Question:                                           21th July 98
      If we:
       - run tcltkgrass
       - run d.mon x0

      we get the following error:
	"cannot allocate any read/write color cells"
      How to fix that?

Answer:
This error is related to 8bit-displays only.

Common fault is to start "Netscape" before using GRASS. That
MUST be avoided! Netscape grabs all colors and does not
allow GRASS to get 256 colors at least.

Two things have to be done (usually you should be able to
run your Xserver at least with 15bit):

1. Set a better color depth (more than 8bit):

    1.a) If the file .xserverrc is NOT existing in your home directory

        - create .xserverrc in your home directory
   
        (create this file with a text editor in your home directory 
         with starting dot.)

        - Contents of the file:
          exec X :0 -bpp 32 $*
    
       If you have limited RAM on your graphics card, use -bpp 24 or
       -bpp 16 instead. Existing limitation you will realize through
       a loss in screen resolution.

       - Ready.

       If the Xserver does not start, then use the following line 
       instead (you may choose another color depth):

          exec X :0 -auth .Xauthority -bpp 32 $*

    1.b) If the file .xserverrc IS existing in your home directory

        - At the end of this file you will find one or two line(s) 
          containing "X :0". It may look like this: 

          Example:
                exec X :0 -auth .Xauthority $*
            else
                exec X :0 $*
            fi

        - Force the color depth of the Xserver there (set option -bpp 32):

          Example:
                exec X :0 -auth .Xauthority -bpp 32 $*
            else
                exec X :0 -bpp 32 $*
            fi


        - Ready.

 Now the Server will get into the 16.7 million color mode.
 Again: If you have to less memory on your graphic card, the screen 
 resolution might become bad. In this case you might use -bpp 16 
 (65536 colors) or -bpp 24 (packed true color) instead.


2. Only, if you insist using 8bit Xserver:
   Be careful with starting color consuming applications before
   starting a GRASS monitor:

    - never start "Netscape" and/or "xv" before starting a
      GRASS monitor with d.mon. These applications are well known
      in GRASS community to cause white screens etc. in GRASS
      monitor while displaying data.

    - start Netscape after starting a GRASS monitor
      (maybe use -install option to install a private colormap
       for this netscape session)

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3.  If the problem is not yet fixed, check if there are other
   color consuming applications (also funny colored icons on the
   desktop etc.). Use color reduced icons in this case. 

Markus Neteler
July 1998