LibWeb: Correct SVG smooth curve reflected control point calculation

We were calculating the reflected control points in the svg smooth
curve instructions incorrectly, and this issue was masked by the fact
that we were treating it as a relative coordinate in relative mode.

1 files changed, 6 insertions, 3 deletions

diff --git a/Userland/Libraries/LibWeb/SVG/SVGPathElement.cpp b/Userland/Libraries/LibWeb/SVG/SVGPathElement.cpp
index 3b3e5cd362..b7a8effc18 100644
--- a/Userland/Libraries/LibWeb/SVG/SVGPathElement.cpp
+++ b/Userland/Libraries/LibWeb/SVG/SVGPathElement.cpp
@@ -237,14 +237,17 @@ Gfx::Path& SVGPathElement::get_path()
                 m_previous_control_point = last_point;
             }
 
-            auto reflected_previous_control_x = last_point.dx_relative_to(m_previous_control_point);
-            auto reflected_previous_control_y = last_point.dy_relative_to(m_previous_control_point);
+            // 9.5.2. Reflected control points https://svgwg.org/svg2-draft/paths.html#ReflectedControlPoints
+            // If the current point is (curx, cury) and the final control point of the previous path segment is (oldx2, oldy2),
+            // then the reflected point (i.e., (newx1, newy1), the first control point of the current path segment) is:
+            // (newx1, newy1) = (curx - (oldx2 - curx), cury - (oldy2 - cury))
+            auto reflected_previous_control_x = last_point.x() - m_previous_control_point.dx_relative_to(last_point);
+            auto reflected_previous_control_y = last_point.y() - m_previous_control_point.dy_relative_to(last_point);
             Gfx::FloatPoint c1 = Gfx::FloatPoint { reflected_previous_control_x, reflected_previous_control_y };
             Gfx::FloatPoint c2 = { data[0], data[1] };
             Gfx::FloatPoint p2 = { data[2], data[3] };
             if (!absolute) {
                 p2 += last_point;
-                c1 += last_point;
                 c2 += last_point;
             }
             path.cubic_bezier_curve_to(c1, c2, p2);