I'm not sure I understand the question. Are you saying that if you ignore
the line overflow, termination of a line, etc., you can write code that does
display characters column-wise?

I thought that displaying line row wise is the "base" of the display_line function with code for

line truncation, overflow, bidi etc added on top of it in "if" blocks, so if I could just get the base to work (i.e. displaying lines in a column)

then I could work on the the finer details.

Am I wrong?

In any case, it is hard to discuss this without seeing the code which
doesn't work. Is the code you wrote available anywhere for review?

Unfortunately it is no longer available.

One line which I remember causing a problem though was line 24500 in src/xdisp.c

row->y = it->current_y;

if I changed it to: row->x = it->current_x; Emacs no longer displays characters.

On Sun, Nov 20, 2022 at 5:13 PM Eli Zaretskii <eliz@gnu.org> wrote:

> From: समीर सिंह Sameer Singh <lumarzeli30@gmail.com>
> Date: Sun, 20 Nov 2022 16:48:31 +0530
> Cc: emacs-devel@gnu.org
>
> I tried writing a vertical version of the display_line function but could not get it to work. Emacs does not
> display any character after these changes.
> (maybe I should have also rewrote move_it_in_display_line_to?)

I don't think move_it_in_display_line_to is relevant at this early stage of
your work.

> Therefore forgive me for asking again, if for now I just want to make the characters appear column wise
> instead of row wise, disregarding line overflow, or termination of a line etc,
> do I still have to look into the display_line function, because as I recall I had once removed most of the lines
> of the display_line function and Emacs was still displaying lines fines.

I'm not sure I understand the question. Are you saying that if you ignore
the line overflow, termination of a line, etc., you can write code that does
display characters column-wise?

In any case, it is hard to discuss this without seeing the code which
doesn't work. Is the code you wrote available anywhere for review?