Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!uunet!uunet!infonode!usenet
From: doyle@doyled.b23b.ingr (Doyle C. Davidson)
Newsgroups: comp.windows.x.motif
Subject: Re: writing Widgets with Float resources
Message-ID: <1991May31.135212.6584@infonode.ingr.com>
Date: 31 May 91 13:52:12 GMT
References: <13743@dog.ee.lbl.gov>
Sender: usenet@infonode.ingr.com (Usenet Administrator)
Reply-To: doyle@doyled.b23b.ingr.com
Organization: Intergraph Corporation - Third Party Software
Lines: 42

>
>I have started to write a few Motif widgets (subclassing Primitive,
>for instance), and have things working fine as long as various
>resources are "ints" (XmRInt type resources).  But I need them
>to be "floats"  (XmRFloat types).

To paraphrase "X Window System Toolit" by Asente and Swick 
(this is a great book!):

    A problem exists with storing FLOAT value into an argument list;
the C compiler will cast the FLOAT value to an integer due to
the definition of XtArgVal.  The most reliable way to do this 
is to declare a union type:
    union {
	float f;
	int   i;
    } hack;
Assign the FLOAT value to hack.f and store hack.i into the argument list.
If the resource is defined as a pointer to a FLOAT value, this problem
does not occur.  This only works if sizeof(float) == sizeof(int).

IMHO: The proper way to do PORTABLE float/double resources is to implement
them as pointer to values.  You will have to copy the value into
a private field since the resource field itself will be a pointer.

I have done this before but I backed away and used ints for my resource
value since float was overkill since screen resolution is integer based.

>	Mark Anderson

Doyle
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