Path: utzoo!attcan!uunet!lll-winken!ames!elan!jlo
From: jlo@elan.UUCP (Jeff Lo)
Newsgroups: comp.windows.x
Subject: Re: visual depth vs. colormap_size
Message-ID: <503@elan.UUCP>
Date: 5 Apr 89 16:56:01 GMT
References: <978@quintus.UUCP>
Reply-To: jlo@elan.UUCP (Jeff Lo)
Organization: Elan Computer Group, Inc., Mountain View, CA
Lines: 32

In article <978@quintus.UUCP> pds@quintus.UUCP (Peter Schachte) writes:
>The XVisualInfo structure has two members that appear to be redundant,
>namely depth and colormap_size.  In every case I've seen, which isn't
>many, colormap_size == 1<<depth.  I don't see why this wouldn't always
>be the case, but I'm not sure.  So the question is:  is this relationship
>always the case?  If not, how can this happen?
>
>Thanks in advance,
>-- 
>-Peter Schachte
>pds@quintus.uucp
>...!sun!quintus!pds

What you are seeing is not always the case.  We have an HP 9000/320 with
an older mono display card, running HP's X11R2 server.  With this card the
display has a depth of 8, but only 2 colormap cells.  I have heard that it
is something needing compatibility with older color cards which are byte
per pixel addressed, so the mono board was addressed with one byte per pixel.
This is from xdpyinfo:

  depth of root window:    8 planes
  number of colormaps:    minimum 1, maximum 1
  default colormap:    0x80065
  default number of colormap cells:    2
  preallocated pixels:    black 0, white 1

Strange but true...
-- 
Jeff Lo
..!{ames,uunet}!elan!jlo
Elan Computer Group, Inc.
415-964-2200