part of display property on before-string property is not displayed

[Joe Wells]

When a string is the display property of a portion of a before-string
property of an overlay, part of the display property can disappear.
In this case the first character of the display property does not get
shown.

Reproduce by evaluating this code:

  (let ((buf (get-buffer-create "foo")))
    (with-current-buffer buf
      (display-buffer buf)
      (erase-buffer)
      (dolist (o (overlays-in (point-min) (point-max)))
        (delete-overlay o))
      (insert "ABC")
      (let ((o (make-overlay 2 3))
            (s (copy-sequence "DEF")))
        (put-text-property 1 2 'display "123" s)
        (overlay-put o 'display "Y")
        (overlay-put o 'before-string s))))

You will see the “foo” window pop up and in the window you will see
“AD23FYC”.  I expected that instead “AD123FYC” would be shown.

This seems like a bug.

Thanks for your time in considering this bug report.

Joe

======================================================================
In GNU Emacs 22.1.1 (i686-pc-linux-gnu, GTK+ Version 2.8.20)
 of 2007-06-27 on artemis
Windowing system distributor `The X.Org Foundation', version 11.0.70000000
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'--disable-nls' '--with-x-toolkit=gtk' 'CFLAGS=-O0 -g3 -ggdb''

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