Display can be corrupted when scrolling mixed character sets with large print

This bug report will be sent to the XEmacs Development Team, not to your local site managers!! Please write in English, because the XEmacs maintainers do not have translators to read other languages for them. In XEmacs 21.4 (patch 4) "Artificial Intelligence" [Lucid] (i386-debian-linux, M ule) of Mon Jul 30 2001 on eeyore configured using `configure --with-sound=native,esd '--cflags=-O2 -g -Wall ' --w ith-x11 --extra-verbose --with-site-lisp --statedir=/var/lib --infodir=/usr/shar e/info/xemacs-21.4.4 --prefix=/usr --error-checking=none --debug=no --dynamic -- without-postgresql --with-gpm=no --with_menubars=lucid --with_scrollbars=lucid - -with_dialogs=athena --docdir=/usr/lib/xemacs-21.4.4/i386-debian-linux/mule/ --w ith-mule --with-canna=no --with-wnn=no --with-xim=xlib --with-xfs '--package-pat h=~/.xemacs:~/.xemacs/packages::/usr/share/xemacs21/packages:/usr/share/xemacs21 /mule-packages:/usr/share/xemacs21/site-packages' i386-debian-linux' Please describe exactly what actions triggered the bug and the precise symptoms of the bug: Display can be corrupted when scrolling mixed character sets with large print. To reproduce, first execute this Lisp (I don't think the bug is specific to these fonts, but these are the ones I used): (set-face-font (make-face 'default) (make-font-instance "-*-fixed-medium-r-norma l-*-20-*-100-*-c-*-*-*")) (set-face-font (make-face 'modeline) (make-font-instance "-*-helvetica-bold-r-no rmal-*-*-160-*-*-p-*-iso8859-1")) Then put lots of text in an empty buffer (must be more text than will fit on the screen, so can do scrolling.) Then add some Simplified Chinese characters on the first line (the bug is not limited to Simplified Chinese or to the first line, but this is what I did). For example, invoke the Hello program (M-? h), copy the line saying "Chinese", and yank it into the buffer. Then execute the following Lisp (in that buffer) to make the Chinese characters large print: (set-face-font (make-face 'default) (make-font-instance "-isas-song ti-medium-r-normal-*-*-240-*-*-c-*-gb2312.1980-0") (current-buffer)) Then split the frame (Ctrl-x 2). Then move the mouse pointer to the top left corner of the BOTTOM window (lower half of the frame), click, and drag the pointer down to the very bottom of the desktop (below the emacs frame, so that the buffer starts scrolling down a line at a time). You should see that the modeline between the two frames gets partly overwritten with the Chinese characters. (Ctrl-L restores it.) (The display also gets corrupted if you do the top window instead of the bottom one, but the effect isn't quite so obvious.) Recent keystrokes: down down up C-home button1 button1up Sh-next Sh-prior up Sh-down Sh-down Sh-down Sh-down Sh-down down down up C-home button1 button1up button1 button1up C-l button1 button1up button1 button1up C-l C-home M-x s c r TAB o l TAB d TAB TAB TAB RET down down down M-x up RET down M-x up - TAB o TAB RET up down M-x c u r TAB TAB BS BS BS TAB i BS BS w i TAB TAB n TAB TAB d TAB TAB C-] up up up up up button1 button1up button1 button1up button1 button1up button1 button1up button1 button1up button1 button1up misc-user Recent messages (most recent first): Loading emacsbug...done Loading emacsbug... Quit Making completion list... Making completion list... Making completion list... Making completion list... Making completion list... Making completion list... Deleted messages expunged. -- Silas S Brown, St John's College Cambridge UK http://www.cus.cam.ac.uk/~ssb22 "He that is hastening to get riches will not remain innocent" - Proverbs 28:20