d3dx8: Implement D3DXVec2Subtract with a test.

dlls/d3dx8/tests/math.c

@@ -87,6 +87,16 @@ static void D3X8Vector2Test(void)
     got = D3DXVec2LengthSq(NULL);
     ok(fabs( got - expected ) < admitted_error, "Expected: %f, Got: %f\n", expected, got);
 
+/*_______________D3DXVec2Subtract__________________________*/
+   expectedvec.x = 10.0f; expectedvec.y = -5.0f;
+   D3DXVec2Subtract(&gotvec,&u,&v);
+   expect_vec(expectedvec,gotvec);
+   /* Tests the case NULL */
+    funcpointer = D3DXVec2Subtract(&gotvec,NULL,&v);
+    ok(funcpointer == NULL, "Expected: %p, Got: %p\n", NULL, funcpointer);
+    funcpointer = D3DXVec2Subtract(NULL,NULL,NULL);
+    ok(funcpointer == NULL, "Expected: %p, Got: %p\n", NULL, funcpointer);
+
 }
 
 START_TEST(math)

include/d3dx8math.h

@@ -63,5 +63,6 @@ FLOAT D3DXVec2CCW(CONST D3DXVECTOR2 *pv1, CONST D3DXVECTOR2 *pv2);
 FLOAT D3DXVec2Dot(CONST D3DXVECTOR2 *pv1, CONST D3DXVECTOR2 *pv2);
 FLOAT D3DXVec2Length(CONST D3DXVECTOR2 *pv);
 FLOAT D3DXVec2LengthSq(CONST D3DXVECTOR2 *pv);
+D3DXVECTOR2* D3DXVec2Subtract(D3DXVECTOR2 *pout, CONST D3DXVECTOR2 *pv1, CONST D3DXVECTOR2 *pv2);
 
 #endif /* __D3DX8MATH_H__ */

include/d3dx8math.inl

@@ -51,4 +51,12 @@ extern inline FLOAT D3DXVec2LengthSq(CONST D3DXVECTOR2 *pv)
     return( (pv->x) * (pv->x) + (pv->y) * (pv->y) );
 }
 
+extern inline D3DXVECTOR2* D3DXVec2Subtract(D3DXVECTOR2 *pout, CONST D3DXVECTOR2 *pv1, CONST D3DXVECTOR2 *pv2)
+{
+    if ( !pout || !pv1 || !pv2) return NULL;
+    pout->x = pv1->x - pv2->x;
+    pout->y = pv1->y - pv2->y;
+    return pout;
+}
+
 #endif