Re: isearch highlighting

[Richard Stallman]

    > Is it worth doing this now considering that the default value of
    > lazy-highlight-max-at-a-time (20) already provides quite good
    > responsiveness of isearch to key presses.

    If it's responsive enough, then it won't be interrupted by while-no-input.

That is not entirely true.  If it spends even a tiny amount of time
being busy, then it can sometimes be interrupted by while-no-input.
So we would need to do the work to make it use while-no-input
correctly, even if those cases are rather rare.

What does it need to do?  Any input character that triggers
while-no-input will certainly be intepreted by the search command
loop.  Most of the time, this will change the search string.