bug#61558: 29.0.60; Indentation with c-ts-mode doesn't work in code guarded by #ifdef..#endif

[Eli Zaretskii]

> From: Theodor Thornhill <theo@thornhill.no>
> Cc: 61558@debbugs.gnu.org
> Date: Sat, 18 Feb 2023 22:30:06 +0100
> 
> >> Typing RET at the end of the two marked lines goes to column zero
> >> instead of the expected non-zero column.  So it sounds like #define
> >> and #undef are also not handled correctly yet.
> >
> > Yeah, luckily it indents correctly after you start to type.  I'll try to
> > see if I can make some specific handling for this.
> >
> > Theo
> >
> 
> Scratch that.  Can you test this for me?  I think I got it.

Thanks, this seems to work better.  Some problems still remain,
though.

Line 807 of dispnew.c:

#if defined (HAVE_WINDOW_SYSTEM) && ! defined (HAVE_EXT_TOOL_BAR)
  /* Clear the matrix of the tool-bar window, if any.  */
  if (WINDOWP (f->tool_bar_window))   <<<<<<<<<<<<<<<<<<
    clear_glyph_matrix (XWINDOW (f->tool_bar_window)->current_matrix);
#endif

Type RET at the end, then type '{' and RET.  The '{' gets indented
correctly, but there's no additional two-column indent after RET that
follows '{'.

RET after preprocessor directives outside of functions indents by 2
columns.  For example, here:

#if 0
/* Swap glyphs between two glyph rows A and B.  This exchanges glyph
   contents, i.e. glyph structure contents are exchanged between A and
   B without changing glyph pointers in A and B.  */

If you type RET after "#if 0", point goes to column 2, not zero.
Interestingly, if you type RET at the end of the last line of the
following comment, point goes to column zero, as expected.

Line 1357 of dispnew.c:

static void
free_glyph_pool (struct glyph_pool *pool)
{
  if (pool)
    {
#if defined GLYPH_DEBUG && defined ENABLE_CHECKING  <<<<<<<<<<<<<<<
      /* More freed than allocated?  */
      --glyph_pool_count;
      eassert (glyph_pool_count >= 0);
#endif
      xfree (pool->glyphs);
      xfree (pool);
    }
}

Type RET at the end of the indicated line: point goes to column 6, as
expected.  But if you then type "{ RET", point gets indented by 4
columns, not by 2.  And even typing a semi-colon afterwards doesn't
fix the indentation.

Similarly here:

static void
adjust_frame_glyphs_for_window_redisplay (struct frame *f)
{
  eassert (FRAME_WINDOW_P (f) && FRAME_LIVE_P (f));

  /* Allocate/reallocate window matrices.  */
  allocate_matrices_for_window_redisplay (XWINDOW (FRAME_ROOT_WINDOW (f)));

#if defined (HAVE_X_WINDOWS) && ! defined (USE_X_TOOLKIT) && ! defined (USE_GTK)
  /* Allocate/ reallocate matrices of the dummy window used to display
     the menu bar under X when no X toolkit support is available.  */
  {  <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
    /* Allocate a dummy window if not already done.  */
    struct window *w;
    if (NILP (f->menu_bar_window))

The indicated line is 2166 in dispnew.c.  If you type RET there, point
will be indented to column 6, not 4 as expected.  And if you type RET
at the end of the following comment line, not only will point be
over-indented, but the comment itself will also be reindented
incorrectly.

Anyway, this works much better than the original code, and I saw no
regressions, so I think you should install this.  Perhaps consider
adding comments explaining any tricky parts of handling this, so that
future hackers will know what to do and what to avoid.  Bonus points
for adding tests for this, so that we don't easily regress in the
future.

Thanks!