Esme Povirk (@madewokherd) commented about dlls/gdiplus/graphicspath.c:
tmp_points[num_tmp_points].Y = path->pathdata.Points[i].Y + segment_dy * segment_pos / segment_length; widen_open_figure(tmp_points, 0, num_tmp_points, pen, pen_width,
draw_start_cap ? pen->startcap : LineCapFlat,
LineCapFlat, last_point);
draw_start_cap ? pen->startcap : LineCapFlat, pen->customstart,
LineCapFlat, pen->customend, last_point);
It doesn't seem right to pass in non-NULL if we're hard-coding the end cap to Flat.