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<TITLE>PROGRAMMING TIPS</TITLE>
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Programming Tips
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This is a start at a list of programming tips for Motif - not LessTif specific.
It's not intended to be a comprehensive guide, but rather a collection
of useful techniques that are often overlooked and can really speed Motif
development and execution of Motif programs.
<P>
Since it's so short at the moment, there's not much in the way of overall
organization, but as the list grows, we'll fix that.
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<OL>
<LI>
<BIG>What's the preferred way to specify arguments (i.e. XtSetArg, etc)?</BIG>
<BR>
There are two answers to this question depending on if the resources
actually need to be specified before/during creation, or if they can be
specified after creation.
For resources which must be set prior to creation, the preferred method is
this:
<PRE>
int n;
Arg args[10];
Widget button;
n=0;
XtSetArg(args[n], XmNx, 100); n++;
XtSetArg(args[n], XmNy, 120); n++;
button = XmCreatePushButton(parent, "Button", args, n);
</PRE>
The advantage of this is that you don't have to keep count of the
arguments yourself, which is prone to error. Note that you can't use
args[n++] because this is a macro which will be expanded to have more than
one n++ in it. A disadvantage to this is that you may overflow your
static args array if you add to many args. Fortunately, when this happens
it almost always causes immediate problems (i.e. a core dump) which means
that the error will usually be caught fairly quickly.
For resources which may be set after creation, the preferred method as
follows:
<PRE>
button = XmCreatePushButton(parent, "Button", NULL, 0);
XtVaSetValues(button,
XmNx, 100,
XmNy, 120,
NULL);
</PRE>
This eliminates any possibility of overflowing the Arg array, and is
easier to type and read anyway. This method should be used for all
resources except those which must be set during widget creation.
<P>
<LI>
<BIG>When should widgets be managed?</BIG><BR>
Manager widgets should not be managed until *after* all the children are
added. This is because geometry calculations are expensive operations
(timewise) and if the manager widget is managed it must re-negotiate the
geometry of all its children after each new child is added, instead of
doing it only once after all children are added.
</OL>
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