QSizeploicy、 QLayout-setSizeConstrain
http://www.tuicool.com/articles/uyaYn2
http://blog.163.com/ojb_123/blog/static/24177424201292805426965/
http://www.tuicool.com/articles/uyaYn2
http://blog.163.com/ojb_123/blog/static/24177424201292805426965/