glium 0.36.0

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.
Documentation 
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//! Image units, views into specific planes of textures
use crate::ToGlEnum;
use crate::gl;
use crate::texture;
use crate::texture::GetFormatError;

#[derive(Debug)]
/// Represents an error related to the use of an Image Unit
pub enum ImageUnitError {
    /// The texture does not contain a mipmap at the requested level
    NoMipmapAtLevel(u32),
    /// This type of texture is not layered
    LayeringNotSupported(texture::Dimensions),
    /// The layer requested is out of the bounds of this texture
    LayerOutOfBounds(u32),
    /// The format of the texture and the requested format are not compatible
    BadFormatClass(usize, usize),
    /// Error while trying to get the format of the passed texture
    GetFormat(GetFormatError),
}

impl std::fmt::Display for ImageUnitError {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        use self::ImageUnitError::*;

        let desc = match *self {
            NoMipmapAtLevel(level) => write!(f, "No mipmap level {} found", level),
            LayeringNotSupported(kind) => write!(f, "Layering is not supported with textures of dimensions {:?}", kind),
            LayerOutOfBounds(layer) => write!(f, "Request layer {} is out of bounds", layer),
            BadFormatClass(tbits, ibits) => write!(f, "Texture format has {} bits but image format has {} bits", tbits, ibits),
            GetFormat(error) => write!(f, "{}", error),
        };
        Ok(())
    }
}

impl std::error::Error for ImageUnitError {}


/// How we bind a texture to an image unit
#[derive(Debug, Clone, Copy, Hash, PartialEq, Eq)]
pub struct ImageUnitBehavior {
    /// The mip level to bind
    pub level: u32,
    pub(crate) layer: Option<u32>,
    /// How the shader will access the image unit
    pub access: ImageUnitAccess,
    /// How the shader should interpret the image
    pub format: ImageUnitFormat,
}

impl Default for ImageUnitBehavior {
    #[inline]
    fn default() -> ImageUnitBehavior {
        ImageUnitBehavior {
            level: 0,
            layer: None,
            access: ImageUnitAccess::ReadWrite,
            format: ImageUnitFormat::R32I,
        }
    }
}

/// An image unit uniform marker
pub struct ImageUnit<'t, T: 't + core::ops::Deref<Target = crate::texture::TextureAny>>(pub &'t T, pub ImageUnitBehavior);

impl<'t, T: 't + core::ops::Deref<Target = crate::texture::TextureAny>> ImageUnit<'t, T> {
    /// Create a new marker
    pub fn new(texture: &'t T, format: ImageUnitFormat) -> Result<ImageUnit<'t, T>, ImageUnitError> {
        let tbits = texture.get_internal_format().unwrap().get_total_bits();
        if tbits != format.get_total_bits() {
            return Err(ImageUnitError::BadFormatClass(tbits, format.get_total_bits()))
        }

        Ok(ImageUnit(texture, ImageUnitBehavior {
	    format,
	    ..Default::default()
	}))
    }

    /// Set the mip level that will be bound
    pub fn set_level(mut self, level: u32) -> Result<Self, ImageUnitError> {
        self.0.mipmap(level).ok_or(ImageUnitError::NoMipmapAtLevel(level))?;
        self.1.level = level;
        Ok(self)
    }

    /// Sets the layer of the texture to bind, or None to disable layer binding
    // TODO: only implement this for texture types where layering makes sense
    pub fn set_layer(mut self, layer: Option<u32>) -> Result<Self, ImageUnitError> {
        if let Some(layer) = layer {
            match self.0.dimensions() {
                texture::Dimensions::Texture1d { width } =>
                    Err(ImageUnitError::LayeringNotSupported(self.0.dimensions())),
                texture::Dimensions::Texture2d { width, height } =>
                    Err(ImageUnitError::LayeringNotSupported(self.0.dimensions())),
                texture::Dimensions::Texture2dMultisample { width, height, samples } =>
                    Err(ImageUnitError::LayeringNotSupported(self.0.dimensions())),
                texture::Dimensions::Texture1dArray { width, array_size } =>
                    if layer >= array_size { Err(ImageUnitError::LayerOutOfBounds(layer))} else { Ok(()) },
                texture::Dimensions::Texture2dArray { width, height, array_size } =>
                    if layer >= array_size { Err(ImageUnitError::LayerOutOfBounds(layer))} else { Ok(()) },
                texture::Dimensions::Texture2dMultisampleArray { width, height, array_size, samples } =>
                    if layer >= array_size { Err(ImageUnitError::LayerOutOfBounds(layer))} else { Ok(()) },
                texture::Dimensions::Texture3d { width, height, depth } =>
                    if layer >= depth { Err(ImageUnitError::LayerOutOfBounds(layer))} else { Ok(()) },
                texture::Dimensions::Cubemap { dimension } =>
                    if layer >= 6 { Err(ImageUnitError::LayerOutOfBounds(layer))} else { Ok(()) },
                texture::Dimensions::CubemapArray { dimension, array_size } =>
                    if layer >= 6*array_size { Err(ImageUnitError::LayerOutOfBounds(layer))} else { Ok(()) },
            }?;
        }
        self.1.layer = layer;
        Ok(self)
    }

