11.12 Possible Future Local Variables

We have considered the idea of bindings that are local to a category of frames--for example, all color frames, or all frames with dark backgrounds. We have not implemented them because it is not clear that this feature is really useful. You can get more or less the same results by adding a function to after-make-frame-functions, set up to define a particular frame parameter according to the appropriate conditions for each frame.

It would also be possible to implement window-local bindings. We don't know of many situations where they would be useful, and it seems that indirect buffers (see section 27.11 Indirect Buffers) with buffer-local bindings offer a way to handle these situations more robustly.

If sufficient application is found for either of these two kinds of local bindings, we will provide it in a subsequent Emacs version.