mainwindow.cpp Example File

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  #include "mainwindow.h"
  #include "previewpage.h"
  #include "ui_mainwindow.h"

  #include <QFile>
  #include <QFileDialog>
  #include <QFontDatabase>
  #include <QMessageBox>
  #include <QTextStream>
  #include <QWebChannel>

  MainWindow::MainWindow(QWidget *parent) :
      QMainWindow(parent),
      ui(new Ui::MainWindow)
  {
      ui->setupUi(this);
      ui->editor->setFont(QFontDatabase::systemFont(QFontDatabase::FixedFont));
      ui->preview->setContextMenuPolicy(Qt::NoContextMenu);

      PreviewPage *page = new PreviewPage(this);
      ui->preview->setPage(page);

      connect(ui->editor, &QPlainTextEdit::textChanged,
              [this]() { m_content.setText(ui->editor->toPlainText()); });

      QWebChannel *channel = new QWebChannel(this);
      channel->registerObject(QStringLiteral("content"), &m_content);
      page->setWebChannel(channel);

      ui->preview->setUrl(QUrl("qrc:/index.html"));

      connect(ui->actionNew, &QAction::triggered, this, &MainWindow::onFileNew);
      connect(ui->actionOpen, &QAction::triggered, this, &MainWindow::onFileOpen);
      connect(ui->actionSave, &QAction::triggered, this, &MainWindow::onFileSave);
      connect(ui->actionSaveAs, &QAction::triggered, this, &MainWindow::onFileSaveAs);
      connect(ui->actionExit, &QAction::triggered, this, &MainWindow::onExit);

      connect(ui->editor->document(), &QTextDocument::modificationChanged,
              ui->actionSave, &QAction::setEnabled);

      QFile defaultTextFile(":/default.md");
      defaultTextFile.open(QIODevice::ReadOnly);
      ui->editor->setPlainText(defaultTextFile.readAll());
  }

  MainWindow::~MainWindow()
  {
      delete ui;
  }

  void MainWindow::openFile(const QString &path)
  {
      QFile f(path);
      if (!f.open(QIODevice::ReadOnly)) {
          QMessageBox::warning(this, windowTitle(),
                               tr("Could not open file %1: %2").arg(
                                   QDir::toNativeSeparators(path), f.errorString()));
          return;
      }
      m_filePath = path;
      ui->editor->setPlainText(f.readAll());
  }

  bool MainWindow::isModified() const
  {
      return ui->editor->document()->isModified();
  }

  void MainWindow::onFileNew()
  {
      if (isModified()) {
          QMessageBox::StandardButton button = QMessageBox::question(this, windowTitle(),
                               tr("You have unsaved changes. Do you want to create a new document anyway?"));
          if (button != QMessageBox::Yes)
              return;
      }

      m_filePath.clear();
      ui->editor->setPlainText(tr("## New document"));
      ui->editor->document()->setModified(false);
  }

  void MainWindow::onFileOpen()
  {
      if (isModified()) {
          QMessageBox::StandardButton button = QMessageBox::question(this, windowTitle(),
                               tr("You have unsaved changes. Do you want to open a new document anyway?"));
          if (button != QMessageBox::Yes)
              return;
      }

      QString path = QFileDialog::getOpenFileName(this,
          tr("Open MarkDown File"), "", tr("MarkDown File (*.md)"));
      if (path.isEmpty())
          return;

      openFile(path);
  }

  void MainWindow::onFileSave()
  {
      if (m_filePath.isEmpty()) {
          onFileSaveAs();
          return;
      }

      QFile f(m_filePath);
      if (!f.open(QIODevice::WriteOnly | QIODevice::Text))  {
          QMessageBox::warning(this, windowTitle(),
                               tr("Could not write to file %1: %2").arg(
                                   QDir::toNativeSeparators(m_filePath), f.errorString()));
          return;
      }
      QTextStream str(&f);
      str << ui->editor->toPlainText();

      ui->editor->document()->setModified(false);
  }

  void MainWindow::onFileSaveAs()
  {
      QString path = QFileDialog::getSaveFileName(this,
          tr("Save MarkDown File"), "", tr("MarkDown File (*.md, *.markdown)"));
      if (path.isEmpty())
          return;
      m_filePath = path;
      onFileSave();
  }

  void MainWindow::onExit()
  {
      if (isModified()) {
          QMessageBox::StandardButton button = QMessageBox::question(this, windowTitle(),
                               tr("You have unsaved changes. Do you want to exit anyway?"));
          if (button != QMessageBox::Yes)
              return;
      }
      close();
  }