    /// State how the shader will access the image unit
    pub fn set_access(mut self, access: ImageUnitAccess) -> Self {
        self.1.access = access;
        self
    }

}

/// States how the shader will access the image unit
#[derive(Debug, Clone, Copy, Hash, PartialEq, Eq)]
pub enum ImageUnitAccess {
    /// The shader will only read from the image unit
    Read,
    /// The shader will only write to the image unit
    Write,
    /// The shader will perform both reads and writes to the image unit
    ReadWrite,
}

impl ToGlEnum for ImageUnitAccess {
    #[inline]
    fn to_glenum(&self) -> gl::types::GLenum {
        match *self {
            ImageUnitAccess::Read => gl::READ_ONLY,
            ImageUnitAccess::Write => gl::WRITE_ONLY,
            ImageUnitAccess::ReadWrite => gl::READ_WRITE,
        }
    }
}



/// How the shader should interpret the data in the image
#[derive(Debug, Clone, Copy, Hash, PartialEq, Eq)]
pub enum ImageUnitFormat {
    /// The image elements are 4-component 32 bit floating point
    RGBA32F,
    /// The image elements are 4-component 16 bit floating point
    RGBA16F,
    /// The image elements are 2-component 32 bit floating point
    RG32F,
    /// The image elements are 4-component 16 bit floating point
    RG16F,
    /// The image elements are 2 11-bit floats and 1 10-bit float
    R11FG11FB10F,
    /// The image elements are 1-component 32 bit floating point
    R32F,
    /// The image elements are 4-component 16 bit floating point
    R16F,

    /// The image elements are 4-component 32 bit unsigned integer
    RGBA32UI,
    /// The image elements are 4-component 16 bit unsigned integer
    RGBA16UI,
    /// The image elements have 3 10-bit unsigned integer components and 1 2-bit alpha component
    RGB10A2UI,
    /// The image elements are 4-component 8 bit unsigned integer
    RGBA8UI,
    /// The image elements are 2-component 32 bit unsigned integer
    RG32UI,
    /// The image elements are 2-component 16 bit unsigned integer
    RG16UI,
    /// The image elements are 2-component 8 bit unsigned integer
    RG8UI,
    /// The image elements are 1-component 32 bit unsigned integer
    R32UI,
    /// The image elements are 1-component 16 bit unsigned integer
    R16UI,
    /// The image elements are 1-component 8 bit unsigned integer
    R8UI,

    /// The image elements are 4-component 32 bit signed integer
    RGBA32I,
    /// The image elements are 4-component 16 bit signed integer
    RGBA16I,
    /// The image elements are 4-component 8 bit signed integer
    RGBA8I,
    /// The image elements are 2-component 32 bit signed integer
    RG32I,
    /// The image elements are 2-component 16 bit signed integer
    RG16I,
    /// The image elements are 2-component 8 bit signed integer
    RG8I,
    /// The image elements are 1-component 32 bit signed integer
    R32I,
    /// The image elements are 1-component 16 bit signed integer
    R16I,
    /// The image elements are 1-component 8 bit signed integer
    R8I,

    /// The image elements are 4-component 16 bit floating point
    RGBA16,
    /// The image elements are 3-component 10 bit floating point with 2 alpha bits
    RGB10A2,
    /// The image elements are 4-component 8 bit floating point
    RGBA8,
    /// The image elements are 2-component 16 bit floating point
    RG16,
    /// The image elements are 2-component 8 bit floating point
    RG8,
    /// The image elements are 1-component 16 bit floating point
    R16,
    /// The image elements are 1-component 8 bit floating point
    R8,

    /// The image elements are 4-component 16 bit floating point, normalized to the -1.0 to 1.0 range
    RGBA16snorm,
    /// The image elements are 4-component 8 bit floating point, normalized to the -1.0 to 1.0 range
    RGBA8snorm,
    /// The image elements are 2-component 16 bit floating point, normalized to the -1.0 to 1.0 range
    RG16snorm,
    /// The image elements are 2-component 8 bit floating point, normalized to the -1.0 to 1.0 range
    RG8snorm,
    /// The image elements are 1-component 16 bit floating point, normalized to the -1.0 to 1.0 range
    R16snorm,
    /// The image elements are 1-component 8 bit floating point, normalized to the -1.0 to 1.0 range
    R8snorm,
}

impl ImageUnitFormat {
    fn get_total_bits(&self) -> usize {
        match self {
            ImageUnitFormat::RGBA32F => 4*32,
            ImageUnitFormat::RGBA16F => 4*16,
            ImageUnitFormat::RG32F => 2*32,
            ImageUnitFormat::RG16F => 2*16,
            ImageUnitFormat::R11FG11FB10F => 11*2 + 10,
            ImageUnitFormat::R32F => 1*32,
            ImageUnitFormat::R16F => 1*16,

