(tr("Invoked <b>File|Save</b>"));
}
void MainWindow::print()
{
    infoLabel->setText(tr("Invoked <b>File|Print</b>"));
}
void MainWindow::undo()
{
    infoLabel->setText(tr("Invoked <b>Edit|Undo</b>"));
}
void MainWindow::redo()
{
    infoLabel->setText(tr("Invoked <b>Edit|Redo</b>"));
}
void MainWindow::cut()
{
    infoLabel->setText(tr("Invoked <b>Edit|Cut</b>"));
}
void MainWindow::copy()
{
    infoLabel->setText(tr("Invoked <b>Edit|Copy</b>"));
}
void MainWindow::paste()
{
    infoLabel->setText(tr("Invoked <b>Edit|Paste</b>"));
}
void MainWindow::bold()
{
    infoLabel->setText(tr("Invoked <b>Edit|Format|Bold</b>"));
}
void MainWindow::italic()
{
    infoLabel->setText(tr("Invoked <b>Edit|Format|Italic</b>"));
}
void MainWindow::leftAlign()
{
    infoLabel->setText(tr("Invoked <b>Edit|Format|Left Align</b>"));
}
void MainWindow::rightAlign()
{
    infoLabel->setText(tr("Invoked <b>Edit|Format|Right Align</b>"));
}
void MainWindow::justify()
{
    infoLabel->setText(tr("Invoked <b>Edit|Format|Justify</b>"));
}
void MainWindow::center()
{
    infoLabel->setText(tr("Invoked <b>Edit|Format|Center</b>"));
}
void MainWindow::setLineSpacing()
{
    infoLabel->setText(tr("Invoked <b>Edit|Format|Set Line Spacing</b>"));
}
void MainWindow::setParagraphSpacing()
{
    infoLabel->setText(tr("Invoked <b>Edit|Format|Set Paragraph Spacing</b>"));
}
void MainWindow::about()
{
    infoLabel->setText(tr("Invoked <b>Help|About</b>"));
    QMessageBox::about(this, tr("About Menu"),
            tr("The <b>Menu</b> example shows how to create "
               "menu-bar menus and context menus."));
}
void MainWindow::aboutQt()
{
    infoLabel->setText(tr("Invoked <b>Help|About Qt</b>"));
}

