Re: buffer.c/buffer.h: How to add new buffer-local variables?

[Keith David Bershatsky]

Thank you, Stefan, for the insight regarding how to handle this particular 
issue.  Greatly appreciated!

Keith

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> From:         Stefan Monnier
> Subject:      Re: buffer.c/buffer.h: How to add new buffer-local variables?
> Date:         Sun, 31 Mar 2019 16:02:49 -0400
> 
>> if (!NILP (BVAR (XBUFFER (w->contents), crosshairs))) ...
> 
> Buffer-local variables are appropriate in the `struct buffer` when it's
> likely that most buffers will have their own setting for it.
> 
> For variables that are likely to be used only in some particular
> buffers, or only under some particular circumstances, it can make a lot
> more sense to declare them as global variables and then rely on the
> Elisp side using `make-local-variable` or `make-variable-buffer-local`,
> so you don't pay for that slot in every buffer even tho it's almost
> never used.
> 
>         Stefan