Initialize the lastDir properly, to avoid the stroking algorithm doing
direction-change handling for a single line. That could cause a cap to
be painted for a single FlatCap line.
Also fixes a bug in tst_qpainter, revealed by the above fix. The
result drawPolyline was erroneously compared to the result of drawing
the lines individually, for a case where the former correctly paints
the pixel of the join point in the corner, while the latter by
coincidence used to paint the same pixel as a cap because of the bug
above.
Task-number: QTBUG-70101
Change-Id: Ie20eda33214cfe9e7627f17ef4c7a5b3835c9c24
Reviewed-by: Lars Knoll <lars.knoll@qt.io>
b233ce66d3