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

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

    saveAct = new QAction(tr("&Save"), this);
    saveAct->setShortcuts(QKeySequence::Save);
    saveAct->setStatusTip(tr("Save the document to disk"));
    connect(saveAct, SIGNAL(triggered()), this, SLOT(save()));
    printAct = new QAction(tr("&Print..."), this);
    printAct->setShortcuts(QKeySequence::Print);
    printAct->setStatusTip(tr("Print the document"));
    connect(printAct, SIGNAL(triggered()), this, SLOT(print()));
    exitAct = new QAction(tr("E&xit"), this);
    exitAct->setShortcut(tr("Ctrl+Q"));
    exitAct->setStatusTip(tr("Exit the application"));
    connect(exitAct, SIGNAL(triggered()), this, SLOT(close()));
    undoAct = new QAction(tr("&Undo"), this);
    undoAct->setShortcuts(QKeySequence::Undo);
    undoAct->setStatusTip(tr("Undo the last operation"));
    connect(undoAct, SIGNAL(triggered()), this, SLOT(undo()));
    redoAct = new QAction(tr("&Redo"), this);
    redoAct->setShortcuts(QKeySequence::Redo);
    redoAct->setStatusTip(tr("Redo the last operation"));
    connect(redoAct, SIGNAL(triggered()), this, SLOT(redo()));
    cutAct = new QAction(tr("Cu&t"), this);
    cutAct->setShortcuts(QKeySequence::Cut);
    cutAct->setStatusTip(tr("Cut the current selection"s contents to the "
                            "clipboard"));
    connect(cutAct, SIGNAL(triggered()), this, SLOT(cut()));
    copyAct = new QAction(tr("&Copy"), this);
    copyAct->setShortcut(tr("Ctrl+C"));
    copyAct->setStatusTip(tr("Copy the current selection"s contents to the "
                             "clipboard"));
    connect(copyAct, SIGNAL(triggered()), this, SLOT(copy()));
    pasteAct = new QAction(tr("&Paste"), this);
    pasteAct->setShortcuts(QKeySequence::Paste);
    pasteAct->setStatusTip(tr("Paste the clipboard"s contents into the current "
                              "selection"));
    connect(pasteAct, SIGNAL(triggered()), this, SLOT(paste()));
    boldAct = new QAction(tr("&Bold"), this);
    boldAct->setCheckable(true);
    boldAct->setShortcut(tr("Ctrl+B"));
    boldAct->setStatusTip(tr("Make the text bold"));
    connect(boldAct, SIGNAL(triggered()), this, SLOT(bold()));
    QFont boldFont = boldAct->font();
    boldFont.setBold(true);
    boldAct->setFont(boldFont);
    italicAct = new QAction(tr("&Italic"), this);
    italicAct->setCheckable(true);
    italicAct->setShortcut(tr("Ctrl+I"));
    italicAct->setStatusTip(tr("Make the text italic"));
    connect(italicAct, SIGNAL(triggered()), this, SLOT(italic()));
    QFont italicFont = italicAct->font();
    italicFont.setItalic(true);
    italicAct->setFont(italicFont);
    setLineSpacingAct = new QAction(tr("Set &Line Spacing..."), this);
    setLineSpacingAct->setStatusTip(tr("Change the gap between the lines of a "
                                       "paragraph"));
    connect(setLineSpacingAct, SIGNAL(triggered()), this, SLOT(setLineSpacing()));
    setParagraphSpacingAct = new QAction(tr("Set &Paragraph Spacing..."), this);
    setLineSpacingAct->setStatusTip(tr("Change the gap between paragraphs"));
    connect(setParagraphSpacingAct, SIGNAL(triggered()),
            this, SLOT(setParagraphSpacing()));
    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()));
    connect(aboutQtAct, SIGNAL(triggered()), this, SLOT(aboutQt()));
    leftAlignAct = new QAction(tr("&Left Align"), this);
    leftAlignAct->setCheckable(true);
    leftAlignAct->setShortcut(tr("Ctrl+L"));
    leftAlignAct->setStatusTip(tr("Left align the selected text"));
    connect(leftAlignAct, SIGNAL(triggered()), this, SLOT(leftAlign()));
    rightAlignAct = new QAction(tr("&Right Align"), this);
    rightAlignAct->setCheckable(true);
    rightAlignAct->setShortcut(tr("Ctrl+R"));
    rightAlignAct->setStatusTip(tr("Right align the selected text"));
    connect(rightAlignAct, SIGNAL(triggered()), this, SLOT(rightAlign()));
    justifyAct = new QAction(tr("&Justify"), this);
    justifyAct->setCheckable(true);
    justifyAct->setShortcut(tr("Ctrl+J"));
    justifyAct->setStatusTip(tr("Justify the selected text"));
    connect(justifyAct, SIGNAL(triggered()), this, SLOT(justify()));
    centerAct = new QAction(tr("&Center"), this);
    centerAct->setCheckable(true);
    centerAct->setShortcut(tr("Ctrl+E"));
    centerAct->setStatusTip(tr("Center the selected text"));
    connect(centerAct, SIGNAL(triggered()), this, SLOT(center()));
 
    alignmentGroup = new QActionGroup(this);
    alignmentGroup->addAction(leftAlignAct);
    alignmentGroup->addAction(rightAlignAct);
    alignmentGroup->addAction(justifyAct);
    alignmentGroup->addAction(centerAct);
    leftAlignAct->setChecked(true);
}

