If a cosmetic polyline contained a 1-pixel segment, the next segment
would be drawn with wrong starting point.
The original fix for QTBUG-26156 had some unwanted side effects
(QTBUG-31579 and now QTBUG-42398). It tried to skip start-point update
if stroke() did not actually draw anything (because the segment was
too small). However, to determine that, it tested for a change in
lastPixel. But that was not failsafe; in some cases (1-pixel segment),
lastPixel could be unchanged even though the segment had been
drawn. With this change, we instead test directly whether stroke()
skipped the segment or not.
Task-number: QTBUG-42398
Change-Id: Id751db69a18cd1af4f45070db9d5698aa532d22a
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@theqtcompany.com>
d5c6335ff3