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# mainwindow.cpp Example File
demos/undo/mainwindow.cpp

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     #include <QUndoGroup>
     #include <QUndoStack>
     #include <QFileDialog>
     #include <QMessageBox>
     #include <QTextStream>
     #include <QToolButton>
     #include "document.h"
     #include "mainwindow.h"
     #include "commands.h"

     MainWindow::MainWindow(QWidget *parent)
         : QMainWindow(parent)
     {
         setupUi(this);

         QWidget *w = documentTabs->widget(0);
         documentTabs->removeTab(0);
         delete w;

         connect(actionOpen, SIGNAL(triggered()), this, SLOT(openDocument()));
         connect(actionClose, SIGNAL(triggered()), this, SLOT(closeDocument()));
         connect(actionNew, SIGNAL(triggered()), this, SLOT(newDocument()));
         connect(actionSave, SIGNAL(triggered()), this, SLOT(saveDocument()));
         connect(actionExit, SIGNAL(triggered()), this, SLOT(close()));
         connect(actionRed, SIGNAL(triggered()), this, SLOT(setShapeColor()));
         connect(actionGreen, SIGNAL(triggered()), this, SLOT(setShapeColor()));
         connect(actionBlue, SIGNAL(triggered()), this, SLOT(setShapeColor()));
         connect(actionAddCircle, SIGNAL(triggered()), this, SLOT(addShape()));
         connect(actionAddRectangle, SIGNAL(triggered()), this, SLOT(addShape()));
         connect(actionAddTriangle, SIGNAL(triggered()), this, SLOT(addShape()));
         connect(actionRemoveShape, SIGNAL(triggered()), this, SLOT(removeShape()));
         connect(actionAddRobot, SIGNAL(triggered()), this, SLOT(addRobot()));
         connect(actionAddSnowman, SIGNAL(triggered()), this, SLOT(addSnowman()));
         connect(actionAbout, SIGNAL(triggered()), this, SLOT(about()));
         connect(actionAboutQt, SIGNAL(triggered()), this, SLOT(aboutQt()));

         connect(undoLimit, SIGNAL(valueChanged(int)), this, SLOT(updateActions()));
         connect(documentTabs, SIGNAL(currentChanged(int)), this, SLOT(updateActions()));

         actionOpen->setShortcut(QString("Ctrl+O"));
         actionClose->setShortcut(QString("Ctrl+W"));
         actionNew->setShortcut(QString("Ctrl+N"));
         actionSave->setShortcut(QString("Ctrl+S"));
         actionExit->setShortcut(QString("Ctrl+Q"));
         actionRemoveShape->setShortcut(QString("Del"));
         actionRed->setShortcut(QString("Alt+R"));
         actionGreen->setShortcut(QString("Alt+G"));
         actionBlue->setShortcut(QString("Alt+B"));
         actionAddCircle->setShortcut(QString("Alt+C"));
         actionAddRectangle->setShortcut(QString("Alt+L"));
         actionAddTriangle->setShortcut(QString("Alt+T"));

         m_undoGroup = new QUndoGroup(this);
         undoView->setGroup(m_undoGroup);
         undoView->setCleanIcon(QIcon(":/icons/ok.png"));

         QAction *undoAction = m_undoGroup->createUndoAction(this);
         QAction *redoAction = m_undoGroup->createRedoAction(this);
         undoAction->setIcon(QIcon(":/icons/undo.png"));
         redoAction->setIcon(QIcon(":/icons/redo.png"));
         menuShape->insertAction(menuShape->actions().at(0), undoAction);
         menuShape->insertAction(undoAction, redoAction);

         toolBar->addAction(undoAction);
         toolBar->addAction(redoAction);

         newDocument();
         updateActions();
     };

     void MainWindow::updateActions()
     {
         Document *doc = currentDocument();
         m_undoGroup->setActiveStack(doc == 0 ? 0 : doc->undoStack());
         QString shapeName = doc == 0 ? QString() : doc->currentShapeName();

         actionAddRobot->setEnabled(doc != 0);
         actionAddSnowman->setEnabled(doc != 0);
         actionAddCircle->setEnabled(doc != 0);
         actionAddRectangle->setEnabled(doc != 0);
         actionAddTriangle->setEnabled(doc != 0);
         actionClose->setEnabled(doc != 0);
         actionSave->setEnabled(doc != 0 && !doc->undoStack()->isClean());
         undoLimit->setEnabled(doc != 0 && doc->undoStack()->count() == 0);

         if (shapeName.isEmpty()) {
             actionRed->setEnabled(false);
             actionGreen->setEnabled(false);
             actionBlue->setEnabled(false);
             actionRemoveShape->setEnabled(false);
         } else {
             Shape shape = doc->shape(shapeName);
             actionRed->setEnabled(shape.color() != Qt::red);
             actionGreen->setEnabled(shape.color() != Qt::green);
             actionBlue->setEnabled(shape.color() != Qt::blue);
             actionRemoveShape->setEnabled(true);
         }

