# opengl-glew

Bindings to OpenGL with GLEW extension loading.

Chicken's other [opengl](http://wiki.call-cc.org/eggref/4/opengl) bindings are based on the old fixed function pipeline OpenGL. These bindings generated by [bind](http://wiki.call-cc.org/eggref/4/bind) with the OpenGL [core header file](http://www.opengl.org/registry/api/GL/glcorearb.h). Additionally, bindings to [GLEW](http://glew.sourceforge.net/) are provided for extension management.

## Installation
This repository is a [Chicken Scheme](http://call-cc.org/) egg.

It is part of the [Chicken egg index](http://wiki.call-cc.org/chicken-projects/egg-index-4.html) and can be installed with `chicken-install opengl-glew`.

## Requirements
- Make
- Bind

## Documentation
All functions and constants from the OpenGL [core header file](http://www.opengl.org/registry/api/GL/glcorearb.h) are exported. Scheme style names are provided (underscores and camelCase replaced with hyphens), the `gl` prefix is removed from names, `is` functions are given question marks, and constants are bookended by `+`s (e.g. `tex-image2d`, `enabled?`, `+arb-viewport-array+`).

### GLEW functions

    [procedure] (init)

Required to initialize GLEW/OpenGL. An OpenGL context must be created before this is called.

    [procedure] (supported? EXTENSION-NAME)

Query whether the OpenGL extension, given as a string, is supported.

### GL helper functions
    [procedure] (make-shader TYPE SOURCE)

Creates and compiles a shader object given the shader's type (e.g. `+vertex-shader+`, `+geometry-shader+`, `+fragment-shader`), and a string containing the GLSL source. Returns an integer representing the ID of the shader.

    [procedure] (make-program SHADER-LIST)

Creates and links a program object, given a list of shader objects (i.e. the integers returned by `make-shader`. Returns an integer representing the ID of the program.

    [procedure] (gen-buffer)

    [procedure] (gen-framebuffer)

    [procedure] (gen-program-pipeline)

    [procedure] (gen-query)

    [procedure] (gen-renderbuffer)

    [procedure] (gen-sampler)

    [procedure] (gen-texture)

    [procedure] (gen-transform-feedback)

    [procedure] (gen-vertex-array)

Analogous to their pluralized counterparts, but only generates and returns one (integer) object.

    [procedure] (delete-buffer BUFFER)

    [procedure] (delete-framebuffer FRAMEBUFFER)

    [procedure] (delete-program-pipeline PROGRAM-PIPELINE)

    [procedure] (delete-query QUERY)

    [procedure] (delete-renderbuffer RENDERBUFFER)

    [procedure] (delete-sampler SAMPLER)

    [procedure] (delete-texture TEXTURE)

    [procedure] (delete-transform-feedback TRANSFORM-FEEDBACK)

    [procedure] (delete-vertex-array VERTEX-ARRAY)

Analogous to their pluralized counterparts, but only accepts and deletes one (integer) object.

## Example
This example depends on the [glfw3](http://wiki.call-cc.org/eggref/4/glfw3) egg for window and context creation.

``` Scheme
(import chicken scheme)
(use (prefix glfw3 glfw:) (prefix opengl-glew gl:))

(define *vertex* 
#<<END
#version 330
in vec2 vertex;
in vec3 color;
out vec3 c;
uniform mat4 viewMatrix;

void main(){
   gl_Position = (viewMatrix * vec4(vertex, 0.0, 1.0));
   c = color;
}
END
)

(define *fragment*
#<<END
#version 330
in vec3 c;
out vec4 fragColor;
void main(){
  fragColor = vec4(c, 1.0);
}
END
)

(glfw:with-window (640 480 "Example" resizable: #f)
  ;; glfw3 automatically calls (gl:init) here when opengl-glew is loaded

  (print (gl:supported? "GL_ARB_framebuffer_object"))

  (set! *vertex* (gl:make-shader gl:+vertex-shader+ *vertex*))
  (set! *fragment* (gl:make-shader gl:+fragment-shader+ *fragment*))

  ;;If this is not zero, then everything is working:
  (print (gl:make-program (list *vertex* *fragment*))))
```

## Version history
### Version 0.3.0
* Add single element `gen` and `delete` functions

### Version 0.2.0
* Add glcorearb.h - no longer downloaded at install time

### Version 0.1.0
* Initial release

## Source repository
Source available on [GitHub](https://github.com/AlexCharlton/chicken-opengl-glew).

Bug reports and patches welcome! Bugs can be reported via GitHub or to alex.n.charlton at gmail.

## Author
Alex Charlton

## Licence
BSD