For my whats failing is this code, the layout system has nothing to do, as the margins are inside the widget.

(edit: just remembered, parts of this code are based on QDevelop, so they are GPL)

Qt Code: 
  1. #include <QTextEdit>
  2.  
  4.  
  5. class newedit : public QTextEdit
  6. {
  7. Q_OBJECT
  8. public:
  9. 	newedit(QWidget* parent);
  10.  
  11. protected:
  12. 	void paintEvent ( QPaintEvent * event );
  13.  
  14. };
  15.  
  16. #include "newedit.h"
  17. #include <QApplication>
  18. #include <QPainter>
  19. #include <QTextBlock>
  20. #include <QTextLayout>
  21. #include <QScrollBar>
  22.  
  23. newedit::newedit( QWidget* parent ) 
  25. {
  26. 	setViewportMargins( 50, 0, 0, 0 );
  27. }
  28.  
  29. void newedit::paintEvent( QPaintEvent * event )
  30. {
  31. 	QTextEdit::paintEvent( event );
  32.  
  33. 	int contentsY = verticalScrollBar()->value();
  34. 	qreal pageBottom = contentsY + viewport()->height();
  35. 	int m_lineNumber = 1;
  36. 	const QFontMetrics fm = fontMetrics();
  37. 	const int ascent = fontMetrics().ascent() +1;
  38.  
  39. 	QPainter p( this );
  40. 	for ( QTextBlock block = document()->begin(); block.isValid(); block = block.next(), m_lineNumber++ )
  41. 	{
  42. 		QTextLayout* layout = block.layout();
  43. 		const QRectF boundingRect = layout->boundingRect();
  44. 		QPointF position = layout->position();
  45. 		if ( position.y() +boundingRect.height() < contentsY )
  46. 			continue;
  47. 		if ( position.y() > pageBottom )
  48. 			break;
  49.  
  50. 		const QString txt = QString::number( m_lineNumber );
  51.  
  52. 		p.drawText( width() -fm.width( txt ) - 2, qRound( position.y() ) -contentsY +ascent, txt ); // -fm.width( "0" ) is an ampty place/indent 
  53. 	}	
  54.  
  55. }
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