Displaying line numbers on a page has been an often requested feature. These numbers are not part of the document content. A typical application for this feature is medical transcription where line numbering is required. This can be implemented using TX Text Control with little effort.

Windows Forms

In case of Windows Forms, the line numbers are drawn on top of TXTextControl.TextControl class using a graphics drawing object. The challenge here is to calculate the position of the line object in client coordinates. In TX Text Control X15, a new method has been introduced to simplify this calculation. The TXTextControl.TextControl.DocumentToClient method converts the coordinates in twips in relation to the top-left corner of the document to client coordinates.

private void setLineNumbering()
{
    textControl1.Refresh();

    Graphics g = textControl1.CreateGraphics();

    // iterates all lines
    foreach (TXTextControl.Line line in textControl1.Lines)
    {
        // left position of current line minus offset
        // so that the line number is displayed next to the current line
        int left = line.TextBounds.X - LINE_START_OFFSET;
        //top position of the current line
        int top = line.TextBounds.Top;
        //converts the positon of the current line to client coordinates
        Point p = textControl1.DocumentToClient(new Point(left, top));

        PointF pos = new PointF(p.X , p.Y);

        //draws line number to the specified position
        g.DrawString(line.Number.ToString() + ":",
            new Font(textControl1.Font.Name, textControl1.Font.Size),
            LINE_COLOR, pos);
    }
}

The following screenshot shows the rendered line numbers in the left margin area:

WPF

In WPF, the approach is slightly different and another method has to be used. The TXTextControl.WPF.TextControl.PointToDocument method has also been introduced in version X15, which converts a document point in the current TextControl coordinate system to client coordinates. This method is used to calculate the correct position of text blocks containing line numbers. The text blocks are then added to a canvas control that is displayed on top of TXTextControl.WPF.TextControl class.

The DocumentToClient() and PointFromDocument() methods are helpful methods and have various applications when client coordinates have to be calculated.

Download the sample from our GitHub repository.