         if (doc != 0) {
             int index = documentTabs->indexOf(doc);
             Q_ASSERT(index != -1);
             static const QIcon unsavedIcon(":/icons/filesave.png");
             documentTabs->setTabIcon(index, doc->undoStack()->isClean() ? QIcon() : unsavedIcon);

             if (doc->undoStack()->count() == 0)
                 doc->undoStack()->setUndoLimit(undoLimit->value());
         }
     }

     void MainWindow::openDocument()
     {
         QString fileName = QFileDialog::getOpenFileName(this);
         if (fileName.isEmpty())
             return;

         QFile file(fileName);
         if (!file.open(QIODevice::ReadOnly)) {
             QMessageBox::warning(this,
                                 tr("File error"),
                                 tr("Failed to open\n%1").arg(fileName));
             return;
         }
         QTextStream stream(&file);

         Document *doc = new Document();
         if (!doc->load(stream)) {
             QMessageBox::warning(this,
                                 tr("Parse error"),
                                 tr("Failed to parse\n%1").arg(fileName));
             delete doc;
             return;
         }

         doc->setFileName(fileName);
         addDocument(doc);
     }

     QString MainWindow::fixedWindowTitle(const Document *doc) const
     {
         QString title = doc->fileName();

         if (title.isEmpty())
             title = tr("Unnamed");
         else
             title = QFileInfo(title).fileName();

         QString result;

         for (int i = 0; ; ++i) {
             result = title;
             if (i > 0)
                 result += QString::number(i);

             bool unique = true;
             for (int j = 0; j < documentTabs->count(); ++j) {
                 const QWidget *widget = documentTabs->widget(j);
                 if (widget == doc)
                     continue;
                 if (result == documentTabs->tabText(j)) {
                     unique = false;
                     break;
                 }
             }

             if (unique)
                 break;
         }

         return result;
     }

     void MainWindow::addDocument(Document *doc)
     {
         if (documentTabs->indexOf(doc) != -1)
             return;
         m_undoGroup->addStack(doc->undoStack());
         documentTabs->addTab(doc, fixedWindowTitle(doc));
         connect(doc, SIGNAL(currentShapeChanged(QString)), this, SLOT(updateActions()));
         connect(doc->undoStack(), SIGNAL(indexChanged(int)), this, SLOT(updateActions()));
         connect(doc->undoStack(), SIGNAL(cleanChanged(bool)), this, SLOT(updateActions()));

         setCurrentDocument(doc);
     }

     void MainWindow::setCurrentDocument(Document *doc)
     {
         documentTabs->setCurrentWidget(doc);
     }

     Document *MainWindow::currentDocument() const
     {
         return qobject_cast<Document*>(documentTabs->currentWidget());
     }

     void MainWindow::removeDocument(Document *doc)
     {
         int index = documentTabs->indexOf(doc);
         if (index == -1)
             return;

         documentTabs->removeTab(index);
         m_undoGroup->removeStack(doc->undoStack());
         disconnect(doc, SIGNAL(currentShapeChanged(QString)), this, SLOT(updateActions()));
         disconnect(doc->undoStack(), SIGNAL(indexChanged(int)), this, SLOT(updateActions()));
         disconnect(doc->undoStack(), SIGNAL(cleanChanged(bool)), this, SLOT(updateActions()));

         if (documentTabs->count() == 0) {
             newDocument();
             updateActions();
         }
     }

     void MainWindow::saveDocument()
     {
         Document *doc = currentDocument();
         if (doc == 0)
             return;

         for (;;) {
             QString fileName = doc->fileName();

             if (fileName.isEmpty())
                 fileName = QFileDialog::getSaveFileName(this);
             if (fileName.isEmpty())
                 break;

             QFile file(fileName);
             if (!file.open(QIODevice::WriteOnly)) {
                 QMessageBox::warning(this,
                                     tr("File error"),
                                     tr("Failed to open\n%1").arg(fileName));
                 doc->setFileName(QString());
             } else {
                 QTextStream stream(&file);
                 doc->save(stream);
                 doc->setFileName(fileName);

                 int index = documentTabs->indexOf(doc);
                 Q_ASSERT(index != -1);
                 documentTabs->setTabText(index, fixedWindowTitle(doc));

                 break;
             }
         }
     }

     void MainWindow::closeDocument()
     {
         Document *doc = currentDocument();
         if (doc == 0)
             return;

         if (!doc->undoStack()->isClean()) {
             int button
                 = QMessageBox::warning(this,
                                 tr("Unsaved changes"),
                                 tr("Would you like to save this document?"),
                                 QMessageBox::Yes, QMessageBox::No);
             if (button == QMessageBox::Yes)
                 saveDocument();
         }

