In a GUI system, what would be a good way to represent pop-up items such as menus and dialog boxes?

As to your final question, if you don't use inheritance to push a parent window's screen position to its children, you could push that information through parameters when the parent window makes the function calls to pop-up its child widget(s).

Honestly there are so many already built GUI systems that you are probably wasting your time working on this unless you are just doing it solely to teach yourself something. For Windows you could try, GDI, Win32 APIs, for DirectX you could use DXUT, for other platforms and languages simple Google searches will turn up a few pre-built GUI libraries you could link into your project (Scaleform is a good choice for larger more professional projects).

I could start a new thread on this, but requirements and restrictions prevent me from using most libraries. I want to be cross platform - I'm actually developing on a Mac - so Windows and DirectX based libraries are out (so are Apple's libraries). I'm doing this as a hobby and intend to make my game open source, so it's hard to justify to myself spending money on a GUI library, or even a general toolkit like Flash. Most of the cross platform open source [C++] libraries besides CEGUI seem to be in a perpetually alpha state, and I was turned off by CEGUI because it seemed to want to do its own rendering and resource management independent of my own engine's rendering and resource management. I briefly looked at libRocket and decided structuring everything in HTML didn't mesh with me since I couldn't figure out how to make a mouse cursor. And I'm programming my game in Ruby with Gosu, so most of those libraries would be unusable for me anyway.

Hello,

At Coherent Labs we're developing a HTML5-based GUI library that will help you with the pop-up GUI. However, we're a commercial closed source vendor. So it might not be appropriate for your game but you can give it a try.

There are also some open source solutions that might help you out:

Chromium Embedded Framework

EAWebKit

I hope this will help you out with your project.

Thanks for the post, Martin, though unfortunately I'm not sure your suggestions would be much help.

There are also some open source solutions that might help you out:
Chromium Embedded Framework
EAWebKit

There isn't any info on the EAWebKit page. Just a couple of download links.

The Chromium Embedded Framework would require me to dip into C++. In that case I'd might as well try to learn libRocket again, since that would likely be lighter than embedding all of the Chromium engine.

Thanks anyway though.