Re: How to get the mouse position with JEWL?

[Jeffrey Carter <spam.jrcarter.not@spam.not.acm.org>]

On 10/20/2010 03:51 PM, tmoran@acm.org wrote:
> This works for me for Windows
>      type Points is record
>        x,y : interfaces.c.int;
>      end record;

I'd add

pragma Convention (C, Points);

just to be safe.

>      type bool is new interfaces.c.int;
>      function GetCursorPos(point : access points) return bool;

(Point : in Points)

should work just as well, and has the advantages that

>      pragma import(stdcall,GetCursorPos, "GetCursorPos");
>      current : aliased points;

you don't need "aliased"

>      ...
>        if getcursorpos(current'access) = 0 then

and you don't need 'access.

This works because of ARM B.3: "An Ada parameter of a record type T, of any 
mode, other than an in parameter of a type of convention C_Pass_By_Copy, is 
passed as a t* argument to a C function, where t is the C struct corresponding 
to the Ada type T."

It is a little confusing because an "in" parameter is modified.

-- 
Jeff Carter
"You empty-headed animal-food-trough wiper."
Monty Python & the Holy Grail
04