mainwindow.cpp Example File

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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."));
 }