void MainWindow::createMenus()
{
 
    fileMenu = menuBar()->addMenu(tr("&File"));
    fileMenu->addAction(newAct);
    fileMenu->addAction(openAct);
    fileMenu->addAction(saveAct);
    fileMenu->addAction(printAct);
    fileMenu->addSeparator();
    fileMenu->addAction(exitAct);
    editMenu = menuBar()->addMenu(tr("&Edit"));
    editMenu->addAction(undoAct);
    editMenu->addAction(redoAct);
    editMenu->addSeparator();
    editMenu->addAction(cutAct);
    editMenu->addAction(copyAct);
    editMenu->addAction(pasteAct);
    editMenu->addSeparator();
    helpMenu = menuBar()->addMenu(tr("&Help"));
    helpMenu->addAction(aboutAct);
    helpMenu->addAction(aboutQtAct);

    formatMenu = editMenu->addMenu(tr("&Format"));
    formatMenu->addAction(boldAct);
    formatMenu->addAction(italicAct);
    formatMenu->addSeparator()->setText(tr("Alignment"));
    formatMenu->addAction(leftAlignAct);
    formatMenu->addAction(rightAlignAct);
    formatMenu->addAction(justifyAct);
    formatMenu->addAction(centerAct);
    formatMenu->addSeparator();
    formatMenu->addAction(setLineSpacingAct);
    formatMenu->addAction(setParagraphSpacingAct);
}



#include <QApplication>
#include "mainwindow.h"
int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    MainWindow window;
    window.show();
    return app.exec();
}


Image viewer

  
/****************************************************************************
**
** Copyright (C) 2009 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.
**
** $QT_BEGIN_LICENSE:LGPL$
** Commercial Usage
** Licensees holding valid Qt Commercial licenses may use this file in
** accordance with the Qt Commercial License Agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and Nokia.
**
** GNU Lesser General Public License Usage
** Alternatively, this file may be used under the terms of the GNU Lesser
** General Public License version 2.1 as published by the Free Software
** Foundation and appearing in the file LICENSE.LGPL included in the
** packaging of this file.  Please review the following information to
** ensure the GNU Lesser General Public License version 2.1 requirements
** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
**
** In addition, as a special exception, Nokia gives you certain additional
** rights.  These rights are described in the Nokia Qt LGPL Exception
** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
**
** GNU General Public License Usage
** Alternatively, this file may be used under the terms of the GNU
** General Public License version 3.0 as published by the Free Software
** Foundation and appearing in the file LICENSE.GPL included in the
** packaging of this file.  Please review the following information to
** ensure the GNU General Public License version 3.0 requirements will be
** met: http://www.gnu.org/copyleft/gpl.html.
**
** If you have questions regarding the use of this file, please contact
** Nokia at qt-info@nokia.com.
** $QT_END_LICENSE$
**
****************************************************************************/
#ifndef IMAGEVIEWER_H
#define IMAGEVIEWER_H
#include <QMainWindow>
#include <QPrinter>
QT_BEGIN_NAMESPACE
class QAction;
class QLabel;
class QMenu;
class QScrollArea;
class QScrollBar;
QT_END_NAMESPACE

class ImageViewer : public QMainWindow
{
    Q_OBJECT
public:
    ImageViewer();
private slots:
    void open();
    void print();
    void zoomIn();
    void zoomOut();
    void normalSize();
    void fitToWindow();
    void about();
private:
    void createActions();
    void createMenus();
    void updateActions();
    void scaleImage(double factor);
    void adjustScrollBar(QScrollBar *scrollBar, double factor);
    QLabel *imageLabel;
    QScrollArea *scrollArea;
    double scaleFactor;
#ifndef QT_NO_PRINTER
    QPrinter printer;
#endif
    QAction *openAct;
    QAction *printAct;
    QAction *exitAct;
    QAction *zoomInAct;
    QAction *zoomOutAct;
    QAction *normalSizeAct;
    QAction *fitToWindowAct;
    QAction *aboutAct;
    QAction *aboutQtAct;
    QMenu *fileMenu;
    QMenu *viewMenu;
    QMenu *helpMenu;
};

#endif



#include <QtGui>
#include "imageviewer.h"

