surfman 0.3.0

A cross-platform, low-level toolkit for GPU surface management
Documentation 
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// surfman/surfman/src/gl_utils.rs
//
//! Various OpenGL utilities used by the different backends.

use crate::Gl;
use crate::gl::types::{GLenum, GLint, GLuint};
use crate::gl;

#[allow(dead_code)]
pub(crate) fn create_and_bind_framebuffer(gl: &Gl, texture_target: GLenum, texture_object: GLuint)
                                          -> GLuint {
    unsafe {
        let mut framebuffer_object = 0;
        gl.GenFramebuffers(1, &mut framebuffer_object);
        gl.BindFramebuffer(gl::FRAMEBUFFER, framebuffer_object);
        gl.FramebufferTexture2D(gl::FRAMEBUFFER,
                                gl::COLOR_ATTACHMENT0,
                                texture_target,
                                texture_object,
                                0);
        framebuffer_object
    }
}

pub(crate) fn unbind_framebuffer_if_necessary(gl: &Gl, framebuffer_object: GLuint) {
    unsafe {
        // Unbind the framebuffer if it's bound.
        let (mut current_draw_framebuffer, mut current_read_framebuffer) = (0, 0);
        gl.GetIntegerv(gl::DRAW_FRAMEBUFFER_BINDING, &mut current_draw_framebuffer);
        gl.GetIntegerv(gl::READ_FRAMEBUFFER_BINDING, &mut current_read_framebuffer);
        if current_draw_framebuffer == framebuffer_object as GLint {
            gl.BindFramebuffer(gl::DRAW_FRAMEBUFFER, 0);
        }
        if current_read_framebuffer == framebuffer_object as GLint {
            gl.BindFramebuffer(gl::READ_FRAMEBUFFER, 0);
        }
    }
}

#[allow(dead_code)]
pub(crate) fn destroy_framebuffer(gl: &Gl, framebuffer_object: GLuint) {
    unbind_framebuffer_if_necessary(gl, framebuffer_object);
    unsafe {
        gl.DeleteFramebuffers(1, &framebuffer_object);
    }
}