Conference bulova::decw_jan-89_to_nov-90

    The type should be obvious from module DWT, in file
    SYS$LIBRARY:DECW$DWT_.ADA, and the Ada compiler should also have listed
    the type it was expecting when it tried to find a DWT$FETCH_SET_VALUES
    procedure whose signature matched the actuals.  The Ada compiler
    generates very helpful error messages, containing a lot of information.
    It's worth reading them.
    
    
    From SYS$LIBRARY:DECW$DWT_.ADA:
    
    procedure FETCH_SET_VALUES (
	STATUS		: out CARDINAL_TYPE;			-- return value
	HIERARCHY_ID	: in  DRM_HIERARCHY_TYPE;
	WIDGET		: in  WIDGET_TYPE;
	ARGS		: in  ARG_ARRAY_TYPE;
	NUM_ARGS	: in  CARDINAL_TYPE);
 
    ARGS is an ARG_ARRAY_TYPE, which is defined as follows:
    
    type ARG_ARRAY_TYPE is array (NATURAL range <>) of ARG_TYPE;
    
    where
    
    type ARG_TYPE is
	record
	    ARG_NAME	: STRNG_TYPE;				--  ptr to actual chars 
	    ARG_VALUE	: ARG_VAL_TYPE;				--  index into arglist
	end record;
    
    So your user needs an array of ARG_TYPEs, not a single one.
    
    John

Re .1

>    type ARG_TYPE is
>        record
>            ARG_NAME    : STRNG_TYPE;		--  ptr to actual chars 
>            ARG_VALUE   : ARG_VAL_TYPE;        --  index into arglist
>        end record;
>    

I guess the question should be restated in that how do you specify items
for the ARG_VALUE field of the ARG_TYPE record.  On page 4-16 of the
DECwindows Programming, Vol II of Toolkit Routines in the chapter on
DRM routines, they show an example (in C) of how to specify the name
and value part of the arglist.  They show:

	args[n].name = "label"
	args[n].value = "OK_button_label"

Now, the problem is when you look at what ARG_VAL_TYPE is it is defined to
be   (from SYS$LIBRARY:DECW$DWT_.ADA):
-- System Dependent Definitions
--
--
-- XtArgVal ought to be a union of caddr_t, char *, long, int *, and proc *
-- but casting to union types is not really supported.
--
-- So the typedef for XtArgVal should be chosen such that
--
--      sizeof (XtArgVal) >=    sizeof(caddr_t)
--                              sizeof(char *)
--                              sizeof(long)
--                              sizeof(int *)
--                              sizeof(proc *)
--
-- ArgLists rely heavily on the above typedef.
--
--***************************************************************
    subtype ARG_VAL_TYPE is INTEGER;

When he tries to assign a string to that item of the arglist, he gets a
compiler error.  Is he supposed to pass a ptr to the string? That is what
C does...  Or are the bindings in error?

Rick Beldin

You need to assign the address of a null-terminated string to the VALUE
field of the array element.  STRNG_TYPE is a subtype of SYSTEM.ADDRESS.

The DECBURGER and HELLOWORLD Ada examples have lots of uses of this type
of construct, though FETCH_SET_VALUES isn't used directly in either one.

				Steve

    You're better off using the convenience routines to get inside an
    ARG_ARRAY_TYPE value:
    
    declare
    	arglist : dwt.arg_array_type(0..0);
    	label : constant string:= "OK_button_label" & ascii.nul;
    begin
    	-- Put some values into the argument list
    	dwt.vms_set_arg(label'address,
    		        arglist,
    		        0,
    		        dwt.C_label);
    
    	-- Use arglist is a DWT.xxxxxx call
    
    	-- Then free any storage allocated by VMS_SET_ARG
    	for i in arglist'range loop
    	    dwt.vms_free_argnames(arglist,i);
    	    -- Free the storage allocated by VMS_SET_ARG for the
    	    -- copy it makes of the argument name
    	end loop;
    end;		
    
    There is a convenience routine called VMS_SET_DESC_ARG, which is
    supposed to stuff a string directly into an ARG_ARRAY_TYPE (so you
    don't have to declare a constant null-terminated string and get the
    address of it), but I don't see how you're supposed to free up the
    temporary storage that that will allocate (unless VMS_FREE_ARGNAMES
    is very clever, which I doubt).  Maybe the documentation fo V5.3 is
    clearer on this point?
    
    John
    

VMS_FREE_ARGNAMES is indeed what you use to free the storage allocated
by VMS_SET_DESC_ARG.

			Steve