webtester/src/editor.hxx

#ifndef EDITOR_HXX
#define EDITOR_HXX
/// from qt http://doc.qt.io/qt-5/qtwidgets-widgets-codeeditor-example.html

#include <QPlainTextEdit>
#include <QPainter>
#include <QTextBlock>
#include <QResizeEvent>

class CodeEditor;

class LineNumberArea: public QWidget {
  public:
    LineNumberArea(CodeEditor *editor);
    QSize sizeHint() const override;
  protected:
    void paintEvent(QPaintEvent *event) override;
  private:
    CodeEditor *codeEditor;
};

class CodeEditor: public QPlainTextEdit {
    Q_OBJECT;
  public:
    CodeEditor(QWidget *parent = 0): QPlainTextEdit(parent) {
      lineNumberArea = new LineNumberArea(this);
      connect(this, SIGNAL(blockCountChanged(int)), this, SLOT(updateLineNumberAreaWidth(int)));
      connect(this, SIGNAL(updateRequest(QRect,int)), this, SLOT(updateLineNumberArea(QRect,int)));
      connect(this, SIGNAL(cursorPositionChanged()), this, SLOT(highlightCurrentLine()));
      updateLineNumberAreaWidth(0);
      highlightCurrentLine();
    }
    void lineNumberAreaPaintEvent(QPaintEvent *event) {
      QPainter painter(lineNumberArea);
      painter.fillRect(event->rect(), Qt::lightGray);
      QTextBlock block = firstVisibleBlock();
      int blockNumber = block.blockNumber();
      int top = (int) blockBoundingGeometry(block).translated(contentOffset()).top();
      int bottom = top + (int) blockBoundingRect(block).height();
      while (block.isValid() && top <= event->rect().bottom()) {
        if (block.isVisible() && bottom >= event->rect().top()) {
          QString number = QString::number(blockNumber + 1);
            painter.setPen(Qt::black);
            painter.drawText(0, top, lineNumberArea->width(), fontMetrics().height(),
                             Qt::AlignRight, number);
        }
        block = block.next();
        top = bottom;
        bottom = top + (int) blockBoundingRect(block).height();
        ++blockNumber;
      }
    }
    int lineNumberAreaWidth() {
      int digits(1);
      int max = qMax(1, blockCount());
      while (max >= 10) {
        max /= 10;
        ++digits;
      }
      int space = 3 + fontMetrics().width(QLatin1Char('9')) * digits;
      return space;
    }
  protected:
    void resizeEvent(QResizeEvent *e) override {
      QPlainTextEdit::resizeEvent(e);
      QRect cr = contentsRect();
      lineNumberArea->setGeometry(QRect(cr.left(), cr.top(), lineNumberAreaWidth(), cr.height()));
    }
  private Q_SLOTS:
    void updateLineNumberAreaWidth(int newBlockCount) {
      setViewportMargins(lineNumberAreaWidth(), 0, 0, 0);
    }
    void highlightCurrentLine() {
      QList<QTextEdit::ExtraSelection> extraSelections;
      if (!isReadOnly()) {
        QTextEdit::ExtraSelection selection;
        QColor lineColor = QColor(Qt::yellow).lighter(160);
        selection.format.setBackground(lineColor);
        selection.format.setProperty(QTextFormat::FullWidthSelection, true);
        selection.cursor = textCursor();
        selection.cursor.clearSelection();
        extraSelections.append(selection);
      }
      setExtraSelections(extraSelections);
    }
    void updateLineNumberArea(const QRect &rect, int dy) {
      if (dy)
        lineNumberArea->scroll(0, dy);
      else
        lineNumberArea->update(0, rect.y(), lineNumberArea->width(), rect.height());
      if (rect.contains(viewport()->rect()))
        updateLineNumberAreaWidth(0);
    }
  private:
    QWidget *lineNumberArea;
};

inline LineNumberArea::LineNumberArea(CodeEditor *editor): QWidget(editor) {
  codeEditor = editor;
}
inline QSize LineNumberArea::sizeHint() const {
  return QSize(codeEditor->lineNumberAreaWidth(), 0);
}
inline void LineNumberArea::paintEvent(QPaintEvent *event) {
  codeEditor->lineNumberAreaPaintEvent(event);
}
#endif