Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!bloom-beacon!EXPO.LCS.MIT.EDU!jim
From: jim@EXPO.LCS.MIT.EDU (Jim Fulton)
Newsgroups: comp.windows.x
Subject: Re: Resource Database - Help!
Message-ID: <8805131605.AA20134@EXPO.LCS.MIT.EDU>
Date: 13 May 88 16:05:26 GMT
References: <1610015@hpcvlx.HP.COM>
Sender: daemon@bloom-beacon.MIT.EDU
Organization: X Consortium, MIT Laboratory for Computer Science
Lines: 79


More complete explanations can be found in the "Using and Specifying X
Resources" tutorial that was sent out a couple months ago and will be a part of
R3.  I'll mail a copy of it to you separately.  However, for the sake of 
discussion,


> 1.  Who owns a resource database?  A client?  A window?  

A client.


> 2.  There are specific references to a resource database loaded into the
>     server, or stored as a property on the root window.  Which is true?

Resources are obtained from the following places:

        1. from the RESOURCE_MANAGER property on the root window of screen 0;
           these are stored using the xrdb program.  If this property is not
           defined, then $HOME/.Xdefaults will be read to provide compatibility
           with X10 (although the resource specification format has
           changed somewhat).

        2. from any application-specific resource files, usually stored in
           /usr/lib/X11/app-defaults/.

        3. from any user-specific defaults stored in a file whose name is set
           in the environment variable XENVIRONMENT.

        4. from the -xrm command line option (for programs written with the
           X Toolkit).


> 3.  What does the first quote above mean by "when you log in"?  Does that
>     mean when you fire up the X server?  Or does it mean when you open 
>     a display?

It actually means when you run a program like xrdb that sets the
RESOURCE_MANAGER property on the root window of screen 0.  You do this from
whatever mechanism you use to start up your commonly-used X applications (e.g.
your window manager, terminal emulators, clocks, load average monitors,
editors, mail readers, etc.).  I use a little shell script, other people have
fancy session managers, etc.  An example is given in the Resources Tutorial,
but it boils down to running the xrdb program.


> 5.  Is the resouce database and the resource manager referred to in the 
>     Xlib manual the same as that used by the toolkit?

Yes.


> 6.  In section 10.11.2 of the Xlib manual, it says that a resource
>     database is an opaque type.  What does this mean?  

An XrmDatabase is defined as:

	typedef struct _XrmHashBucketRec *XrmDatabase;

However, if you look around, you'll find that there is no definition
for struct _XrmHashBucketRec in the public include files.  As a result,
your program cannot access any fields in it; this is a useful way to do
abstraction and data hiding.


> 7.  Section 4 of the Inter-client Communication Conventions Manual
>     discusses resources that are allocated to clients.  Are these the
>     same types of resouces as are discussed in the Xlib manual, chapter 10?

Yes.

A copy of "Using and Specifying X Resources" will arrive separately.


					Jim Fulton
					X Consortium
					MIT Laboratory for Computer Science 
					(617) 253-1428
					jim@EXPO.LCS.MIT.EDU