Re: Use cases for post-redisplay hooks

[Keith David Bershatsky <esq@lawlist.com>]

With my limited computer skills, I was not able to find the "sweet spot" in the redisplay code where I knew for sure that `window-start' and `window-end' were always going to be correct such that I could easily set a hypothetical `needs-recalculation' flag to `nil'.  When I tried applying overlays too late in time in the redisplay cycle, there were visual problems updating the screen.

With my custom `window-start-end-hook' (with accepts a function with arguments for `window-start' and `window-end'), I use a test (built into the C code) to see whether point is fully visible before I run the Lisp function attached to the hook.  However, it assumes that `make-cursor-line-fully-visible' remains set at the default value of `t'.  I use `(setq scroll-conservatively 101)'.  On my todo-list, is to figure out how to incorporate a test (akin to `needs recalculation') for when `make-cursor-line-fully-visible' is set to `nil'.  Essentially, redisplay does less work when `make-cursor-line-fully-visible' is `nil'.  I've been using a custom build of Emacs with the `window-start-end-hook' since shortly after generating Emacs feature request 22404.

Keith

At Thu, 7 Jul 2016 15:44:13 -0400,
Clément Pit--Claudel wrote:
> 
> But I meant ­— can't you update this flag yourself, and do at most one recalculation per command loop?