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From: aw@jello.bae.bellcore.com (Andrew Wason)
Newsgroups: comp.windows.x
Subject: Re: xrdb
Message-ID: <1991Apr11.231801.5825@bellcore.bellcore.com>
Date: 11 Apr 91 23:18:01 GMT
References: <14315@hacgate.UUCP>
Sender: usenet@bellcore.bellcore.com (Poster of News)
Reply-To: aw@bae.bellcore.com
Distribution: na
Organization: Bell Communications Research
Lines: 54

In article <14315@hacgate.UUCP>, sean@hazel.eos.scg.hac.com writes:
>If I want to run a client on a Sun and a Mac, and be able to have seperate
>width, height, and font resources for both machines, how do I go about
>specifying this with xrdb?  Is it based on the current DISPLAY value?  What
>if they specify the display value on the command line of an application?

It is based on the server xrdb used when it was run.

>How does xrdb know when to use resources speicified for the Mac and resources
>speicified for the Sun?

xrdb runs its input through cpp.  It also defines some
symbols based on the server it was run on.  These are
HOST, WIDTH, HEIGHT, X_RESOLUTION, Y_RESOLUTION, PLANES, BITS_PER_RGB,
CLASS and COLOR (see xrdb(1) for explanations of these).

So you can have one file which you can set up to work
correctly for certain types of servers by #ifdefing
chunks of resources.

For example, in the resources I feed to xrdb, I put
an '#ifdef COLOR' around all color resources.  So when I
run xrdb on my color server, I get all my color resources.
But when I run xrdb on my monochrome server, no color resources
are loaded and so everything defaults correctly.
e.g.

  #ifdef COLOR
  XBiff*background:       gray
  XBiff*foreground:       yellow
  #endif
  XBiff*update:           5
  XBiff*volume:           15

You could also use the WIDTH and HEIGHT symbols
to conditionally include geometry resources depending
on the size of your screen e.g.:

  #if WIDTH > 1000
  XBiff.width:    512
  #else
  XBiff.width:    256
  #endif

Type 'xrdb -symbols' to see the symbols defined for a particular server.
Type 'xrdb -query' to see the resources xrdb actually loaded.

Andrew

_______________________________________________________________________________

Andrew Wason                                       Bell Communications Research
aw@bae.bellcore.com                                Piscataway, NJ
bellcore!bae!aw