Re: Alternative to current-column that counts from visual line beginning

[Eli Zaretskii]

On December 29, 2020 7:01:16 AM GMT+02:00, Yuan Fu <casouri@gmail.com> wrote:
> 
> 
> > On Dec 28, 2020, at 9:40 PM, Stefan Monnier
> <monnier@iro.umontreal.ca> wrote:
> > 
> >> to get the column number counting from the visual line beginning.
> Is
> >> there a function that does what I want? If not, maybe we should add
> >> one, or add an argument to current-column.
> > 
> > `posn-at-point`?
> > 
> 
> That works, albeit a bit convoluted comparing to current-column and
> only works when point is visible. Another less legit point is that
> posn-at-point is a bit far-fetched semantically: for me it is more
> about GUI pixel positions than text-based column and line positions.
> All things considered, I still prefer a dedicated function or an
> additional argument to current-column.
> 
> Yuan

The concept of "visual line" of some buffer position only makes sense in the 
context of displaying the buffer in some window.  That's because window 
dimensions and other window-specific aspects, such as faces and overlays, have 
direct and prominent effect on how physical lines are divided into visual lines.

Therefore, I don't think I understand how can a function exist that reports the 
"visual column" of a buffer position without telling it the window in which to 
display that buffer.  Could you perhaps outline the algorithm for such a 
function?  Perhaps there is some misunderstanding.