[vox-tech] Changing Debian Screen Resolution

[Karsten M. Self]

Ken:

on Thu, Mar 03, 2005 at 10:53:50PM -0800, Robert G. Scofield (rscofield at afes.com) wrote:
> On Thursday 03 March 2005 17:33, Ken Bloom wrote:
> >
> >
> > Edit your /etc/X11/XF86Config-4
> > find
> > Section "Screen"
> > then find the Subsection "Display" which corresponds to the default
> > color depth. Add "1024x768" at the beginning of the Modes line.

First:  my usual suggestion is to go through the configuration tool
rather than edit the file directly.  No real harm, either way, but once
you modify a conffile in Debian, automated updates _won't_ touch it.  A
set of MD5 hashes is kept by the system, for XF86 it's /var/lib/xfree86/

The "debian way" here is:

    $ sudo dpkg-reconfigure xserver-xfree86

...you'll be walked through the setup screens, with your prior settings
preselected.

If you have modified the file, delete/move both it and the MD5sums.


> Believe it or not, the solution does not work.  I ended up modifying the 
> resolution for all color depth entries.  I added 1024x768 and removed all 
> other resolutions.  Here's what happens when I reboot.

Note that your *default* color depth is the only one that's tried, so
other CDs may not apply.

You can test color depths when manally starting X with the '-bpp'
option:

    $ startx < client arguments > -- -bpp <depth> < server arguments >

startx (a wrapper for launching X) allows specifying both client
arguments (the programs that run under X) and server args (options for
the server).  Typically your client args are your window manager or
desktop, e.g.:  blackbox, gnome-session, wmaker, twm.
 
> When X starts the bottom one fifth of the screen becomes a black band.
> The the screen blinks, and you see a small mouse pointer indicating
> that the resolution is 1024x768.  But then the screen blinks again and
> the mouse arrow is big indicating that I'm back at 800x600.  GNOME
> continues to boot, and there I am in 800x600.

OK.

There's several ways X won't fire up:

  - If your _monitor_ can't handle the mode you've given it, you'll
    frequently get some sort of "out of scan range" or similar message,
    as a dialog, on the monitor itself.  This isn't your OS telling you
    something, it's the monitor's own firmware.  This is a safety
    feature.  In days of yore, the magic smoke could escape.  For any
    monitor produced since ~1995, a safety circuit will prevent this.

  - When you configure X (via XF86Config(-4)), the questions about your
    monitor capabilities, and the section labled "Monitor", define what
    *X* thinks your monitor's capabilities are.  X itself will bail on
    any modes which it thinks your monitor can't handle.  Sometimes your
    monitor *is* physically capable of running higher modes.  In this
    case, either gritting your teeth and lying ("it says 1024x768 @ 85
    Hz 32 bpp but I know it will do 1280x960 at 75 24bpp"), or even
    generating your own modeline (the line labled "Modeline" in your
    XF86Config file) will buy you higher resolution, better color depth,
    higher refresh, and/or all of the above.  While modeline editing is
    not generally required, you _can_ find modeline generators both
    online and in some distros (in Debian:  'modeline' and 'videogen'
    packages).

  - Your display mode is a factor of your video card's speed and memory,
    your monitor's capabilities, and your own specifications of
    resolution, color depth, and refresh rate.  Any time I have trouble
    getting the mode I *want* configured, I try to fall back to
    something really vanilla:  800x600 at 60Hz & 8bpp.  Resolution,
    refresh, and color depth can all have a big impact.  I'm setting up
    system with an oldish S3 card which refused to run at any depth
    greater than 16, FWIW.

 
> Now here's another mystery.  When I type "xandr" I'm given about 4 screen 
> resolutions.  This is interesting since XFConfig-4 has only one; 1024x768.  
> What's more xandr has an asterisk indicating that my resolution is set at 
> 800x600.

I'm not familiar with xandr.

There's a newish generation of interactive X resolution switchers which
may possibly bypass what's in your config file -- X has its own built-in
knowledge of resolutions and capabilities.

 
> I'm wondering if something is overriding XF86Config-4.  Could GDM be doing 
> something?   

Not likely.

> Here's another thought.  You might remember several weeks ago when I
> was trying to set up X.  I was trying to follow the directions for an
> outdated version of X.  I'm wondering if I may have set up another
> configuration file like you used to do before Linux started using
> XFConfig-4.

No.  Your X server will use only one config file.  You can verify which
in /var/log/XFree86.<displaynumber>.log

Display number is typically '0' (number zero, not letter oh).
 
> Does anybody have any thoughts about this?  In the meantime I'll start
> looking for another configuration file that I may have set up.

Um.  I think you're in the right place, see above.


Peace.

-- 
Karsten M. Self <kmself at ix.netcom.com>        http://kmself.home.netcom.com/
 What Part of "Gestalt" don't you understand?
    So don't deal with it.  Don't use software that uses it.
    - Jeff Waugh, offering preferred GNOME usability workaround.
       http://zgp.org/pipermail/linux-elitists/2004-January/008588.html

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