bug#56815: 29.0.50; Isearch lazy-highlight highlights too much when truncate-lines is in effect

[Gregory Heytings]

> > Would it be possibly to make the isearch lazy-highlight just skip the 
> > portions of the buffer that aren't visible?
>
> Indeed what is worth trying is to add pos-visible-in-window-group-p 
> either to isearch-filter-predicate, or directly to 
> isearch-lazy-highlight-search.

That wouldn't work alas.

The problem is how "visible" is defined here (by pos-visible-in-window-p). 
With truncated lines, all buffer positions between window-start and 
window-end are "visible", or IOW, all buffer positions on the left or 
right of the actually visible line portion are "visible".

Moreover pos-visible-in-window-p is a slow function, so it would be 
terribly slow to call it for each candidate position in a buffer with 
(tens of) thousands of candidate positions.