Keeping the left side of a splitter from resizing

[MrGarbage]

Hi,

In the attached example .ui I have used the Designer to
create a left and right groupbox layed out horizontally in a splitter.

I would like the leftmost groupbox to NOT resize when I horizontally
increase the size of the main window. Using the splitter I can and should
be able to increase or decrease the size of the leftmost groupbox. But it
should remain at it's current width when resizing the main window. Only the
rightmost groupbox should resize.

I cannot find the correct layout settings to accomplish this.

Thank you.