Public bug reported:
Binary package hint: xserver-xorg-video-neomagic
Running lubuntu-desktop on Ubuntu 11.04 (natty)
xserver-xorg-video-neomagic: 1:1.2.5-1ubuntu3
# lspci | grep VGA
01:00.0 VGA compatible controller: Neomagic Corporation NM2360 [MagicMedia
256ZX]
# xrandr -q
xrandr: Failed to get size of gamma for output default
Screen 0: minimum 320 x 240, current 1024 x 768, maximum 1024 x 768
default connected 1024x768+0+0 0mm x 0mm
1024x768 60.0*
800x600 60.0 56.0
640x480 60.0
320x240 60.0
# grep visual /var/log/Xorg.0.log
[ 41.018] (==) NEOMAGIC(0): Default visual is TrueColor
# grep Depth /var/log/Xorg.0.log
[ 41.018] (**) NEOMAGIC(0): Depth 16, (--) framebuffer bpp 16
# grep DPI /var/log/Xorg.0.log
[ 41.065] (==) NEOMAGIC(0): DPI set to (96, 96)
# glxinfo | grep direct
direct rendering: Yes
---
Issues:
When setting wallpaper (via pcmanfm) or looking at png/jpeg (in GPicView) which
contains some kind of gradient/fading color, there's a very noticeable and very
ugly "banding" or "striping" instead of a smooth transition/blending between
colors. For example, with the default background in Lubuntu (
/usr/share/lubuntu/wallpapers/lubuntu-default-wallpaper.png ), background set
by default via pcmanfm looks like it is being viewed in 256 color, rather than
16 or 24 bit.
The same wallpaper, same file/size, used by lxdm (LXDE Desktop Manager)
looks absolutely fine at login stage, but not on the background which is
set by pcmanfm, which one sees once logged in.
# ls -l /usr/share/lxdm/themes/Lubuntu/wall.png
-rw-r--r-- 1 root root 264722 2011-01-16 20:03
/usr/share/lxdm/themes/Lubuntu/wall.png
# ls -l /usr/share/lubuntu/wallpapers/lubuntu-default-wallpaper.png
-rw-r--r-- 1 root root 264722 2011-01-16 20:03
/usr/share/lubuntu/wallpapers/lubuntu-default-wallpaper.png
The same "banding" issue appears when opening the files in GPicView.
However, it looks absolutely fine in `feh` (image viewer/background
setter), in gimp, and in firefox4.
The behavior is not specific to these backgrounds, as I've looked at
several other wallpapers w/ gradients that are supposed to look fine,
and the issue persists with the said applications (pcmanfm, GPicView).
The behavior is also not specific to the laptop's (1024x768) LCD screen,
as I've connected a Samsung LCD (SyncMaster 920NW) to the laptop and
seen the same exact degree of gradient-color-banding on it as well.
Upon further testing, the issue is exacerbated when I set the
DefaultDepth 24 in xorg.conf (and 24bpp depth confirmed from Xorg log).
That is, after stop/start lxdm - which was okay at 16bpp - it would then
show the severe banding/striping of gradient colors as well. This lead
me to believe is not an application specific bug, but an issue with
xorg's neomagic video driver.
Regardless of using a custom xorg.conf or conf-less Xorg (which defaults
to 16bpp depth), the issue remains. I've tried disabling various
neomagic-specific acceleration options (as detailed in `man neomagic`)
one by one, tried disabling acceleration altogether, tried starting X
with and without neofb framebuffer-console driver loaded (though I
cannot use Option ShadowFB - which is disabled by default - in xorg.conf
because I get blank screen with it enabled when neofb is also loaded.)
Tried using DirectColor rather than TrueColor for the screen's visual,
but that does not really work correctly on this chipset (neither in 16
or 24 bit depth).
** Affects: xserver-xorg-video-neomagic (Ubuntu)
Importance: Undecided
Status: New
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which is subscribed to xserver-xorg-video-neomagic in Ubuntu.
https://bugs.launchpad.net/bugs/780074
Title:
[neomagic] Gradient color banding/striping on Dell Latitude CPt/CPx
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