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From: chucko@ucscc.UCSC.EDU (30502000)
Newsgroups: comp.windows.x.motif
Subject: Writing Motif widgets
Message-ID: <8938@darkstar.ucsc.edu>
Date: 14 Nov 90 16:19:10 GMT
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Organization: University of California, Santa Cruz  CATS
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creating new widgets for the OSF/Motif Toolkit

1.  Has anyone written a widget that builds on the Motif widget
    hierarchy?

2.  How is this done?  Usually users do not have source code for the
    Motif widget set.  The system libraries only contain include files.
    We notice Athena widgets connect the widget inheritance hierarchy
    by including the ancestor's --P.h file in the child's --P.h file.
    In Motif, however, --P.h files do not do this.  Perhaps they did
    this in the --.c file, but when We tried that it led to another
    problem (below).

Problem:
I worked through some examples in Volume 4 of O'Reilly & Assoc.
and I was successful at creating a child widget in the Simple,
Label, Command hierarchy.  However, we are using the Motif toolkit
so we would like any widgets we add to have the Motif look and feel.

I attempted to clone a (Motif) widget under the pushbutton using
HPs X11 V3 and their version of Motif (an incomplete 1.0 i think).  
I started with  PushB.h and  PushBP.h and a .c file i copied from 
a model in Volume 4 of O'Reilly & Assoc.   

I did not modify the .h files. I included XmP.h and PushBP.h in the .c
file.  I modified the .c file as follows:
------------------------------
#define SuperClass ((xmLabelWidgetClass) &xmLabelClassRec)
XmPushButtonClassRec xmPushButtonClassRec = {
  {
    (WidgetClass) SuperClass,		/* superclass		  */	
    "XmPushButton",			/* class_name		  */
    sizeof(XmPushButtonRec),		/* size			  */
    NULL,				/* class_initialize	  */
    .
    .
  }
  /* for public consumption */
WidgetClass xmPushButtonWidgetClass = (WidgetClass) &xmPushButtonClassRec;
------------------------------

I got the following compile errors:

cc: "PushBP.h", line 63: error 1000: Unexpected symbol: "XmLabelClassPart".
cc: "PushBP.h", line 68: error 1000: Unexpected symbol: "xmPushButtonClassRec".
cc: "PushBP.h", line 98: error 1000: Unexpected symbol: "XmLabelPart".
cc: "PushB.c", line 64: error 1000: Unexpected symbol: "xmPushButtonClassRec".

If I include LabelP.h in the .c file I get the following compile 
errors:

cc: "PushB.c", line 64: error 1603: Incompatible operands: & operator.
cc: "PushB.c", line 64: error 1527: Incompatible types in cast.
cc: "PushB.c", line 64: error 1521: Incorrect initialization.
 
 The line 64 is:
    (WidgetClass) SuperClass,		/* superclass		  */	
    (in class structure)

Any clues?

Sincerely,
Stuck in Monterey with the widget blues again.

Charles Stein & Christina Shaw 
Naval Oceanographic & Atmospheric Research Lab.

noarlw\!stein@uunet.uu.net   -or-   chucko@ucscc.ucsc.edu