Arrow head size mismatch between ROI editing and rendering

[Rdornier]

When we draw an arrow on an image, especially with a large stroke width, the arrow head appears much larger than the one drawn.
On certain cases, the arrow line is shown as 'negative' on the arrow head.

Figure version when testing: <= 7.2.1

It would be nice if we can have the same rendering on both modal dialog and figure.