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glium 0.17.1

Elegant and safe OpenGL wrapper. Glium is an intermediate layer between OpenGL and your application. You still need to manually handle the graphics pipeline, but without having to use OpenGL's old and error-prone API. Its objectives: - Be safe to use. Many aspects of OpenGL that can trigger a crash if misused are automatically handled by glium. - Provide an API that enforces good pratices such as RAII or stateless function calls. - Be compatible with all OpenGL versions that support shaders, providing unified API when things diverge. - Avoid all OpenGL errors beforehand. - Produce optimized OpenGL function calls, and allow the user to easily use modern OpenGL techniques.
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use DrawError;

use uniforms::SamplerBehavior;

use gl;
use context::CommandContext;
use version::Version;
use version::Api;
use GlObject;
use ToGlEnum;

/// An OpenGL sampler object.
pub struct SamplerObject {
    id: gl::types::GLuint,
    destroyed: bool,
}

impl SamplerObject {
    /// Builds a new sampler object.
    pub fn new(ctxt: &mut CommandContext, behavior: &SamplerBehavior) -> SamplerObject {
        // making sure that the backend supports samplers
        assert!(ctxt.version >= &Version(Api::Gl, 3, 2) ||
                ctxt.version >= &Version(Api::GlEs, 3, 0) ||
                ctxt.extensions.gl_arb_sampler_objects);

        let sampler = unsafe {
            use std::mem;
            let mut sampler: gl::types::GLuint = mem::uninitialized();
            ctxt.gl.GenSamplers(1, &mut sampler);
            sampler
        };

        unsafe {
            ctxt.gl.SamplerParameteri(sampler, gl::TEXTURE_WRAP_S,
                                      behavior.wrap_function.0.to_glenum() as gl::types::GLint);
            ctxt.gl.SamplerParameteri(sampler, gl::TEXTURE_WRAP_T,
                                      behavior.wrap_function.1.to_glenum() as gl::types::GLint);
            ctxt.gl.SamplerParameteri(sampler, gl::TEXTURE_WRAP_R,
                                      behavior.wrap_function.2.to_glenum() as gl::types::GLint);
            ctxt.gl.SamplerParameteri(sampler, gl::TEXTURE_MIN_FILTER,
                                      behavior.minify_filter.to_glenum() as gl::types::GLint);
            ctxt.gl.SamplerParameteri(sampler, gl::TEXTURE_MAG_FILTER,
                                      behavior.magnify_filter.to_glenum() as gl::types::GLint);

            if let Some(max_value) = ctxt.capabilities.max_texture_max_anisotropy {
                let value = if behavior.max_anisotropy as f32 > max_value {
                    max_value
                } else {
                    behavior.max_anisotropy as f32
                };

                ctxt.gl.SamplerParameterf(sampler, gl::TEXTURE_MAX_ANISOTROPY_EXT, value);
            }
        }

        SamplerObject {
            id: sampler,
            destroyed: false,
        }
    }

    ///
    #[inline]
    pub fn destroy(mut self, ctxt: &mut CommandContext) {
        self.destroyed = true;

        unsafe {
            ctxt.gl.DeleteSamplers(1, [self.id].as_ptr());
        }
    }
}

impl GlObject for SamplerObject {
    type Id = gl::types::GLuint;

    #[inline]
    fn get_id(&self) -> gl::types::GLuint {
        self.id
    }
}

impl Drop for SamplerObject {
    #[inline]
    fn drop(&mut self) {
        assert!(self.destroyed);
    }
}

/// Returns the sampler corresponding to the given behavior, or a draw error if
/// samplers are not supported.
pub fn get_sampler(ctxt: &mut CommandContext, behavior: &SamplerBehavior)
                   -> Result<gl::types::GLuint, DrawError>
{
    // checking for compatibility
    if ctxt.version < &Version(Api::Gl, 3, 2) && !ctxt.extensions.gl_arb_sampler_objects {
        return Err(DrawError::SamplersNotSupported);
    }

    // looking for an existing sampler
    match ctxt.samplers.get(behavior) {
        Some(obj) => return Ok(obj.get_id()),
        None => ()
    };

    // builds a new sampler
    let sampler = SamplerObject::new(ctxt, behavior);
    let id = sampler.get_id();
    ctxt.samplers.insert(behavior.clone(), sampler);
    Ok(id)
}