I am trying to create some types/procs to be able to use OpenGL functionality
in Nim. I started with the Opengl Program object. I created a proc that
compiles a vertex and fragment shader, then links it into a program and stores
the id in the Program object. This works.
But to perform some error checking (checking errors in shader code or in
linker), you need to pass a pre-allocated cstring to a function. I don't know
how to do that and I don't seem to be able to find it in the manual. I tried
several things, and the last one was creating a sequence of chars and passing
the addr but it doesn't work.
How do you do this?
Here's a part the code:
import opengl
type
openglProgram = object
id: GLuint
...
proc createOpenglProgram(vert: string, frag: string) : openglProgram =
result.id = glCreateProgram()
var status: GLint
let vs = glCreateShader(GL_VERTEX_SHADER)
let verts = allocCStringArray([ vert ])
glShaderSource(vs, 1.GLsizei, verts, nil)
glCompileShader(vs)
glGetShaderiv(vs, GL_COMPILE_STATUS, status.addr)
if status != GL_TRUE.GLint:
var length: GLint
glGetShaderiv(vs, GL_INFO_LOG_LENGTH, length.addr)
var msg = cstring # <= this is the one that should be preallocated to
be of size 'length'
glGetShaderInfoLog(vs, length, nil, msg) # <= this gives error because
msg is a null pointer
echo "Error in vertex shader: " & $msg
glAttachShader(result.id, vs);
...
Run
How?
Also: coding this is really a pain, it's ugly, and gives me a headache... I
don't mind doing it once because after that, this code is never to be touched
again, but if there is a way to do it better than this, please let me know. I'm
still very new to Nim.
Also: when passing the cStringArray (in earlier call glShaderSource), I need to
pass the size of that array. I _know_ it is 1 so I hard code it, but is there a
way to get the size from the cStringArray?
