The GIMP - CPP and G++

[ArbolOne]

Sorry folks, I know this is not the right place to ask this question,
but I would like to rely on your experience and exposure to different
programming techniques to resolve this issue.
I was looking at The GIMP (http://www.gimp.org/screenshots/) specially
the MS-Windows screen-shots, I like the way The GIMP uses a tall side-
window (Pallet) to hold the different tools that might be used, tools
like "Rectangle Select Tool" or "Scissors Select Tool". I would like
to adopt this style for a program I am working on; which also requires
a pallet to hold a number of button or clickable widgets. Does anyone
know of a library that I could use to achieve this purpose? I would
give preference to a GNU library or from the the Free Software
Foundation.

Thanks in advance.