Re: master 4b5d04b: Use new macro debounce-reduce to make mouse scaling of images more responsive

[Stefan Monnier <monnier@iro.umontreal.ca>]

>>                            #'image--change-size
>>                            (if n
>>                                (- 1 (/ (prefix-numeric-value n) 10.0))
>>                              0.8)))
> This version doesn't discard a sequence of consecutive calls
> where every call is a costly operation.  For example, on slow hardware
> every image resize takes about 1 sec.

I understand that but I don't see why you connect the two:
AFAICT `image--change-size` is a very lightweight function which just
changes one value in a plist.  The costly operation happens later during
redisplay.  So if those consecutive calls happen without any redisplay
between them, you should pay for the costly operation only once.

> Thus when mouse-wheel generates 5 events, this version will wait for
> the next idle time, then will resize the image sequentially 5 times
> during 5 seconds.

I would expect that after the idle time it will call
`image--change-size` five times and then perform one costly
recomputation with the resulting new size.


        Stefan