Add regression test for arc winding

While the bug has been fixes, the winding handling in the
SetArcGeometry() function isn't tested. This adds a regression
test on EDA_SHAPE, which is where the logic now lives.

Relates-To: https://gitlab.com/kicad/code/kicad/-/issues/15694
Cherry-Pick: fb12db5f2c

qa/unittests/common/test_eda_shape.cpp

@@ -82,7 +82,7 @@ BOOST_AUTO_TEST_CASE( SetAngleAndEnd )
 
         BOOST_CHECK_EQUAL( shape.EndsSwapped(), c.m_ExpectedStartEndSwapped );
 
-        VECTOR2I newEnd = shape.EndsSwapped() ? shape.GetStart() : shape.GetEnd();
+        const VECTOR2I newEnd = shape.EndsSwapped() ? shape.GetStart() : shape.GetEnd();
 
         BOOST_CHECK_PREDICATE(
                 KI_TEST::IsVecWithinTol<VECTOR2I>,
@@ -91,4 +91,87 @@ BOOST_AUTO_TEST_CASE( SetAngleAndEnd )
 }
 
 
+struct SET_ARC_GEOMETRY_CASE
+{
+    std::string m_CaseName;
+    VECTOR2I    m_Start;
+    VECTOR2I    m_Mid;
+    VECTOR2I    m_End;
+    VECTOR2I    m_ExpectedCenter;
+    int         m_ExpectedRadius;
+    bool        m_ExpectedStartEndSwapped;
+    VECTOR2I    m_ExpectedEndAfterSwap;
+    double      m_ExpectedAngleAfterSwapDeg;
+};
+
+static const std::vector<SET_ARC_GEOMETRY_CASE> set_arc_geometry_cases = {
+    {
+            // Test that when setting an arc by start/mid/end, the winding
+            // direction is correctly determined (in 15694, this was in FP_SHAPE,
+            // but the logic has since been merged with EDA_SHAPE).
+            "Issue 15694: clockwise arc",
+            { 10000000, 0 },
+            { 0, 10000000 },
+            { -10000000, 0 },
+            { 0, 0 },
+            10000000,
+            false,
+            { -10000000, 0 }, // unchanged
+            180.0,
+    },
+    {
+            "Issue 15694: anticlockwise arc",
+            { -10000000, 0 },
+            { 0, 10000000 },
+            { 10000000, 0 },
+            { 0, 0 },
+            10000000,
+            true,
+            { 10000000, 0 }, // the start is the end after swapping
+            180.0,           // angle is positive after swapping
+    },
+};
+
+BOOST_AUTO_TEST_CASE( SetArcGeometry )
+{
+    const double angle_tol = 0.1;
+
+    for( const auto& c : set_arc_geometry_cases )
+    {
+        BOOST_TEST_INFO_SCOPE( c.m_CaseName );
+
+        EDA_SHAPE_MOCK shape( SHAPE_T::ARC );
+
+        shape.SetArcGeometry( c.m_Start, c.m_Mid, c.m_End );
+
+        const VECTOR2I center = shape.getCenter();
+
+        BOOST_CHECK_PREDICATE(
+                KI_TEST::IsVecWithinTol<VECTOR2I>,
+                (center) ( c.m_ExpectedCenter ) ( SHAPE_ARC::DefaultAccuracyForPCB() ) );
+
+        const int radius = shape.GetRadius();
+
+        BOOST_CHECK_PREDICATE(
+                KI_TEST::IsWithin<int>,
+                (radius) ( c.m_ExpectedRadius ) ( SHAPE_ARC::DefaultAccuracyForPCB() ) );
+
+        BOOST_CHECK_EQUAL( shape.EndsSwapped(), c.m_ExpectedStartEndSwapped );
+
+        const VECTOR2I newEnd = shape.EndsSwapped() ? shape.GetStart() : shape.GetEnd();
+
+        BOOST_CHECK_PREDICATE(
+                KI_TEST::IsVecWithinTol<VECTOR2I>,
+                (newEnd) ( c.m_ExpectedEndAfterSwap ) ( SHAPE_ARC::DefaultAccuracyForPCB() ) );
+
+        const EDA_ANGLE angle = shape.GetArcAngle();
+
+        BOOST_CHECK_PREDICATE(
+                KI_TEST::IsWithinWrapped<double>,
+                ( angle.AsDegrees() )( c.m_ExpectedAngleAfterSwapDeg )( 360.0 )( angle_tol ) );
+
+        // Check that the centre is still correct
+    }
+}
+
 BOOST_AUTO_TEST_SUITE_END()