ImageViewer::ImageViewer()
{
    imageLabel = new QLabel;
    imageLabel->setBackgroundRole(QPalette::Base);
    imageLabel->setSizePolicy(QSizePolicy::Ignored, QSizePolicy::Ignored);
    imageLabel->setScaledContents(true);
    scrollArea = new QScrollArea;
    scrollArea->setBackgroundRole(QPalette::Dark);
    scrollArea->setWidget(imageLabel);
    setCentralWidget(scrollArea);
    createActions();
    createMenus();
    setWindowTitle(tr("Image Viewer"));
    resize(500, 400);
}

void ImageViewer::open()
 
{
    QString fileName = QFileDialog::getOpenFileName(this,
                                    tr("Open File"), QDir::currentPath());
    if (!fileName.isEmpty()) {
        QImage image(fileName);
        if (image.isNull()) {
            QMessageBox::information(this, tr("Image Viewer"),
                                     tr("Cannot load %1.").arg(fileName));
            return;
        }
 
        imageLabel->setPixmap(QPixmap::fromImage(image));
 
        scaleFactor = 1.0;
        printAct->setEnabled(true);
        fitToWindowAct->setEnabled(true);
        updateActions();
        if (!fitToWindowAct->isChecked())
            imageLabel->adjustSize();
    }
}

void ImageViewer::print()
 
{
    Q_ASSERT(imageLabel->pixmap());
#ifndef QT_NO_PRINTER
 
    QPrintDialog dialog(&printer, this);
 
    if (dialog.exec()) {
        QPainter painter(&printer);
        QRect rect = painter.viewport();
        QSize size = imageLabel->pixmap()->size();
        size.scale(rect.size(), Qt::KeepAspectRatio);
        painter.setViewport(rect.x(), rect.y(), size.width(), size.height());
        painter.setWindow(imageLabel->pixmap()->rect());
        painter.drawPixmap(0, 0, *imageLabel->pixmap());
    }
#endif
}

void ImageViewer::zoomIn()
 
{
    scaleImage(1.25);
}
void ImageViewer::zoomOut()
{
    scaleImage(0.8);
}
 
void ImageViewer::normalSize()
 
{
    imageLabel->adjustSize();
    scaleFactor = 1.0;
}

void ImageViewer::fitToWindow()
 
{
    bool fitToWindow = fitToWindowAct->isChecked();
    scrollArea->setWidgetResizable(fitToWindow);
    if (!fitToWindow) {
        normalSize();
    }
    updateActions();
}


void ImageViewer::about()
 
{
    QMessageBox::about(this, tr("About Image Viewer"),
            tr("<p>The <b>Image Viewer</b> example shows how to combine QLabel "
               "and QScrollArea to display an image. QLabel is typically used "
               "for displaying a text, but it can also display an image. "
               "QScrollArea provides a scrolling view around another widget. "
               "If the child widget exceeds the size of the frame, QScrollArea "
               "automatically provides scroll bars. </p><p>The example "
               "demonstrates how QLabel"s ability to scale its contents "
               "(QLabel::scaledContents), and QScrollArea"s ability to "
               "automatically resize its contents "
               "(QScrollArea::widgetResizable), can be used to implement "
               "zooming and scaling features. </p><p>In addition the example "
               "shows how to use QPainter to print an image.</p>"));
}

void ImageViewer::createActions()
 
