Hi,
Here is my Project.
I had not the time to clean the code. It is a bit unclean here and there.
To test my modifications you have to run the "render.c".
I used your split scripts, because SED realy sucks when you open big files.
Until now I only modified "lbgui_windowfunc.h":
I copied "LBG_window_border_bitmap" function to(LBG_window_border_bitmap_n)
and
"LBG_window_content_bitmap" function to(LBG_window_content_bitmap_n)
you will see.
The panels (content and panel) still have the bitmaps attached. With the window elements, you could delete them completly, of yourse with backward compatibility in mind you should not.

Link: Project

I have a small problem with your gui system.
- My mouse Mode is 4
- I am in fullscreen mode
- A mouse_map is attached
Problem: The mouse flickers when I am on top of the titlebar

MfG,
Me