            ImageUnitFormat::RGBA32UI => 4*32,
            ImageUnitFormat::RGBA16UI => 4*16,
            ImageUnitFormat::RGB10A2UI => 3*10 + 2,
            ImageUnitFormat::RGBA8UI => 8*4,
            ImageUnitFormat::RG32UI => 2*32,
            ImageUnitFormat::RG16UI => 2*16,
            ImageUnitFormat::RG8UI => 2*8,
            ImageUnitFormat::R32UI => 1*32,
            ImageUnitFormat::R16UI => 1*16,
            ImageUnitFormat::R8UI => 1*8,

            ImageUnitFormat::RGBA32I => 4*32,
            ImageUnitFormat::RGBA16I => 2*32,
            ImageUnitFormat::RGBA8I => 4*8,
            ImageUnitFormat::RG32I => 2*32,
            ImageUnitFormat::RG16I => 2*16,
            ImageUnitFormat::RG8I => 2*8,
            ImageUnitFormat::R32I => 1*32,
            ImageUnitFormat::R16I => 1*16,
            ImageUnitFormat::R8I => 1*8,

            ImageUnitFormat::RGBA16 => 4*16,
            ImageUnitFormat::RGB10A2 => 3*10+2,
            ImageUnitFormat::RGBA8 => 4*8,
            ImageUnitFormat::RG16 => 2*16,
            ImageUnitFormat::RG8 => 2*8,
            ImageUnitFormat::R16 => 1*16,
            ImageUnitFormat::R8 => 1*8,

            ImageUnitFormat::RGBA16snorm => 4*16,
            ImageUnitFormat::RGBA8snorm => 4*8,
            ImageUnitFormat::RG16snorm => 2*16,
            ImageUnitFormat::RG8snorm => 2*8,
            ImageUnitFormat::R16snorm => 1*16,
            ImageUnitFormat::R8snorm => 1*8,
        }
    }
}

impl ToGlEnum for ImageUnitFormat {
    #[inline]
    fn to_glenum(&self) -> gl::types::GLenum {
        match *self {
            ImageUnitFormat::RGBA32F => gl::RGBA32F,
            ImageUnitFormat::RGBA16F => gl::RGBA16F,
            ImageUnitFormat::RG32F => gl::RG32F,
            ImageUnitFormat::RG16F => gl::RG16F,
            ImageUnitFormat::R11FG11FB10F => gl::R11F_G11F_B10F,
            ImageUnitFormat::R32F => gl::R32F,
            ImageUnitFormat::R16F => gl::R16F,

            ImageUnitFormat::RGBA32UI => gl::RGBA32UI,
            ImageUnitFormat::RGBA16UI => gl::RGBA16UI,
            ImageUnitFormat::RGB10A2UI => gl::RGB10_A2UI,
            ImageUnitFormat::RGBA8UI => gl::RGBA8UI,
            ImageUnitFormat::RG32UI => gl::RG32UI,
            ImageUnitFormat::RG16UI => gl::RG16UI,
            ImageUnitFormat::RG8UI => gl::RG8UI,
            ImageUnitFormat::R32UI => gl::R32UI,
            ImageUnitFormat::R16UI => gl::R16UI,
            ImageUnitFormat::R8UI => gl::R8UI,

            ImageUnitFormat::RGBA32I => gl::RGBA32I,
            ImageUnitFormat::RGBA16I => gl::RGBA16I,
            ImageUnitFormat::RGBA8I => gl::RGBA8I,
            ImageUnitFormat::RG32I => gl::RG32I,
            ImageUnitFormat::RG16I => gl::RG16I,
            ImageUnitFormat::RG8I => gl::RG8I,
            ImageUnitFormat::R32I => gl::R32I,
            ImageUnitFormat::R16I => gl::R16I,
            ImageUnitFormat::R8I => gl::R8I,

            ImageUnitFormat::RGBA16 => gl::RGBA16,
            ImageUnitFormat::RGB10A2 => gl::RGB10_A2,
            ImageUnitFormat::RGBA8 => gl::RGBA8,
            ImageUnitFormat::RG16 => gl::RG16,
            ImageUnitFormat::RG8 => gl::RG8,
            ImageUnitFormat::R16 => gl::R16,
            ImageUnitFormat::R8 => gl::R8,

            ImageUnitFormat::RGBA16snorm => gl::RGBA16_SNORM,
            ImageUnitFormat::RGBA8snorm => gl::RGBA8_SNORM,
            ImageUnitFormat::RG16snorm => gl::RG16_SNORM,
            ImageUnitFormat::RG8snorm => gl::RG8_SNORM,
            ImageUnitFormat::R16snorm => gl::R16_SNORM,
            ImageUnitFormat::R8snorm => gl::R8_SNORM,
        }
    }
}