{
    openAct = new QAction(tr("&Open..."), this);
    openAct->setShortcut(tr("Ctrl+O"));
    connect(openAct, SIGNAL(triggered()), this, SLOT(open()));
    printAct = new QAction(tr("&Print..."), this);
    printAct->setShortcut(tr("Ctrl+P"));
    printAct->setEnabled(false);
    connect(printAct, SIGNAL(triggered()), this, SLOT(print()));
    exitAct = new QAction(tr("E&xit"), this);
    exitAct->setShortcut(tr("Ctrl+Q"));
    connect(exitAct, SIGNAL(triggered()), this, SLOT(close()));
    zoomInAct = new QAction(tr("Zoom &In (25%)"), this);
    zoomInAct->setShortcut(tr("Ctrl++"));
    zoomInAct->setEnabled(false);
    connect(zoomInAct, SIGNAL(triggered()), this, SLOT(zoomIn()));
    zoomOutAct = new QAction(tr("Zoom &Out (25%)"), this);
    zoomOutAct->setShortcut(tr("Ctrl+-"));
    zoomOutAct->setEnabled(false);
    connect(zoomOutAct, SIGNAL(triggered()), this, SLOT(zoomOut()));
    normalSizeAct = new QAction(tr("&Normal Size"), this);
    normalSizeAct->setShortcut(tr("Ctrl+S"));
    normalSizeAct->setEnabled(false);
    connect(normalSizeAct, SIGNAL(triggered()), this, SLOT(normalSize()));
    fitToWindowAct = new QAction(tr("&Fit to Window"), this);
    fitToWindowAct->setEnabled(false);
    fitToWindowAct->setCheckable(true);
    fitToWindowAct->setShortcut(tr("Ctrl+F"));
    connect(fitToWindowAct, SIGNAL(triggered()), this, SLOT(fitToWindow()));
    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 ImageViewer::createMenus()
 
{
    fileMenu = new QMenu(tr("&File"), this);
    fileMenu->addAction(openAct);
    fileMenu->addAction(printAct);
    fileMenu->addSeparator();
    fileMenu->addAction(exitAct);
    viewMenu = new QMenu(tr("&View"), this);
    viewMenu->addAction(zoomInAct);
    viewMenu->addAction(zoomOutAct);
    viewMenu->addAction(normalSizeAct);
    viewMenu->addSeparator();
    viewMenu->addAction(fitToWindowAct);
    helpMenu = new QMenu(tr("&Help"), this);
    helpMenu->addAction(aboutAct);
    helpMenu->addAction(aboutQtAct);
    menuBar()->addMenu(fileMenu);
    menuBar()->addMenu(viewMenu);
    menuBar()->addMenu(helpMenu);
}

void ImageViewer::updateActions()
 
{
    zoomInAct->setEnabled(!fitToWindowAct->isChecked());
    zoomOutAct->setEnabled(!fitToWindowAct->isChecked());
    normalSizeAct->setEnabled(!fitToWindowAct->isChecked());
}

void ImageViewer::scaleImage(double factor)
 
{
    Q_ASSERT(imageLabel->pixmap());
    scaleFactor *= factor;
    imageLabel->resize(scaleFactor * imageLabel->pixmap()->size());
    adjustScrollBar(scrollArea->horizontalScrollBar(), factor);
    adjustScrollBar(scrollArea->verticalScrollBar(), factor);
    zoomInAct->setEnabled(scaleFactor < 3.0);
    zoomOutAct->setEnabled(scaleFactor > 0.333);
}

void ImageViewer::adjustScrollBar(QScrollBar *scrollBar, double factor)
 
{
    scrollBar->setValue(int(factor * scrollBar->value()
                            + ((factor - 1) * scrollBar->pageStep()/2)));
}


#include <QApplication>
#include "imageviewer.h"
int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    ImageViewer imageViewer;
    imageViewer.show();
    return app.exec();
}


