glium 0.34.0

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.
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use crate::program::raw::RawProgram;


const MASK_HAS_TESS_EVAL: u8 = 0b00000001;
const MASK_HAS_TESS_CONTROL: u8 = 0b00000010;
const MASK_HAS_GEOMETRY: u8 = 0b00000100;

/// Glium attaches internal information to a binary to be able to fully restore the program.
pub fn attach_glium_header(raw: &RawProgram, data: &mut Vec<u8>) {
    let mut header_byte = 0u8;
    if raw.has_tessellation_evaluation_shader() {
        header_byte ^= MASK_HAS_TESS_EVAL;
    }
    if raw.has_tessellation_control_shader() {
        header_byte ^= MASK_HAS_TESS_CONTROL;
    }
    if raw.has_geometry_shader() {
        header_byte ^= MASK_HAS_GEOMETRY;
    }
    // TODO kind of inefficient.
    data.reserve(1);
    data.insert(0, header_byte);
}

/// Reads the first byte of the data (=glium header) and returns the corresponding shader flags.
/// If the header is not valid, returns None.
pub fn process_glium_header(data: &[u8]) -> Option<(bool, bool, bool)> {
    let header_byte = data[0];
    if header_byte >> 3 == 0 {
        let has_geometry_shader =                (header_byte & MASK_HAS_GEOMETRY) != 0;
        let has_tessellation_control_shader =    (header_byte & MASK_HAS_TESS_CONTROL) != 0;
        let has_tessellation_evaluation_shader = (header_byte & MASK_HAS_TESS_EVAL) != 0;
        Some((has_geometry_shader, has_tessellation_control_shader, has_tessellation_evaluation_shader))
    } else {
        None
    }
}