Notes to use openGL Rastersynchronization under X11 
(both Xaw and Gnome)

ATTENTION:
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To get full retro experience with synchronization to the vertrical
raster retrace messing with X11 modelines (resolution and refresh
frequencies) is necessary. 
This description is a suggestion - 
Follow this instructions at your own risk!
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The development is tested on a fairly up-to-date system (2006-12)
under Ubuntu Linux (6.10) featuring Xorg Xserver 7.1.1. and mesa
openGL including HW support (NVIDIA driver) supporting glx version 1.4
supplying GLX_SGI_video_sync.
It is assumed that this works also on other systems supporting the
required extensions.

Preconditions:
- openGl extension GLX_SGI_video_sync in your X11 setup.
  The availability of the extension is checked at startup.
  
- XRandR extension to switch proper modes (50Hz/100Hz/150Hz) is preferrable
  Proper modelines in your /etc/X11/xorg.conf must be present.
  If your systems lacks 50 or 100Hz modes you might try using
  `gtf' (typcally shipped with Xorg, xserver) - see related man page. 
  You might need to add the output such as:
    # 800x600 @ 50.00 Hz (GTF) hsync: 30.90 kHz; pclk: 31.15 MHz
    Modeline "800x600_50.00"  31.15  800 824 904 1008  600 601 604 618 -HSync +Vsync
  to you Monitor Section of /etc/X11/xorg.conf and add the resolution
  to the `Screen' section.

  Sometimes some consistency checks within the display driver drop
  this resolutions again.
  To drop e.g. the autodetection features in the NVIDIA driver you
  might add `Option "UseEDID" "FALSE"' in section `Device'. 

  ATTENTION: Disabling such features might allow X11 to access your HW
  in a way that it gets damaged! You are at your own risk!

Usage: 
Enable fullscreen (not necessary, but makes sense):
- choose your preferred resolution/refresh XRandR Resolutions and 
  enable XRandR as fullscreen device
- Activate fullscreen with `Alt-D'.

- choose `OpenGL Rastersynchronization' in the
  video chip menu (VIC-II Settings, VIC Setting, etc.)
- to get synchronized video output even on a non-aligned frequency
  (e.g. when you cannot install a proper modeline supporting a 50 or
  100Hz frequency) then try:
  - disable sound output
  - set refresh rate to 1/1
  - set max speed to `no limit'.
  of course emulation speed then is driven by the video refresh rate
  (and might be significant faster) and sound output is disabled. 

Todo:
- integrate in vsync properly
- Decide whether to drop non-aligned frequencies (i.e. not multiple of
  50Hz)
- fix Xaw fullscreen enabling.
- introduce in other emulators (not only x64).
- handle double size fullscreen mode
