code_viewer.h

#pragma once
 
#include <QPlainTextEdit>
 
class LineNumberArea;
 
class CodeViewer : public QPlainTextEdit
{
  Q_OBJECT
 
public:
  CodeViewer(QWidget* parent = nullptr);
 
  void lineNumberAreaPaintEvent(QPaintEvent* event);
  int lineNumberAreaWidth() const;
 
protected:
  void resizeEvent(QResizeEvent* event) override;
 
private slots:
  void updateLineNumberAreaWidth(int newBlockCount);
  void highlightCurrentLine();
  void updateLineNumberArea(const QRect& rect, int dy);
 
private:
  LineNumberArea* mLineNumberArea = nullptr;
};
 
class LineNumberArea : public QWidget
{
public:
  LineNumberArea(CodeViewer* editor)
      : QWidget(editor)
      , mEditor(editor)
  {
  }
 
  QSize sizeHint() const override
  {
    return QSize(mEditor->lineNumberAreaWidth(), 0);
  }
 
protected:
  void paintEvent(QPaintEvent* event) override
  {
    mEditor->lineNumberAreaPaintEvent(event);
  }
 
private:
  CodeViewer* mEditor = nullptr;
};