Recent file menu

  
/****************************************************************************
**
** Copyright (C) 2009 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.
**
** $QT_BEGIN_LICENSE:LGPL$
** Commercial Usage
** Licensees holding valid Qt Commercial licenses may use this file in
** accordance with the Qt Commercial License Agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and Nokia.
**
** GNU Lesser General Public License Usage
** Alternatively, this file may be used under the terms of the GNU Lesser
** General Public License version 2.1 as published by the Free Software
** Foundation and appearing in the file LICENSE.LGPL included in the
** packaging of this file.  Please review the following information to
** ensure the GNU Lesser General Public License version 2.1 requirements
** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
**
** In addition, as a special exception, Nokia gives you certain additional
** rights.  These rights are described in the Nokia Qt LGPL Exception
** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
**
** GNU General Public License Usage
** Alternatively, this file may be used under the terms of the GNU
** General Public License version 3.0 as published by the Free Software
** Foundation and appearing in the file LICENSE.GPL included in the
** packaging of this file.  Please review the following information to
** ensure the GNU General Public License version 3.0 requirements will be
** met: http://www.gnu.org/copyleft/gpl.html.
**
** If you have questions regarding the use of this file, please contact
** Nokia at qt-info@nokia.com.
** $QT_END_LICENSE$
**
****************************************************************************/
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QList>
#include <QMainWindow>
QT_BEGIN_NAMESPACE
class QAction;
class QMenu;
class QTextEdit;
QT_END_NAMESPACE
class MainWindow : public QMainWindow
{
    Q_OBJECT
public:
    MainWindow();
private slots:
    void newFile();
    void open();
    void save();
    void saveAs();
    void openRecentFile();
    void about();
private:
    void createActions();
    void createMenus();
    void loadFile(const QString &fileName);
    void saveFile(const QString &fileName);
    void setCurrentFile(const QString &fileName);
    void updateRecentFileActions();
    QString strippedName(const QString &fullFileName);
    QString curFile;
    QTextEdit *textEdit;
    QMenu *fileMenu;
    QMenu *recentFilesMenu;
    QMenu *helpMenu;
    QAction *newAct;
    QAction *openAct;
    QAction *saveAct;
    QAction *saveAsAct;
    QAction *exitAct;
    QAction *aboutAct;
    QAction *aboutQtAct;
    QAction *separatorAct;
    enum { MaxRecentFiles = 5 };
    QAction *recentFileActs[MaxRecentFiles];
};
#endif


