Thank you, Eli.

On Fri, Aug 11, 2017 at 7:08 PM, Eli Zaretskii <eliz@gnu.org> wrote:

> > From: Itai Berli <itai.berli@gmail.com>
> > Date: Fri, 11 Aug 2017 18:34:08 +0300
> > Cc: Emacs developers <emacs-devel@gnu.org>
> >
> > > Tell me what you want to do and with what text, and then I might be
> able to help you do
> > that in a more useful way.
> >
> > I just want to get more familiar with the bidi algorithm and the way it
> is implemented by Emacs. I'd like to try
> > various small phrases, such as the ones that can be found in this
> article:
> > https://www.w3.org/International/articles/inline-bidi-markup/uba-basics
>
> After entering GDB, set a breakpoint in a function called
> Fredraw_display, then run Emacs ("run -Q").  Insert the text you want,
> then move point to its beginning and type "C-x =".  Remember the
> buffer position displayed as result, let's call it POS.
>
> Then type "M-x redraw-display RET".  GDB will get control, and you can
> now put breakpoints where you want.  For tracing through the bidi.c
> code, I'd suggest this:
>
>   (gdb) break bidi_get_next_char_visually if bidi_it->charpos == POS
>   (gdb) continue
>
> When the breakpoint in bidi_get_next_char_visually breaks, you can
> step through the code using the "step" and "next" commands (you have
> tool-bar buttons for them).
>
> Note that bidi_get_next_char_visually is called for each character the
> display engine wants to display, so when it returns, it puts in
> bidi_it->charpos the position of the next character in visual order.
>