Subject: bug#18422: closed (Re: bug#18422: 24.3.93; Assertion violation when resizing mini-window on a TTY)

From: [email-masked] (GNU bug Tracking System)
Date: Thu, 11 Sep 2014 16:41:03 +0000

Your bug report

#18422: 24.3.93; Assertion violation when resizing mini-window on a TTY

which was filed against the emacs package, has been closed.

The explanation is attached below, along with your original report.
If you require more details, please reply to [email-masked].

-- 
18422: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=18422
GNU Bug Tracking System
Contact [email-masked] with problems

Subject: Re: bug#18422: 24.3.93; Assertion violation when resizing mini-window on a TTY
From: martin rudalics <[email-masked]>
To: Eli Zaretskii <[email-masked]>
Cc: [email-masked]
Date: Thu, 11 Sep 2014 18:40:02 +0200
List-Id: <debbugs-submit.debbugs.gnu.org>

> Thanks, it works for me.  You can close the bug, unless you think
> something else needs to be done.

Closing.

Thanks, martin

Subject: 24.3.93; Assertion violation when resizing mini-window on a TTY
From: Eli Zaretskii <[email-masked]>
To: [email-masked]
Date: Sun, 07 Sep 2014 22:23:10 +0300
List-Id: <debbugs-submit.debbugs.gnu.org>

The following recipe causes an assertion violation on MS-Windows (I
don't have access to a Unix TTY with a mouse to try there):

  emacs -Q -nw
  M-: (setq resize-mini-windows nil) RET

  Drag the mode line with the mouse -- you get assertion violation:

    dispnew.c:684: Emacs fatal error: assertion failed: start >= 0 && start < matrix->nrows

The immediate reason for this is that clear_glyph_matrix_rows is
called with both start = 0 and end = 0.  But the root cause is that
Emacs thinks the mini-buffer window has a zero height.  This comes
from here:

  static int
  required_matrix_height (struct window *w)
  {
  #ifdef HAVE_WINDOW_SYSTEM
    struct frame *f = XFRAME (w->frame);

    if (FRAME_WINDOW_P (f))
      {
	int ch_height = FRAME_SMALLEST_FONT_HEIGHT (f);
	int window_pixel_height = window_box_height (w) + eabs (w->vscroll);

	return (((window_pixel_height + ch_height - 1)
		 / ch_height) * w->nrows_scale_factor
		/* One partially visible line at the top and
		   bottom of the window.  */
		+ 2
		/* 2 for header and mode line.  */
		+ 2);
      }
  #endif /* HAVE_WINDOW_SYSTEM */

    return WINDOW_TOTAL_LINES (w); <<<<<<<<<<<<<<<<<<<<<
  }

The total_lines value is zero.  It turns out that total_lines is
assigned the zero value in resize-mini-window-internal:

      w->total_lines = XFASTINT (w->new_total);  <<<<<<<<<<<<<<
      w->pixel_height = XFASTINT (w->new_pixel);

and w->new_total is zero because no one set it to any other value.  In
window--resize-mini-window we do this:

	(window--resize-this-window root (- delta) nil nil t)
	(set-window-new-pixel window (+ height delta))
	;; The following routine catches the case where we want to resize
	;; a minibuffer-only frame.
	(when (resize-mini-window-internal window)
	  (window--pixel-to-total frame)

So by the time resize-mini-window-internal is called, w->new_pixel is
already set as appropriate, but w->new_total is set only after the
call to resize-mini-window-internal returns.

Now, on GUI frames this problem doesn't happen, because, as seen from
required_matrix_height above, total_lines is never used there to
determine the matrix dimensions.  Instead, GUI frames calculate their
height in pixels, which is already set by this time.

I can fix this problem with the following semi-kludgey change (which
will need a comment to explain the above, if and when it's committed):

=== modified file 'src/window.c'
--- src/window.c	2014-08-09 11:12:45 +0000
+++ src/window.c	2014-09-07 19:19:19 +0000
@@ -4807,6 +4807,8 @@ DEFUN ("resize-mini-window-internal", Fr
       w->total_lines = XFASTINT (w->new_total);
       w->top_line = r->top_line + r->total_lines;
       w->pixel_height = XFASTINT (w->new_pixel);
+      if (!FRAME_WINDOW_P (f))
+	w->total_lines = w->pixel_height;
       w->pixel_top = r->pixel_top + r->pixel_height;
 
       fset_redisplay (f);

Is this the right fix?

In GNU Emacs 24.3.93.28 (i686-pc-mingw32)
 of 2014-09-07 on HOME-C4E4A596F7
Repository revision: 117483 [email-masked]
Windowing system distributor `Microsoft Corp.', version 5.1.2600
Configured using:
 `configure --prefix=/d/usr --enable-checking=yes,glyphs 'CFLAGS=-O0
 -g3''

Important settings:
  value of $LANG: ENU
  locale-coding-system: cp1255

Major mode: Lisp Interaction

Minor modes in effect:
  tooltip-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

Recent input:
M-x r e p o r t - e m a c s - b u g <return>

Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.

Load-path shadows:
None found.

Features:
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uniquify ediff-hook vc-hooks lisp-float-type mwheel dos-w32 ls-lisp
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loaddefs button faces cus-face macroexp files text-properties overlay
sha1 md5 base64 format env code-pages mule custom widget
hashtable-print-readable backquote make-network-process w32notify w32
multi-tty emacs)

Memory information:
((conses 8 74225 7254)
 (symbols 32 17536 0)
 (miscs 32 33 97)
 (strings 16 10776 4344)
 (string-bytes 1 269292)
 (vectors 8 9555)
 (vector-slots 4 384789 5962)
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 (buffers 508 11))