[H-GEN] Problem with ViewSonic VG171b how to diagnose?

[Sarah Hollings]

Raymond Smith wrote:

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> 
> Hiya,
> 
> So I have this lovely monitor in front of me in my temporary office.
> And RedHat 9's condiguration software has done a remarkably good job
> of detecting it and all is wonderful at 1028x1024. Except: the grey
> 'moire' pattern on things like the Athena scroll widgets looks like
> it is 'moving'/unstable.
> 
> In fact, so far, xterm scrollbars are the only place that seems to
> have a problem.
> 
> Any ideas how I should go about diagnosing/correcting this problem?
> (besides xterm +sb which is a good workaround for a monitor that I
> will only have for a few days[1]).
> 
> Cheers,
> 
> Raymond
> [1] I wonder if they'd notice if I took it back with me? It really is
>     a very nice monitor :-)

I got zip from my nice new LCD monitor at work under Linux when running 
DVI.  It just did not work.

Switched to VGA (dsub connector) and it was mostly good.  After much 
googling I came up with two general threads:

     thread 1)  some complex stuff involving calculating modelines
                and using xvidtune to tweak the results;

     thread 2)  dont bother, the video card uses DDC probing and will
                set it all up for you

I got less than optimal results so I did fiddle with 
/etc/X11/XF86Config-4 a bit, following some of the tips here:

       http://www.comp.leeds.ac.uk/jj/linux/tftmodeline.html

and really didnt improve things.  I found xvidtune was useless with my LCD.

What may improve things is trying the "DPMS" option, or changing the 
color depth its runnign at (see the Screen stanza below).  Try 24, 16, 
15 and 8 in order as defaults to see if there's any improvement.

To try these ideas, create another stanza (in addition to any other 
Monitor stanza) in the XF86Config file that looks like this to define 
the monitor:
------8<-------------------------------------
Section "Monitor"

     Identifier "VG171b"
     VendorName "Viewsonic"
     ModelName  "TFT"

     # Viewsonic's website has a bit of info, incl hz and vz sync:
     # http://www.viewsonic.com/products/lcd_vg171b.htm
     HorizSync  30-82
     VertRefresh 50-75
     # some googling suggests this line is important
     Option "DPMS"

     # You can try frigging with modelines but use the above first
     # the 135 (dot-clock) 1280 and 1024 below are prolly right - the
     # other values you'll have to figure or experiment.  dont take this
     # example as gospel - it may not work at all on your machine!
     # Note that the modeline below is long and has wrapped
     # Modeline "1280x1024" 135 1280 1300 1612 1688 1024 1025 1028 1066 
+hsync +vsync

EndSection
------8<-------------------------------------

then you have to use the defined monitor, and specify a few alternative 
color-depths, in a new screen stanza:

------8<-------------------------------------
Section "Screen"
     Identifier "Screen Viewsonic"
     # Make sure the device matches the "Identifier" for whatever
     # the video chipset stanza defines it to be
     Device      "NV AGP"
     Monitor     "VG171b"
     DefaultColorDepth 24
     Subsection "Display"
         Depth       8
         Modes       "1280x1024" "1024x768" "800x600" "640x400"
     EndSubsection
     Subsection "Display"
         Depth       16
         Modes       "1280x1024" "1024x768" "800x600" "640x480"
     EndSubsection
     Subsection "Display"
         Depth       24
         Modes       "1280x1024" "1024x768" "800x600" "640x480"
     EndSubsection

EndSection
------8<-------------------------------------

to flip between the two screens (whatever the previous one was, and the 
new one) create or edit the "server layout" stanza (either at the very 
top or very bottom of the XF86Config-4):

------8<-------------------------------------
Section "ServerLayout"
         Identifier     "Main layout"
         Screen      0  "Screen Viewsonic" 0 0
         # Other screen entry commented out, change back to it by
         # uncommenting and restarting X.  Make sure these other
         # entries match the relevant Identifiers
         # Screen      0  "Screen0" 0 0
         InputDevice    "Keyboard0" "CoreKeyboard"
         InputDevice    "PS/2 Mouse" "CorePointer"
EndSection
------8<-------------------------------------

You can also tell X which server layout to use, so you can create two 
layout stanza's (rather than using the commenting method above) and IIRC 
use an argument to xinit, or something in .xserverrc.
Good luck!

Rgds,
-- 
Sarah Hollings                     IT Manager
sarah at humanfactors.uq.edu.au       The ARC Key Centre
Ph +61 7 33656080                  for Human Factors and
Mb +61 416 045401                  Applied Cognitive Psychology