Re: Feature request for extra configuration variable.

[Yuan Fu]

> On May 3, 2022, at 4:30 AM, dalanicolai <dalanicolai@gmail.com> wrote:
> 
> As I have already mentioned here before, I have written image-roll.el which 
> provides an 'improved' document 'display engine', to give a better reading 
> scrolling experience. The package already works quite fine for doc-view en 
> pdf-tools. However, there is a remaining issue, for which I have asked some 
> question already here.
> 
> Now I could add extra logic to fix that issue, but I prefer to keep the code 
> as straightforward, clear and simple as possible.
> 
> The issue is due to the behavior, that if some line is already on screen, 
> then, when jumping to that line will not make the line the 'window start'. 
> When jumping to a line that is off-screen the problem does not occur, i.e. 
> Emacs makes it the `window-start` automatically.
> 
> The package is implemented so that each page is (on overlay over) a single 
> line (i.e. a single space). The 'current page' should always be the page 
> at/overlapping with the window start. So when jumping to a next page, the new 
> page (i.e. line) should become the new window start.
> All pages that are 'calculated' to be not 'on-window' (in view) will get 
> 'undisplayed' to save memory.
> 
> So all pages above the 'new current page' get undisplayed, but when the 'new 
> current page' is already within view (on-window), then when we jump to the 
> new page, the page does not become the window start, and the undisplayed 
> pages above it stay visible.
> 
> When I try to use `(set-window-start ...)`, then for some reason subsequently 
> setting `vscroll` does not work.
> Setting vscroll does work after a `(redisplay)` but then the jump becomes 
> very 'ugly’.


Pardon me if I understood you, but have you tried setting NOFORCE argument to 
t? Like so:

(set-window-start nil (point) t)
(set-window-vscroll nil scroll-amount t)

I have code like this running fine for one of my packages, maybe that can solve 
your problem.

Yuan