Re: Function set-gl-vertex-array in Guile-opengl

[Daniel Llorens <daniel.llorens@bluewin.ch>]

Hi Luis, 

I don't really have an answer to your question, but I wanted to point out that Guile already has make-f32vector, f32vector-set!, etc. You don't need to define your own. IMO it's not a good idea to use bytevector-xxx-set!/ref to operate on typed vectors unless you are type punning.

The make-f32vector, etc. functions are in SRFI-4, they aren't specific to Guile.

PS I didn't understand the purpose of (* n 30) on your code. The original you link has (* n 4) which is what I'd expect for f32.

Regards

	Daniel


> From: Luis Souto Graña <luissoutobueu@gmail.com>
> Subject: Function set-gl-vertex-array in Guile-opengl
> Date: 25 January 2019 at 11:36:33 CET
> To: guile-user@gnu.org
> 
> 
> Hello, I'm trying to use the function set-gl-vertex-array in Guile-opengl .
> It needs a bytevector as an argument. I wrote this doing a copy-paste from
> here: https://github.com/marcomaggi/vicare/blob/master/attic/lab/gears.scm
> 
> (use-modules (rnrs bytevectors))
> (use-modules (system foreign))
> 
> (define (f32vector . lst)
>  (define-syntax f32set!
>    (syntax-rules ()
>      ((_ bv n value)
>       (bytevector-ieee-single-native-set! bv (* n 30) value))))
>  (let ((bv (make-bytevector (* (length lst) 30))))
>    (let loop ((i 0) (lst lst))
>      (cond ((null? lst) bv)
>        (else
>         (f32set! bv i (car lst))
>         (loop (+ i 1) (cdr lst)))))))
> 
> (define points (f32vector 30.0 30.0 0.0
>                      10.0 10.0 0.0
>                      70.0 30.0 0.0
>                      90.0 10.0 0.0
>                      70.0 70.0 0.0
>                      90.0 90.0 0.0
>                      30.0 70.0 0.0
>                      10.0 90.0 0.0
>                      30.0 30.0 0.0
>                      10.0 10.0 0.0))
> 
>> points
> #vu8(0 0 240 65 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 240
> .....
> 
>> (bytevector-length points)
> 900
> 
>> (bytevector->pointer points)
> #<pointer 0x56090d909aa0>
> 
> 
> So, it works well.
> 
> Now, if I write:
> 
> (use-modules (gl) (glut))
> 
>> ,apropos set-gl-vertex-array
> (gl): set-gl-vertex-array    #<procedure set-gl-vertex-array (type
> bv-or-pointer #:optional size #:key stride offset)>
> 
> 
>> (set-gl-vertex-array (bytevector->pointer points) 3)
> 
> ERROR: In procedure scm-error:
> unhandled array-pointer type 3
> 
> Can someone tell me what the solution is?
> 
> 
> 
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