d3dx8: Implement D3DXVec2Lerp with a test.

dlls/d3dx8/tests/math.c

@@ -88,6 +88,16 @@ static void D3X8Vector2Test(void)
     got = D3DXVec2LengthSq(NULL);
     ok(fabs( got - expected ) < admitted_error, "Expected: %f, Got: %f\n", expected, got);
 
+/*_______________D3DXVec2Lerp__________________________*/
+   expectedvec.x = 68.0f; expectedvec.y = -28.5f;
+   D3DXVec2Lerp(&gotvec,&u,&v,scale);
+   expect_vec(expectedvec,gotvec);
+   /* Tests the case NULL */
+    funcpointer = D3DXVec2Lerp(&gotvec,NULL,&v,scale);
+    ok(funcpointer == NULL, "Expected: %p, Got: %p\n", NULL, funcpointer);
+    funcpointer = D3DXVec2Lerp(NULL,NULL,NULL,scale);
+    ok(funcpointer == NULL, "Expected: %p, Got: %p\n", NULL, funcpointer);
+
 /*_______________D3DXVec2Maximize__________________________*/
    expectedvec.x = 3.0f; expectedvec.y = 9.0f;
    D3DXVec2Maximize(&gotvec,&u,&v);

include/d3dx8math.h

@@ -63,6 +63,7 @@ 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* D3DXVec2Lerp(D3DXVECTOR2 *pout, CONST D3DXVECTOR2 *pv1, CONST D3DXVECTOR2 *pv2, FLOAT s);
 D3DXVECTOR2* D3DXVec2Maximize(D3DXVECTOR2 *pout, CONST D3DXVECTOR2 *pv1, CONST D3DXVECTOR2 *pv2);
 D3DXVECTOR2* D3DXVec2Minimize(D3DXVECTOR2 *pout, CONST D3DXVECTOR2 *pv1, CONST D3DXVECTOR2 *pv2);
 D3DXVECTOR2* D3DXVec2Scale(D3DXVECTOR2 *pout, CONST D3DXVECTOR2 *pv, FLOAT s);

include/d3dx8math.inl

@@ -51,6 +51,14 @@ extern inline FLOAT D3DXVec2LengthSq(CONST D3DXVECTOR2 *pv)
     return( (pv->x) * (pv->x) + (pv->y) * (pv->y) );
 }
 
+extern inline D3DXVECTOR2* D3DXVec2Lerp(D3DXVECTOR2 *pout, CONST D3DXVECTOR2 *pv1, CONST D3DXVECTOR2 *pv2, FLOAT s)
+{
+    if ( !pout || !pv1 || !pv2) return NULL;
+    pout->x = (1-s) * (pv1->x) + s * (pv2->x);
+    pout->y = (1-s) * (pv1->y) + s * (pv2->y);
+    return pout;
+}
+
 extern inline D3DXVECTOR2* D3DXVec2Maximize(D3DXVECTOR2 *pout, CONST D3DXVECTOR2 *pv1, CONST D3DXVECTOR2 *pv2)
 {
     if ( !pout || !pv1 || !pv2) return NULL;
@@ -66,6 +74,7 @@ extern inline D3DXVECTOR2* D3DXVec2Minimize(D3DXVECTOR2 *pout, CONST D3DXVECTOR2
     pout->y = min(pv1->y , pv2->y);
     return pout;
 }
+
 extern inline D3DXVECTOR2* D3DXVec2Scale(D3DXVECTOR2 *pout, CONST D3DXVECTOR2 *pv, FLOAT s)
 {
     if ( !pout || !pv) return NULL;