bug: overlay display artifact: trace left behind

bug: overlay display artifact: trace left behind

[Drew Adams]

[-- Attachment #1: Type: text/plain, Size: 1128 bytes --]

See attached image. The red traces are left behind by just moving a
one-character red overlay across the line (I removed the overlay at the
end). Clearing the display (`C-l') removes the trace, but it is still
annoying.

Notice that the trace is left only between certain pairs of characters, and
that doesn't seem to have to do with the appearance of the characters,
because lowercase and uppercase versions of the same letter act the same.
For instance, there is no trace between the `T' and `Y' in `WARRANTY', and
the same is true of the `t' and `y' in `warranty'.

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

I thought this might also be behind the problem I reported in thread
"two-pixel trace left when move overlay" (April 2006), but that problem
occurs only when `indent-tabs-mode' is nil. This new problem remains even if
I set `indent-tabs-mode' to t.


In GNU Emacs 22.0.50.1 (i386-msvc-nt5.1.2600)
 of 2006-07-19 on BOS-CTHEWLAP2
X server distributor `Microsoft Corp.', version 5.1.2600
configured using `configure --with-msvc (12.00)'

[-- Attachment #2: bug-overlay-artifact.jpg --]
[-- Type: image/jpeg, Size: 81827 bytes --]

[-- Attachment #3: Type: text/plain, Size: 142 bytes --]

_______________________________________________
Emacs-devel mailing list
Emacs-devel@gnu.org
http://lists.gnu.org/mailman/listinfo/emacs-devel

Re: bug: overlay display artifact: trace left behind

[Richard Stallman]

    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.

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.

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:

         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.

      Kim> If I try this on GNU/Linux with the code you sent me
      for the "overlay at mouse-2 yank position", I don't see
      the problem. Do you have a simple test case that I can try?

  Sent: Wednesday, August 16, 2006 7:22 AM
  No, sorry, not simpler than that. Perhaps this is Windows-only.

I neglected to cc the list when I replied to Kim. Any chance that someone
has tried this on MS Windows?