vlang

What is the variable `C` in some modules in vlib?

I was trying to figure out how to use the image library in vlib, in which there was a variable C:

pub fn (img Image) tex_image_2d() {
    mut rgb_flag := GL_RGB
    if img.ext == 'png' {
        rgb_flag = GL_RGBA
    }
    C.glTexImage2D(GL_TEXTURE_2D, 0, rgb_flag, img.width, 
        img.height, 0, rgb_flag, GL_UNSIGNED_BYTE, img.data)
}

On the 6th line the function calls a method that belongs to the variable C. What kind of object is C, and where could I find the source code for it?

Thanks in advance!

Solution

  • It's a C function call from imported #include "stb_image.h"

    See the code here for example