Add support for smooth cursor for emacs 31

[mkvoya]

The smooth cursor feature adds native cursor movement animation for macOS. The feature extends ksqsf's implementation to support more (if not all) kinds of cursors and cursor blinks.

[daviderestivo]

@mkvoya would you be interested in opening a PR for https://github.com/daviderestivo/homebrew-emacs-head as well :)?

[d12frosted]

Hey @mkvoya

Thanks for PR. Two questions:

1. Where did it come from? Are you the original author?
2. Did you propose it to upstream? If yes, can you share a link to communication? If not - why? :)

As a rule of thumb I try to minimise amount of included patches and I prefer people to contribute to the upstream, so wider audience can enjoy improvements. Besides, practically I lack time and knowledge to support non-trivial patches.

[ksqsf]

Hi, I'm the original implementor of the idea, and the original patch is in my own Emacs fork (ksqsf/emacsmoe#7). Recently @mkvoya improved it greatly, sent it to me, and we thought it might be a good idea to share it with greater audience.

1. @mkvoya can be considered a co-author at the very least, or the primary author in its current form at best.
2. No, this feature will not be accepted by the upstream, because it cannot work on "free operating systems". So there's no communication, since we didn't even try. :)

(Also, to the best of my knowledge, it will be quite difficult to implement it for Linux. Maybe a fun challenge, but the gain does not justify the effort. Personally I think we will not see this any time soon on Linux.)

Besides, practically I lack time and knowledge to support non-trivial patches.

This is a very valid concern. My suggestion is to apply this patch to Emacs 30 (rather than HEAD), so that the maintenance burden is minimal. Unfortunately, we cannot guarantee timely updates to the patch, either.

[mkvoya]

The burden of maintaining the patch should not be large, as it involves only code additions, and the patch is quite stable in my nearly two months of daily work. I can maintain the patch if necessary since I am using it myself. By the way, @ksqsf would you please share your email address so that I can list you in the patch's co-authors?

[ksqsf]

The burden of maintaining the patch should not be large, as it involves only code additions, and the patch is quite stable in my nearly two months of daily work. I can maintain the patch if necessary since I am using it myself. By the way, @ksqsf would you please share your email address so that I can list you in the patch's co-authors?

gmail beginning with justksqsf