Re: [PATCH] Proposal to change cursor appearance to indicate region activation

[Kelly Dean <kelly@prtime.org>]

David Kastrup wrote:
> Multiple independent use cases.  add-hook/remove-hook is a mechanism for
> organizing independent use cases for one feature, but there is no such
> mechanism for organizing independent use cases for the varhook feature
> in your implementation even though you actually use add-hook.  But it
> requires first individually allocating, naming, and using a hook for any
> variable you might want to varhook into.

IIUC, you mean independent uses of varhook might choose different symbols for the hook. It seems that would be solved by the convention of using the symbol ⌜foo-varhook⌝ as the hook for ⌜foo⌝; all independent uses would add/remove their functions on that same hook.

I guess another solution would be to put the car of the list of functions directly in a dedicated varhook slot for the target symbol, rather than indirecting through a regular hook. That would increase the size of each symbol from 24 to 28 bytes (on 32-bit platforms). But even in my main Emacs session, which has been up for 54 days (with 300MB reserved memory), I only have 10k symbols, so an extra 40kB of memory usage isn't much overhead.