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

From: Eli Zaretskii
Subject: bug#18422: 24.3.93; Assertion violation when resizing mini-window on a TTY
Date: Sun, 07 Sep 2014 22:23:10 +0300

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 < 

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)
    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 (i686-pc-mingw32)
 of 2014-09-07 on HOME-C4E4A596F7
Repository revision: 117483 address@hidden
Windowing system distributor `Microsoft Corp.', version 5.1.2600
Configured using:
 `configure --prefix=/d/usr --enable-checking=yes,glyphs 'CFLAGS=-O0

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.

(shadow sort gnus-util mail-extr emacsbug message format-spec rfc822 mml
easymenu mml-sec mm-decode mm-bodies mm-encode mail-parse rfc2231
mailabbrev gmm-utils mailheader sendmail rfc2047 rfc2045 ietf-drums
mm-util help-fns mail-prsvr mail-utils time-date tooltip electric
uniquify ediff-hook vc-hooks lisp-float-type mwheel dos-w32 ls-lisp
w32-common-fns disp-table w32-win w32-vars tool-bar dnd fontset image
regexp-opt fringe tabulated-list newcomment lisp-mode prog-mode register
page menu-bar rfn-eshadow timer select scroll-bar mouse jit-lock
font-lock syntax facemenu font-core frame cham georgian utf-8-lang
misc-lang vietnamese tibetan thai tai-viet lao korean japanese hebrew
greek romanian slovak czech european ethiopic indian cyrillic chinese
case-table epa-hook jka-cmpr-hook help simple abbrev minibuffer nadvice
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)
 (floats 8 57 68)
 (intervals 28 238 95)
 (buffers 508 11))

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