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# mainwindow.cpp Example File
tools/plugandpaint/mainwindow.cpp

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     #include "interfaces.h"
     #include "mainwindow.h"
     #include "paintarea.h"
     #include "plugindialog.h"

     #include <QPluginLoader>
     #include <QTimer>

     #include <QScrollArea>
     #include <QMessageBox>
     #include <QActionGroup>
     #include <QAction>
     #include <QMenu>
     #include <QMenuBar>
     #include <QFileDialog>
     #include <QColorDialog>
     #include <QInputDialog>
     #include <QApplication>

     MainWindow::MainWindow() :
         paintArea(new PaintArea),
         scrollArea(new QScrollArea)
     {
         scrollArea->setBackgroundRole(QPalette::Dark);
         scrollArea->setWidget(paintArea);
         setCentralWidget(scrollArea);

         createActions();
         createMenus();
         loadPlugins();

         setWindowTitle(tr("Plug & Paint"));

         if (!brushActionGroup->actions().isEmpty())
             brushActionGroup->actions().first()->trigger();

         QTimer::singleShot(500, this, SLOT(aboutPlugins()));
     }

     void MainWindow::open()
     {
         const QString fileName = QFileDialog::getOpenFileName(this,
                                                               tr("Open File"),
                                                               QDir::currentPath());
         if (!fileName.isEmpty()) {
             if (!paintArea->openImage(fileName)) {
                 QMessageBox::information(this, tr("Plug & Paint"),
                                          tr("Cannot load %1.").arg(fileName));
                 return;
             }
             paintArea->adjustSize();
         }
     }

     bool MainWindow::saveAs()
     {
         const QString initialPath = QDir::currentPath() + "/untitled.png";

         const QString fileName = QFileDialog::getSaveFileName(this, tr("Save As"),
                                                               initialPath);
         if (fileName.isEmpty()) {
             return false;
         } else {
             return paintArea->saveImage(fileName, "png");
         }
     }

     void MainWindow::brushColor()
     {
         const QColor newColor = QColorDialog::getColor(paintArea->brushColor());
         if (newColor.isValid())
             paintArea->setBrushColor(newColor);
     }

     void MainWindow::brushWidth()
     {
         bool ok;
         const int newWidth = QInputDialog::getInteger(this, tr("Plug & Paint"),
                                                       tr("Select brush width:"),
                                                       paintArea->brushWidth(),
                                                       1, 50, 1, &ok);
         if (ok)
             paintArea->setBrushWidth(newWidth);
     }

     void MainWindow::changeBrush()
     {
         QAction *action = qobject_cast<QAction *>(sender());
         BrushInterface *iBrush = qobject_cast<BrushInterface *>(action->parent());
         const QString brush = action->text();

         paintArea->setBrush(iBrush, brush);
     }

     void MainWindow::insertShape()
     {
         QAction *action = qobject_cast<QAction *>(sender());
         ShapeInterface *iShape = qobject_cast<ShapeInterface *>(action->parent());

         const QPainterPath path = iShape->generateShape(action->text(), this);
         if (!path.isEmpty())
             paintArea->insertShape(path);
     }

     void MainWindow::applyFilter()
     {
         QAction *action = qobject_cast<QAction *>(sender());
         FilterInterface *iFilter =
                 qobject_cast<FilterInterface *>(action->parent());

         const QImage image = iFilter->filterImage(action->text(), paintArea->image(),
                                                   this);
         paintArea->setImage(image);
     }

     void MainWindow::about()
     {
        QMessageBox::about(this, tr("About Plug & Paint"),
                 tr("The <b>Plug & Paint</b> example demonstrates how to write Qt "
                    "applications that can be extended through plugins."));
     }

     void MainWindow::aboutPlugins()
     {
         PluginDialog dialog(pluginsDir.path(), pluginFileNames, this);
         dialog.exec();
     }

     void MainWindow::createActions()
     {
         openAct = new QAction(tr("&Open..."), this);
         openAct->setShortcut(tr("Ctrl+O"));
         connect(openAct, SIGNAL(triggered()), this, SLOT(open()));

