When d2d_arc_to_bezier() rejects an arc because both radii are below the fuzz threshold, it returns 0 to signal "treat as a straight line". The caller d2d_figure_add_arc() then passes points[0] to d2d_figure_add_lines() as the line endpoint: count = d2d_arc_to_bezier(&figure->vertices[last], arc, points); if (count > 0) return d2d_figure_add_beziers(figure, ...); else if (count == 0) return d2d_figure_add_lines(figure, points, 1); But points[0] is never written on the radius-rejection path, so add_lines() consumes uninitialized stack memory as the endpoint. Result: random line target, undefined visual behavior for any path that contains a degenerate-radius arc. Fix is to write the arc's specified end point into points[0] before returning 0, which matches the natural fallback semantics ("draw a line from the previous vertex to the arc's endpoint"). Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=59718 Signed-off-by: Giang Nguyen <nen24t@gmail.com> --- dlls/d2d1/geometry.c | 1 + 1 file changed, 1 insertion(+) diff --git a/dlls/d2d1/geometry.c b/dlls/d2d1/geometry.c index 68de4c2193c..51d587673dd 100644 --- a/dlls/d2d1/geometry.c +++ b/dlls/d2d1/geometry.c @@ -1247,6 +1247,7 @@ static int d2d_arc_to_bezier(const D2D_POINT_2F *start_point, const D2D1_ARC_SEG if (!d2d_arc_check_radius(rHalfChord2, fuzz2, &radius.x) || !d2d_arc_check_radius(rHalfChord2, fuzz2, &radius.y)) { + points[0] = arc->point; return 0; } -- 2.43.0