mainwindow.cpp Example File

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

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

  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, &MainWindow::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;

      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::getInt(this, tr("Plug & Paint"),
                                                tr("Select brush width:"),
                                                paintArea->brushWidth(),
                                                1, 50, 1, &ok);
      if (ok)
          paintArea->setBrushWidth(newWidth);
  }

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

      paintArea->setBrush(iBrush, brush);
  }

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

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

  void MainWindow::applyFilter()
  {
      auto action = qobject_cast<QAction *>(sender());
      auto 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->setShortcuts(QKeySequence::Open);
      connect(openAct, &QAction::triggered, this, &MainWindow::open);

      saveAsAct = new QAction(tr("&Save As..."), this);
      saveAsAct->setShortcuts(QKeySequence::SaveAs);
      connect(saveAsAct, &QAction::triggered, this, &MainWindow::saveAs);

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

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

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

      brushActionGroup = new QActionGroup(this);

      aboutAct = new QAction(tr("&About"), this);
      connect(aboutAct, &QAction::triggered, this, &MainWindow::about);

      aboutQtAct = new QAction(tr("About &Qt"), this);
      connect(aboutQtAct, &QAction::triggered, qApp, &QApplication::aboutQt);

      aboutPluginsAct = new QAction(tr("About &Plugins"), this);
      connect(aboutPluginsAct, &QAction::triggered, this, &MainWindow::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()
  {
      const auto staticInstances = QPluginLoader::staticInstances();
      for (QObject *plugin : 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");

      const auto entryList = pluginsDir.entryList(QDir::Files);
      for (const QString &fileName : entryList) {
          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)
  {
      auto iBrush = qobject_cast<BrushInterface *>(plugin);
      if (iBrush)
          addToMenu(plugin, iBrush->brushes(), brushMenu, &MainWindow::changeBrush,
                    brushActionGroup);

      auto iShape = qobject_cast<ShapeInterface *>(plugin);
      if (iShape)
          addToMenu(plugin, iShape->shapes(), shapesMenu, &MainWindow::insertShape);

      auto iFilter = qobject_cast<FilterInterface *>(plugin);
      if (iFilter)
          addToMenu(plugin, iFilter->filters(), filterMenu, &MainWindow::applyFilter);
  }

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

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