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."));
  }