- Qt 5.5
- Qt Widgets
- Undo Framework Example
- mainwindow.cpp Example File
- Qt 5.5.1 Reference Documentation

# mainwindow.cpp Example File

tools/undoframework/mainwindow.cpp

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    #include <QtWidgets>

    #include "mainwindow.h"
    #include "diagramscene.h"
    #include "diagramitem.h"
    #include "commands.h"

    MainWindow::MainWindow()
    {
        undoStack = new QUndoStack(this);

        createActions();
        createMenus();

        createUndoView();

        diagramScene = new DiagramScene();
        QBrush pixmapBrush(QPixmap(":/images/cross.png").scaled(30, 30));
        diagramScene->setBackgroundBrush(pixmapBrush);
        diagramScene->setSceneRect(QRect(0, 0, 500, 500));

        connect(diagramScene, SIGNAL(itemMoved(DiagramItem*,QPointF)),
                this, SLOT(itemMoved(DiagramItem*,QPointF)));

        setWindowTitle("Undo Framework");
        QGraphicsView *view = new QGraphicsView(diagramScene);
        setCentralWidget(view);
        resize(700, 500);
    }

    void MainWindow::createUndoView()
    {
        undoView = new QUndoView(undoStack);
        undoView->setWindowTitle(tr("Command List"));
        undoView->show();
        undoView->setAttribute(Qt::WA_QuitOnClose, false);
    }

    void MainWindow::createActions()
    {
        deleteAction = new QAction(tr("&Delete Item"), this);
        deleteAction->setShortcut(tr("Del"));
        connect(deleteAction, SIGNAL(triggered()), this, SLOT(deleteItem()));

        addBoxAction = new QAction(tr("Add &Box"), this);
        addBoxAction->setShortcut(tr("Ctrl+O"));
        connect(addBoxAction, SIGNAL(triggered()), this, SLOT(addBox()));

        addTriangleAction = new QAction(tr("Add &Triangle"), this);
        addTriangleAction->setShortcut(tr("Ctrl+T"));
        connect(addTriangleAction, SIGNAL(triggered()), this, SLOT(addTriangle()));

        undoAction = undoStack->createUndoAction(this, tr("&Undo"));
        undoAction->setShortcuts(QKeySequence::Undo);

        redoAction = undoStack->createRedoAction(this, tr("&Redo"));
        redoAction->setShortcuts(QKeySequence::Redo);

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

        aboutAction = new QAction(tr("&About"), this);
        QList<QKeySequence> aboutShortcuts;
        aboutShortcuts << tr("Ctrl+A") << tr("Ctrl+B");
        aboutAction->setShortcuts(aboutShortcuts);
        connect(aboutAction, SIGNAL(triggered()), this, SLOT(about()));
    }

    void MainWindow::createMenus()
    {
        fileMenu = menuBar()->addMenu(tr("&File"));
        fileMenu->addAction(exitAction);

        editMenu = menuBar()->addMenu(tr("&Edit"));
        editMenu->addAction(undoAction);
        editMenu->addAction(redoAction);
        editMenu->addSeparator();
        editMenu->addAction(deleteAction);
        connect(editMenu, SIGNAL(aboutToShow()),
                this, SLOT(itemMenuAboutToShow()));
        connect(editMenu, SIGNAL(aboutToHide()),
                this, SLOT(itemMenuAboutToHide()));

        itemMenu = menuBar()->addMenu(tr("&Item"));
        itemMenu->addAction(addBoxAction);
        itemMenu->addAction(addTriangleAction);

        helpMenu = menuBar()->addMenu(tr("&About"));
        helpMenu->addAction(aboutAction);
    }

    void MainWindow::itemMoved(DiagramItem *movedItem,
                               const QPointF &oldPosition)
    {
        undoStack->push(new MoveCommand(movedItem, oldPosition));
    }

    void MainWindow::deleteItem()
    {
        if (diagramScene->selectedItems().isEmpty())
            return;

        QUndoCommand *deleteCommand = new DeleteCommand(diagramScene);
        undoStack->push(deleteCommand);
    }

    void MainWindow::itemMenuAboutToHide()
    {
        deleteAction->setEnabled(true);
    }

    void MainWindow::itemMenuAboutToShow()
    {
        deleteAction->setEnabled(!diagramScene->selectedItems().isEmpty());
    }

    void MainWindow::addBox()
    {
        QUndoCommand *addCommand = new AddCommand(DiagramItem::Box, diagramScene);
        undoStack->push(addCommand);
    }

    void MainWindow::addTriangle()
    {
        QUndoCommand *addCommand = new AddCommand(DiagramItem::Triangle,
                                                  diagramScene);
        undoStack->push(addCommand);
    }

    void MainWindow::about()
    {
        QMessageBox::about(this, tr("About Undo"),
                           tr("The <b>Undo</b> example demonstrates how to "
                              "use Qt's undo framework."));
    }