在递归函数里面用clipPath裁剪

[qinken547]

代码如下：

void draw_tree(htree_node<BoostPolygon2Wm5>* some, unsigned recurs_level,SkCanvas* canvas)  
{
	canvas->save(SkCanvas::kClip_SaveFlag);
	BoostPolygon2Wm5 bPoly = some->name;
	vector<BoostPolygon2Wm5::Wm5Point> pt = bPoly.GetVectorPoints();
	SkPoint * pPoint = new SkPoint[pt.size()];
	for ( int i = 0; i < pt.size() ; i++ )
	{
		pPoint[i] = SkPoint::Make(pt[i].X(),pt[i].Y());
	}
	SkPath path;
	SkPaint paint;
	path.addPoly(pPoint,pt.size(),true);
	paint.setStyle(SkPaint::kStroke_Style);
	paint.setColor(SK_ColorRED);
	paint.setAntiAlias(true);
	if (recurs_level%2)
	{
		canvas->clipPath(path);
	}
	else
	{
		canvas->clipPath(path,SkRegion::kDifference_Op);
	}  
	canvas->drawPath(path,paint);
	canvas->restore();
	delete pPoint;
	
	for (unsigned i = 0; i < some->children.size(); i++)  
		draw_tree(some->children[i], recurs_level+1,canvas);

}  

想实现效果就是每隔一层裁剪一片空白区域
大致可如图

红色是需要裁剪成空白的区域，但现在裁剪出效果却是最大矩形的蓝色，中间的没有效果，是不是我save和restore用错位置了?