Thanks for the advice.
I have seen that when sidebar panel is collapsed, grid’s div is resized in a right way but columns area keep the original size, so it leaves an white area in the right side of the grid (you can see in the second image of my first post).
I have added a button that trigger autoresizecolumns method in grid and it makes it right.
So i think i have to add this method in click event of toogle sidebar button.
Anyway ¿is there any event for grid resizing?
Thanks in advance.