Highlight/font-lock problem with non-fixed width fonts

[Miguel Frasson <frasson@math.leidenuniv.nl>]

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In GNU Emacs 21.3.1 (i386-redhat-linux-gnu, X toolkit, Xaw3d scroll bars)
 of 2004-04-15 on bugs.devel.redhat.com
configured using `configure  --host=i386-redhat-linux --build=i386-redhat-linux --target=i386-redhat-linux-gnu --program-prefix= --prefix=/usr --exec-prefix=/usr --bindir=/usr/bin --sbindir=/usr/sbin --sysconfdir=/etc --datadir=/usr/share --includedir=/usr/include --libdir=/usr/lib --libexecdir=/usr/libexec --localstatedir=/var --sharedstatedir=/usr/com --mandir=/usr/share/man --infodir=/usr/share/info --with-pop --with-sound'
Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: nil
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: en_US
  locale-coding-system: iso-latin-1
  default-enable-multibyte-characters: t

Please describe exactly what actions triggered the bug
and the precise symptoms of the bug:

Hi.

I am using in some lines (section title in LaTeX-mode in new AUCTeX) a
large non-fixed width font (helvetica) (AUCTeX defaults), and I use also
pc-selection-mode.  I was in a long line, with non-fixed width font, that
is displayed in 2 lines.  I select text in this line such that text in
both displayed lines is highlighted.  Then I delete this text.  Strangely,
there is a tiny (or huge, depending on what is next) area in the end of
the line that is still highlighed.  An undo action, that puts the text
back and does _not_ select anything, does not paint in white again that
region.

What I think that is happening: since the text is in non-fixed font, the
end of the "picture" of the last displayed character in a line does not
coincide with the frame border.  There is a white (bg color) region,
smaller in width than the next character.  This region is not correctly
handled.

A screenshot demonstrating the problem is found in 
  http://www.math.leidenuniv.nl/~frasson/emacs-bug-highlight.png

Best regards.

Miguel.

Recent input:
<down> <up> <up> <home> <C-right> <C-right> <C-right> 
<C-right> <C-right> <C-right> <C-right> <end> <left> 
<left> <left> <left> <left> <left> <left> <left> <left> 
<right> <right> <right> <right> <right> <left> <left> 
<end> <left> <C-S-left> <C-S-left> <S-left> <S-left> 
<S-left> <S-left> <delete> C-_ <backspace> <right> 
<right> <right> <right> <right> <right> <left> <left> 
<left> <left> <left> <left> SPC <C-right> <left> <left> 
<left> <left> <C-S-right> <C-S-right> <C-S-right> <delete> 
SPC / <backspace> m m m m m m m m <C-S-left> <delete> 
C-_ <help-echo> <help-echo> <help-echo> <help-echo> 
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo> 
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo> 
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo> 
<help-echo> <help-echo> <help-echo> <menu-bar> <help-menu> 
<report-emacs-bug>

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