This is real cool, but looking at this, it's clear that it doesn't look the way tab widgets are supposed to work. In particular, of course, they should have the proper borders around the stuff displayed. I've attached a screen shot of a typical Windows dialog box with a tab widget in it. The problem lies with this "expanded gutter" concept. Tabs are *NOT* extra graphical junk placed in the gutters of a buffer but are GUI objects with *children* inside of them. This is the right way to do things, and you would need no extra gutter functionality at all for this. You just need to implement the concept of GUI objects containing other GUI objects within them. One such GUI object needs to be a "Emacs-text" GUI object, which is an Emacs window and contains a buffer within it. At this level, you need not be concerned with the complexities of geometry layout. The only change that needs to be made in the overall strategy of frames, windows, etc. is that windows need not be exactly contiguous and tiled, as long as they are contained within a frame. Or more specifically: Given that you could always split a window contained inside a GUI object, we just need to expand things so that each frame has *multiple* hierarchies of windows in it, rather than just one. A hierarchy of windows can nest inside of another window -- e.g. I put a tab widget or a text widget inside of a buffer. This should be easy to implement -- just change things so there are multiple hierarchies of windows where there are one, each (except the top-level one) being rooted inside some other window. Anyone willing to implement this? Andy? Andy Piper wrote: