Re: scroll-down with pixel transition

[Tak Kunihiro]

>> I meant a line with “(dir)Top” will not be shown by 
>> pixel-scroll-down-and-set-window-vscroll.  I suppose you refer the line as 
>> “breadcrumbs”.
>> 
>> emacs -Q
>> M-x load-file RET pixel-scroll.el RET
>> M-x info
>> C-s gnus RET
>> M-x pixel-scroll-down
>> M-x pixel-scroll-down
>> M-x pixel-scroll-down
> 
> You need to carefully examine the behavior of the functions you use
> near that special place, as some of them might behave unexpectedly
> when an overlay string is present that hides some of the buffer text,
> which makes the effect of these functions not well-defined.
> 
> The diffs below should give you a start, but there still are some
> minor glitches near the beginning of an Info node; these are left as
> exercises ;-)
> 
> --- pixel-scroll.el~0 2017-04-16 13:19:06.708750000 +0300
> +++ pixel-scroll.el   2017-04-17 11:48:10.661875000 +0300
> @@ -235,7 +235,15 @@
>   (let ((pos
>          (save-excursion
>            (goto-char (window-start))
> -           (beginning-of-visual-line 0))))
> +        (if (bobp)
> +            (point-min)
> +          ;; When there's an overlay string at window-start,
> +          ;; (beginning-of-visual-line 0) stays put.
> +          (let* ((ppos (point))
> +                 (tem (beginning-of-visual-line 0)))
> +            (if (eq tem ppos)
> +                (vertical-motion -1))
> +            (point))))))
>     (set-window-start nil pos t)
>     (set-window-vscroll nil vscroll t)))

Thank you very much!  

I start to test pixel-resolution-fine-p t.  Even typing C-n or
C-p after a pixel scroll shifts text a little, it seems that
the itch does not bother me much. 

I plan to revise the code and come back on this weekend.