RE: bug: overlay display artifact: trace left behind

[Drew Adams]

        I started with emacs -Q, and just repeatedly used a command
        that moved a one-character overlay to the right one character.

    Can you please send a precise, complete test case?
    Please don't ask us to write our own command to test this.
    The bug might depend on some detail you did not mention.

1. emacs -Q

2. Load this file:
http://www.emacswiki.org/cgi-bin/wiki/mouse%2b.el

3. Customize this face to have a red foreground:
`mouse-flash-position'. (The default, yellow, is not very visible against an
emacs -Q background.)

4. M-: (global-set-key [down-mouse-2] 'mouse-flash-position)

5. Select some text (e.g. a word), for yanking elsewhere.

6. Put the mouse on some line of text. Press `mouse-2' and hold it pressed.
Move the mouse along the text without releasing the button. Release it to
finish the yank.

When you press `mouse-2', the yank position is highlighted. When you move
the mouse, the highlight moves with the mouse. But vestigial overlay traces
are left behind.