[PATCH] d2d1: Fix uninitialized points[0] in degenerate-radius arc fallback.

[Giang Nguyen]

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 <[e-mail]>
---
 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