         removeDocument(doc);
         delete doc;
     }

     void MainWindow::newDocument()
     {
         addDocument(new Document());
     }

     static QColor randomColor()
     {
         int r = (int) (3.0*(rand()/(RAND_MAX + 1.0)));
         switch (r) {
             case 0:
                 return Qt::red;
             case 1:
                 return Qt::green;
             default:
                 break;
         }
         return Qt::blue;
     }

     static QRect randomRect(const QSize &s)
     {
         QSize min = Shape::minSize;

         int left = (int) ((0.0 + s.width() - min.width())*(rand()/(RAND_MAX + 1.0)));
         int top = (int) ((0.0 + s.height() - min.height())*(rand()/(RAND_MAX + 1.0)));
         int width = (int) ((0.0 + s.width() - left - min.width())*(rand()/(RAND_MAX + 1.0))) + min.width();
         int height = (int) ((0.0 + s.height() - top - min.height())*(rand()/(RAND_MAX + 1.0))) + min.height();

         return QRect(left, top, width, height);
     }

     void MainWindow::addShape()
     {
         Document *doc = currentDocument();
         if (doc == 0)
             return;

         Shape::Type type;

         if (sender() == actionAddCircle)
             type = Shape::Circle;
         else if (sender() == actionAddRectangle)
             type = Shape::Rectangle;
         else if (sender() == actionAddTriangle)
             type = Shape::Triangle;
         else return;

         Shape newShape(type, randomColor(), randomRect(doc->size()));
         doc->undoStack()->push(new AddShapeCommand(doc, newShape));
     }

     void MainWindow::removeShape()
     {
         Document *doc = currentDocument();
         if (doc == 0)
             return;

         QString shapeName = doc->currentShapeName();
         if (shapeName.isEmpty())
             return;

         doc->undoStack()->push(new RemoveShapeCommand(doc, shapeName));
     }

     void MainWindow::setShapeColor()
     {
         Document *doc = currentDocument();
         if (doc == 0)
             return;

         QString shapeName = doc->currentShapeName();
         if (shapeName.isEmpty())
             return;

         QColor color;

         if (sender() == actionRed)
             color = Qt::red;
         else if (sender() == actionGreen)
             color = Qt::green;
         else if (sender() == actionBlue)
             color = Qt::blue;
         else
             return;

         if (color == doc->shape(shapeName).color())
             return;

         doc->undoStack()->push(new SetShapeColorCommand(doc, shapeName, color));
     }

     void MainWindow::addSnowman()
     {
         Document *doc = currentDocument();
         if (doc == 0)
             return;

         // Create a macro command using beginMacro() and endMacro()

         doc->undoStack()->beginMacro(tr("Add snowman"));
         doc->undoStack()->push(new AddShapeCommand(doc,
                                 Shape(Shape::Circle, Qt::blue, QRect(51, 30, 97, 95))));
         doc->undoStack()->push(new AddShapeCommand(doc,
                                 Shape(Shape::Circle, Qt::blue, QRect(27, 123, 150, 133))));
         doc->undoStack()->push(new AddShapeCommand(doc,
                                 Shape(Shape::Circle, Qt::blue, QRect(11, 253, 188, 146))));
         doc->undoStack()->endMacro();
     }

     void MainWindow::addRobot()
     {
         Document *doc = currentDocument();
         if (doc == 0)
             return;

         // Compose a macro command by explicitly adding children to a parent command

         QUndoCommand *parent = new QUndoCommand(tr("Add robot"));

         new AddShapeCommand(doc, Shape(Shape::Rectangle, Qt::green, QRect(115, 15, 81, 70)), parent);
         new AddShapeCommand(doc, Shape(Shape::Rectangle, Qt::green, QRect(82, 89, 148, 188)), parent);
         new AddShapeCommand(doc, Shape(Shape::Rectangle, Qt::green, QRect(76, 280, 80, 165)), parent);
         new AddShapeCommand(doc, Shape(Shape::Rectangle, Qt::green, QRect(163, 280, 80, 164)), parent);
         new AddShapeCommand(doc, Shape(Shape::Circle, Qt::blue, QRect(116, 25, 80, 50)), parent);
         new AddShapeCommand(doc, Shape(Shape::Rectangle, Qt::green, QRect(232, 92, 80, 127)), parent);
         new AddShapeCommand(doc, Shape(Shape::Rectangle, Qt::green, QRect(2, 92, 80, 125)), parent);

         doc->undoStack()->push(parent);
     }

     void MainWindow::about()
     {
         QMessageBox::about(this, tr("About Undo"), tr("The Undo demonstration shows how to use the Qt Undo framework."));
     }

     void MainWindow::aboutQt()
     {
         QMessageBox::aboutQt(this, tr("About Qt"));
     }