Re: SVG widget in GNU Emacs

[Eli Zaretskii]

> From: Po Lu <luangruo@yahoo.com>
> Cc: emacs-devel@gnu.org,  atamariya@gmail.com
> Date: Wed, 20 Oct 2021 20:48:15 +0800
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > From my POV, the xwidget feature is incomplete and not maintained very
> > well.  As long as this is the case, extending such an incomplete
> > feature is waste of our resources.
> 
> I'm not sure I understand why the xwidget feature would be incomplete.

Here's an example:

  static int
  scrolling_window (struct window *w, int tab_line_p)
  {
   ...
  #ifdef HAVE_XWIDGETS
    /* Currently this seems needed to detect xwidget movement reliably.
       This is most probably because an xwidget glyph is represented in
       struct glyph's 'union u' by a pointer to a struct, which takes 8
       bytes in 64-bit builds, and thus the comparison of u.val values
       done by GLYPH_EQUAL_P doesn't work reliably, since it assumes the
       size of the union is 4 bytes.  FIXME.  */
      return 0;
  #endif

This disables one of the more important display optimizations in an
Emacs compiled with xwidgets support.

> It seems to work OK for what it is currently intended to do: display web
> content in an Emacs buffer.
> 
> But I'm probably missing something here.  Could you please elaborate
> further?  Thanks.

Apart of the above, just look at xwidget.c and xwidget.el, and you
will see the FIXMEs, the incomplete doc strings, and other stuff left
unfinished.  The idea was that those will get finished once the
feature is in the sources, but unfortunately it didn't happen.