Re: redisplay flicker

[Alex Schroeder]

d.love@dl.ac.uk (Dave Love) writes:

> [In Emacs 21.1, as modified by Debian.]
>
> I have a buffer (*compilation*) full of overlays in a remote-running
> Emacs (Debian testing) displayed under X (Debian stable) over a 10Mb
> network link which probably isn't very busy.  The display flickers
> annoyingly.  When the frame gets the focus it's worse -- the overlay
> under the mouse positively throbs.
>
> I don't see the same with a local display, so I assume it's due to
> network bandwidth and that it would be worse over a slower network.
>
> This turns out to be a function of blink-cursor mode.  Turning that
> off stops the flicker.  I don't know why this hasn't bothered me
> before...

I have blink-cursor-mode set to nil, and have some weird blinking to
report.  I don't know wether it has been fixed in CVS already, I
faintly remember a bug report related to blinking.  Perhaps somebody
can tell -- or send me a patch to try?

On Emacs 21.1, on Debian Potato, but compiled from 21.1 sources by
myself, I use a slow network connection to a remote system (actually,
I'm playing on a MUSH).  The buffer uses comint-mode and
ansi-color-mode.  Thus, ANSI escape sequences get turned into
overlays.  Just yesterday it just so happened that I had about 20
lines of text in that buffer.  Every line started with a piece of text
covered by an overlay with the 'face property set to 'modeline.

It kind of looked like this:

MODELINEFACE other text in default face
MODELINEFACE other text in default face
MODELINEFACE other text in default face
MODELINEFACE other text in default face
MODELINEFACE other text in default face
MODELINEFACE other text in default face
MODELINEFACE other text in default face
MODELINEFACE other text in default face

And now the weirdest blinking started.

My mode-line face looks like this:  Occasionally, the foreground of
one of these overlays would loose the foreground!  Thus,  any single
one of MODELINEFACE would still have a green background, but no text
in it.  After several seconds the text would reappear.  After some
more (random?) time, another overlay would loose the foreground.

I'd like to help debug this, but I wouldn't know where to start.

The reason I'm writing is that it seemed to be related to network
connections and overlays...  At least I have never seen such behaviour
in my shell-mode buffers (which also use ansi-color-mode).
Perhaps it is also a dependant on the overlay.  In shell-mode buffers
I never use the :box attribute, but when I'm playing on the MUSH, I'm
using the mode-line face which uses the :box attribute.  Perhaps the
:box attribute can lead to blinking?

Attributes: [ ] Font family: Value Menu *
            [ ] Width: Value Menu *
            [ ] Height: Value Menu *
            [ ] Weight: Value Menu *
            [ ] Slant: Value Menu *
            [ ] Underline: Value Menu *
            [ ] Overline: Value Menu *
            [ ] Strike-through: Value Menu *
            [X] Box around text: Value Menu Box:
                Width: -1
                Color: Value Menu *
                Style: Value Menu Raised
            [ ] Inverse-video: Value Menu *
            [X] Foreground: Value Menu Color: wheat       (sample)
            [X] Background: Value Menu Color: dark olive green  (sample)
            [ ] Stipple: Value Menu *
            [ ] Inherit:
                INS

Alex.
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