#include <QtGui>
#include "mainwindow.h"
MainWindow::MainWindow()
{
    setAttribute(Qt::WA_DeleteOnClose);
    textEdit = new QTextEdit;
    setCentralWidget(textEdit);
    createActions();
    createMenus();
    (void)statusBar();
    setWindowTitle(tr("Recent Files"));
    resize(400, 300);
}
void MainWindow::newFile()
{
    MainWindow *other = new MainWindow;
    other->show();
}
void MainWindow::open()
{
    QString fileName = QFileDialog::getOpenFileName(this);
    if (!fileName.isEmpty())
        loadFile(fileName);
}
void MainWindow::save()
{
    if (curFile.isEmpty())
        saveAs();
    else
        saveFile(curFile);
}
void MainWindow::saveAs()
{
    QString fileName = QFileDialog::getSaveFileName(this);
    if (fileName.isEmpty())
        return;
    saveFile(fileName);
}
void MainWindow::openRecentFile()
{
    QAction *action = qobject_cast<QAction *>(sender());
    if (action)
        loadFile(action->data().toString());
}
void MainWindow::about()
{
   QMessageBox::about(this, tr("About Recent Files"),
            tr("The <b>Recent Files</b> example demonstrates how to provide a "
               "recently used file menu in a Qt application."));
}
void MainWindow::createActions()
{
    newAct = new QAction(tr("&New"), this);
    newAct->setShortcuts(QKeySequence::New);
    newAct->setStatusTip(tr("Create a new file"));
    connect(newAct, SIGNAL(triggered()), this, SLOT(newFile()));
    openAct = new QAction(tr("&Open..."), this);
    openAct->setShortcuts(QKeySequence::Open);
    openAct->setStatusTip(tr("Open an existing file"));
    connect(openAct, SIGNAL(triggered()), this, SLOT(open()));
    saveAct = new QAction(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()));
    for (int i = 0; i < MaxRecentFiles; ++i) {
        recentFileActs[i] = new QAction(this);
        recentFileActs[i]->setVisible(false);
        connect(recentFileActs[i], SIGNAL(triggered()),
                this, SLOT(openRecentFile()));
    }
    exitAct = new QAction(tr("E&xit"), this);
    exitAct->setShortcut(tr("Ctrl+Q"));
    exitAct->setStatusTip(tr("Exit the application"));
    connect(exitAct, SIGNAL(triggered()), qApp, SLOT(closeAllWindows()));
    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()));
}
void MainWindow::createMenus()
{
    fileMenu = menuBar()->addMenu(tr("&File"));
    fileMenu->addAction(newAct);
    fileMenu->addAction(openAct);
    fileMenu->addAction(saveAct);
    fileMenu->addAction(saveAsAct);
    separatorAct = fileMenu->addSeparator();
    for (int i = 0; i < MaxRecentFiles; ++i)
        fileMenu->addAction(recentFileActs[i]);
    fileMenu->addSeparator();
    fileMenu->addAction(exitAct);
    updateRecentFileActions();
    menuBar()->addSeparator();
    helpMenu = menuBar()->addMenu(tr("&Help"));
    helpMenu->addAction(aboutAct);
    helpMenu->addAction(aboutQtAct);
}
void MainWindow::loadFile(const QString &fileName)
{
    QFile file(fileName);
    if (!file.open(QFile::ReadOnly | QFile::Text)) {
        QMessageBox::warning(this, tr("Recent Files"),
                             tr("Cannot read file %1:\n%2.")
                             .arg(fileName)
                             .arg(file.errorString()));
        return;
    }
    QTextStream in(&file);
    QApplication::setOverrideCursor(Qt::WaitCursor);
    textEdit->setPlainText(in.readAll());
    QApplication::restoreOverrideCursor();
    setCurrentFile(fileName);
    statusBar()->showMessage(tr("File loaded"), 2000);
}
void MainWindow::saveFile(const QString &fileName)
{
    QFile file(fileName);
    if (!file.open(QFile::WriteOnly | QFile::Text)) {
        QMessageBox::warning(this, tr("Recent Files"),
                             tr("Cannot write file %1:\n%2.")
                             .arg(fileName)
                             .arg(file.errorString()));
        return;
    }
    QTextStream out(&file);
    QApplication::setOverrideCursor(Qt::WaitCursor);
    out << textEdit->toPlainText();
    QApplication::restoreOverrideCursor();
    setCurrentFile(fileName);
    statusBar()->showMessage(tr("File saved"), 2000);
}
void MainWindow::setCurrentFile(const QString &fileName)
{
    curFile = fileName;
    if (curFile.isEmpty())
        setWindowTitle(tr("Recent Files"));
    else
        setWindowTitle(tr("%1 - %2").arg(strippedName(curFile))
                                    .arg(tr("Recent Files")));
    QSettings settings("Trolltech", "Recent Files Example");
    QStringList files = settings.value("recentFileList").toStringList();
    files.removeAll(fileName);
    files.prepend(fileName);
    while (files.size() > MaxRecentFiles)
        files.removeLast();
    settings.setValue("recentFileList", files);
    foreach (QWidget *widget, QApplication::topLevelWidgets()) {
        MainWindow *mainWin = qobject_cast<MainWindow *>(widget);
        if (mainWin)
            mainWin->updateRecentFileActions();
    }
}
void MainWindow::updateRecentFileActions()
{
    QSettings settings("Trolltech", "Recent Files Example");
    QStringList files = settings.value("recentFileList").toStringList();
    int numRecentFiles = qMin(files.size(), (int)MaxRecentFiles);
    for (int i = 0; i < numRecentFiles; ++i) {
        QString text = tr("&%1 %2").arg(i + 1).arg(strippedName(files[i]));
        recentFileActs[i]->setText(text);
        recentFileActs[i]->setData(files[i]);
        recentFileActs[i]->setVisible(true);
    }
    for (int j = numRecentFiles; j < MaxRecentFiles; ++j)
        recentFileActs[j]->setVisible(false);
    separatorAct->setVisible(numRecentFiles > 0);
}
QString MainWindow::strippedName(const QString &fullFileName)
{
    return QFileInfo(fullFileName).fileName();
}

#include <QApplication>
#include "mainwindow.h"
int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    MainWindow *mainWin = new MainWindow;
    mainWin->show();
    return app.exec();
}