         saveAsAct = new QAction(tr("&Save As..."), this);
         saveAsAct->setShortcut(tr("Ctrl+S"));
         connect(saveAsAct, SIGNAL(triggered()), this, SLOT(saveAs()));

         exitAct = new QAction(tr("E&xit"), this);
         exitAct->setShortcut(tr("Ctrl+Q"));
         connect(exitAct, SIGNAL(triggered()), this, SLOT(close()));

         brushColorAct = new QAction(tr("&Brush Color..."), this);
         connect(brushColorAct, SIGNAL(triggered()), this, SLOT(brushColor()));

         brushWidthAct = new QAction(tr("&Brush Width..."), this);
         connect(brushWidthAct, SIGNAL(triggered()), this, SLOT(brushWidth()));

         brushActionGroup = new QActionGroup(this);

         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()));

         aboutPluginsAct = new QAction(tr("About &Plugins"), this);
         connect(aboutPluginsAct, SIGNAL(triggered()), this, SLOT(aboutPlugins()));
     }

     void MainWindow::createMenus()
     {
         fileMenu = menuBar()->addMenu(tr("&File"));
         fileMenu->addAction(openAct);
         fileMenu->addAction(saveAsAct);
         fileMenu->addSeparator();
         fileMenu->addAction(exitAct);

         brushMenu = menuBar()->addMenu(tr("&Brush"));
         brushMenu->addAction(brushColorAct);
         brushMenu->addAction(brushWidthAct);
         brushMenu->addSeparator();

         shapesMenu = menuBar()->addMenu(tr("&Shapes"));

         filterMenu = menuBar()->addMenu(tr("&Filter"));

         menuBar()->addSeparator();

         helpMenu = menuBar()->addMenu(tr("&Help"));
         helpMenu->addAction(aboutAct);
         helpMenu->addAction(aboutQtAct);
         helpMenu->addAction(aboutPluginsAct);
     }

     void MainWindow::loadPlugins()
     {
         foreach (QObject *plugin, QPluginLoader::staticInstances())
             populateMenus(plugin);

         pluginsDir = QDir(qApp->applicationDirPath());

     #if defined(Q_OS_WIN)
         if (pluginsDir.dirName().toLower() == "debug" || pluginsDir.dirName().toLower() == "release")
             pluginsDir.cdUp();
     #elif defined(Q_OS_MAC)
         if (pluginsDir.dirName() == "MacOS") {
             pluginsDir.cdUp();
             pluginsDir.cdUp();
             pluginsDir.cdUp();
         }
     #endif
         pluginsDir.cd("plugins");

         foreach (QString fileName, pluginsDir.entryList(QDir::Files)) {
             QPluginLoader loader(pluginsDir.absoluteFilePath(fileName));
             QObject *plugin = loader.instance();
             if (plugin) {
                 populateMenus(plugin);
                 pluginFileNames += fileName;
             }
         }

         brushMenu->setEnabled(!brushActionGroup->actions().isEmpty());
         shapesMenu->setEnabled(!shapesMenu->actions().isEmpty());
         filterMenu->setEnabled(!filterMenu->actions().isEmpty());
     }

     void MainWindow::populateMenus(QObject *plugin)
     {
         BrushInterface *iBrush = qobject_cast<BrushInterface *>(plugin);
         if (iBrush)
             addToMenu(plugin, iBrush->brushes(), brushMenu, SLOT(changeBrush()),
                       brushActionGroup);

         ShapeInterface *iShape = qobject_cast<ShapeInterface *>(plugin);
         if (iShape)
             addToMenu(plugin, iShape->shapes(), shapesMenu, SLOT(insertShape()));

         FilterInterface *iFilter = qobject_cast<FilterInterface *>(plugin);
         if (iFilter)
             addToMenu(plugin, iFilter->filters(), filterMenu, SLOT(applyFilter()));
     }

     void MainWindow::addToMenu(QObject *plugin, const QStringList &texts,
                                QMenu *menu, const char *member,
                                QActionGroup *actionGroup)
     {
         foreach (QString text, texts) {
             QAction *action = new QAction(text, plugin);
             connect(action, SIGNAL(triggered()), this, member);
             menu->addAction(action);

             if (actionGroup) {
                 action->setCheckable(true);
                 actionGroup->addAction(action);
             }
         }
     }