Plug & Paint Example | Qt Widgets 5.13.0

Qt 5.13 | Qt Widgets | Plug & Paint Example

Qt 5.13.0 Reference Documentation

# Plug & Paint Example

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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);
              }
          }
      }