jQuery Grid Plugin - jqGrid

I am using jqgrid with jqueryui resizable(the right line is the resize handle)

as you can see in the picture, i gave 50px of scrollOffset.

It works fine at first time… but when I use setGridWidth(both.. using jqueryui resizable and not using) to

resize the grid… It changes into the second grid..

For example if the getGridParam('width') 's value is 100 

and I use setGridWidth(100) by debug console, 

the grid's layout changes into the second picture.. 

I believe this is a bug of jqgrid

Is there anyway to figure this out?

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