scrollbar is not working

[chgitcrazy]

When I drag A towards right and down ,I can view the whole graph by right and bottom scroll bar as follows:

But when I drag B towards left and upper , I can't view the whole graph even the scroll bar disappear as follows :

I have set the 'overflow:auto' style in the graph container. So , I can't fix this case and need some help.

[chgitcrazy]

solved