Function to present few centered lines

Function to present few centered lines

[Jean Louis]

I would like to show few lines in the center of whole monitor window
by using Emacs. And I miss probably knowledge of some built-in
functions.

In this below for now degraded function I do not know how to enlarge
the font so that the (window-width) and (window-height) also change,
so that I can get realistic numbers which I can use to center lines.

What does not work:

- enlarging font, I don't know how to enlarge it, so that width and
  height of window is adjusted to new enlarged font

- centering, I am trying to center line by using window-width and
  setting fill-column, it seem it does not center nicely.

(defun present-snippet (snippet)
  "This is expected to show few lines with large font in the middle
of maximized frame."
  (let* ((snippet (split-string snippet))
	 (buffer (car snippet)))
    (switch-to-buffer-other-frame buffer)
    (set-frame-parameter nil 'fullscreen 'maximized)
    ;; (text-scale-adjust 3) ;; 
    (let* ((width (window-width))
	   (height (window-height))
	   (first-line (- height (length snippet))))
      (mapc 'insert (make-list first-line "\n"))
      (while snippet
	(let* ((line (pop snippet))
	       (line-length (length line))
	       (fill-column width)
	       (place (- (/ width 2) (/ line-length 2))))
	  (insert line)
	  (center-line)
	  (insert "\n"))))))

(present-snippet "Phone: +1234456578")

Re: Function to present few centered lines

[Eli Zaretskii]

> Date: Wed, 14 Apr 2021 16:03:45 +0300
> From: Jean Louis <bugs@gnu.support>
> 
> - enlarging font, I don't know how to enlarge it, so that width and
>   height of window is adjusted to new enlarged font

"Adjusted" in what way? to keep the same number of columns?  I think
you need to manually enlarge the window.

> - centering, I am trying to center line by using window-width and
>   setting fill-column, it seem it does not center nicely.

Why not use center-region?

Re: Function to present few centered lines

[Jean Louis]

* Eli Zaretskii <eliz@gnu.org> [2021-04-14 16:14]:
> > Date: Wed, 14 Apr 2021 16:03:45 +0300
> > From: Jean Louis <bugs@gnu.support>
> > 
> > - enlarging font, I don't know how to enlarge it, so that width and
> >   height of window is adjusted to new enlarged font
> 
> "Adjusted" in what way? to keep the same number of columns?  I think
> you need to manually enlarge the window.

If I do:

(window-width) ⇒ 103
(text-scale-increase 5) ⇒ t
(window-width) ⇒ 103
(progn (insert "Hello") (center-line)) --- it will not show centered
                                    according to text scale increase

What I would like is to get a new (window-width) value adjusted to the
text increased as to calculate more from thre.

> > - centering, I am trying to center line by using window-width and
> >   setting fill-column, it seem it does not center nicely.
> 
> Why not use center-region?

OK that is good idea. In this example I wish to center vertically as
also horizontally, but I can calculate vertical centering, insert
lines, and use center-region, that is fine.

Re: Function to present few centered lines

[Eli Zaretskii]

> Date: Wed, 14 Apr 2021 16:35:45 +0300
> From: Jean Louis <bugs@gnu.support>
> Cc: help-gnu-emacs@gnu.org
> 
> (window-width) ⇒ 103
> (text-scale-increase 5) ⇒ t
> (window-width) ⇒ 103
> (progn (insert "Hello") (center-line)) --- it will not show centered
>                                     according to text scale increase

You need to scale back fill-column, because evidently you want the
text centered in pixel units, not in column units.

> What I would like is to get a new (window-width) value adjusted to the
> text increased as to calculate more from thre.

The problem here is that window-width returns value in canonical
column units, while fill-column measures in actual columns.  So you
are comparing apples with oranges.