void paint(Canvas canvas, Offset offset)

Paints the text onto the given canvas at the given offset.

Valid only after layout has been called.

Source 

void paint(Canvas canvas, Offset offset) {
  assert(() {
    if (_needsLayout) {
      throw new FlutterError(
        'TextPainter.paint called when text geometry was not yet calculated.\n'
        'Please call layout() before paint() to position the text before painting it.'
      );
    }
    return true;
  });
  canvas.drawParagraph(_paragraph, offset);
}