gdiplus: Fix GdipFlattenPath for already-flat paths and add a test.

dlls/gdiplus/graphicspath.c

@@ -984,17 +984,16 @@ GpStatus WINGDIPAPI GdipFlattenPath(GpPath *path, GpMatrix* matrix, REAL flatnes
 
         /* always add line points and start points */
         if((type == PathPointTypeStart) || (type == PathPointTypeLine)){
-            type = (path->pathdata.Types[i] & ~PathPointTypeBezier) | PathPointTypeLine;
-            if(!add_path_list_node(node, pt.X, pt.Y, type))
+            if(!add_path_list_node(node, pt.X, pt.Y, path->pathdata.Types[i]))
                 goto memout;
 
             node = node->next;
+            ++i;
             continue;
         }
 
         /* Bezier curve always stored as 4 points */
         if((path->pathdata.Types[i-1] & PathPointTypePathTypeMask) != PathPointTypeStart){
-            type = (path->pathdata.Types[i] & ~PathPointTypeBezier) | PathPointTypeLine;
             if(!add_path_list_node(node, pt.X, pt.Y, type))
                 goto memout;
 

dlls/gdiplus/tests/graphicspath.c

@@ -914,6 +914,11 @@ static path_test_t flattenellipse_path[] = {
     {100.0,25.0, PathPointTypeLine | PathPointTypeCloseSubpath,  0, 1}  /*24*/
     };
 
+static path_test_t flattenline_path[] = {
+    {5.0, 10.0,PathPointTypeStart, 0, 0}, /*0*/
+    {50.0, 100.0, PathPointTypeLine,  0, 0} /*1*/
+    };
+
 static path_test_t flattenarc_path[] = {
     {100.0, 25.0,PathPointTypeStart, 0, 0}, /*0*/
     {99.0, 30.0, PathPointTypeLine,  0, 0}, /*1*/
@@ -966,6 +971,14 @@ static void test_flatten(void)
 
     status = GdipResetPath(path);
     expect(Ok, status);
+    status = GdipAddPathLine(path, 5.0, 10.0, 50.0, 100.0);
+    expect(Ok, status);
+    status = GdipFlattenPath(path, NULL, 1.0);
+    expect(Ok, status);
+    ok_path(path, flattenline_path, sizeof(flattenline_path)/sizeof(path_test_t), FALSE);
+
+    status = GdipResetPath(path);
+    expect(Ok, status);
     status = GdipAddPathArc(path, 0.0, 0.0, 100.0, 50.0, 0.0, 90.0);
     expect(Ok, status);
     status = GdipFlattenPath(path, NULL, 1.0);