gdi32: Skip scan conversion on overflow.

dlls/gdi32/region.c

@@ -2742,7 +2742,7 @@ HRGN create_polypolygon_region( const POINT *Pts, const INT *Count, INT nbpolygo
     nb_points = REGION_CreateEdgeTable( Count, nbpolygons, Pts, &ET, pETEs, &SLLBlock, clip_rect );
     if ((obj = alloc_region( nb_points / 2 )))
     {
-        scan_convert( obj, &ET, mode, clip_rect );
+        if (nb_points) scan_convert( obj, &ET, mode, clip_rect );
 
         if (!(hrgn = alloc_gdi_handle( obj, OBJ_REGION, &region_funcs )))
             free_region( obj );

dlls/gdi32/tests/clipping.c

@@ -513,8 +513,10 @@ static void test_CreatePolyPolygonRgn(void)
     POINT points_mixed[] = { {0, 0}, {0, 0}, {0, 0}, {6, 6}, {6, 6}, {6, 6} };
     POINT points_six[] = { {6, 6}, {6, 6}, {6, 6} };
     POINT points_line[] = { {1, 0}, {11, 0}, {21, 0}};
+    POINT points_overflow[] = { {0, 0}, {1, 0}, {0, 0x80000000} };
     INT counts_single_poly[] = { 3 };
     INT counts_two_poly[] = { 3, 3 };
+    INT counts_overflow[] = { ARRAY_SIZE(points_overflow) };
     int ret;
     RECT rect;
 
@@ -543,6 +545,13 @@ static void test_CreatePolyPolygonRgn(void)
     ret = GetRgnBox(region, &rect);
     ok (ret == NULLREGION, "Expected NULLREGION, got %d\n", ret);
     DeleteObject(region);
+
+    /* Test with points that overflow the edge table */
+    region = CreatePolyPolygonRgn(points_overflow, counts_overflow, ARRAY_SIZE(counts_overflow), ALTERNATE);
+    ok (region != NULL, "region must not be NULL\n");
+    ret = GetRgnBox(region, &rect);
+    ok (ret == NULLREGION, "Expected NULLREGION, got %d\n", ret);
+    DeleteObject(region);
 }
 
 START_TEST(clipping)