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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/*!

This module handles the fences of a buffer.

*/
use smallvec::SmallVec;
use std::cell::RefCell;
use std::ops::Range;

use crate::context::CommandContext;
use crate::sync::{self, LinearSyncFence};

/// Contains a list of fences.
pub struct Fences {
    fences: RefCell<SmallVec<[(Range<usize>, LinearSyncFence); 16]>>,
}

impl Fences {
    /// Initialization.
    pub fn new() -> Fences {
        Fences {
            fences: RefCell::new(SmallVec::new()),
        }
    }

    /// Creates an `Inserter` that allows inserting a fence in the list for the given range.
    #[inline]
    pub fn inserter(&self, range: Range<usize>) -> Inserter<'_> {
        Inserter {
            fences: self,
            range,
        }
    }

    /// Waits until the given range is accessible.
    pub fn wait(&self, ctxt: &mut CommandContext<'_>, range: Range<usize>) {
        let mut existing_fences = self.fences.borrow_mut();
        let mut new_fences = SmallVec::new();

        for existing in existing_fences.drain(..) {
            if (existing.0.start >= range.start && existing.0.start < range.end) ||
               (existing.0.end > range.start && existing.0.end < range.end)
            {
                unsafe { sync::wait_linear_sync_fence_and_drop(existing.1, ctxt) };
            } else {
                new_fences.push(existing);
            }
        }

        *existing_fences = new_fences;
    }

    /// Cleans up all fences in the container. Must be called or you'll get a panic.
    pub fn clean(&mut self, ctxt: &mut CommandContext<'_>) {
        let mut fences = self.fences.borrow_mut();
        for (_, sync) in fences.drain(..) {
            unsafe { sync::destroy_linear_sync_fence(ctxt, sync) };
        }
    }
}

/// Allows inserting a fence in the list.
pub struct Inserter<'a> {
    fences: &'a Fences,
    range: Range<usize>,
}

impl<'a> Inserter<'a> {
    /// Inserts a new fence.
    pub fn insert(self, ctxt: &mut CommandContext<'_>) {
        let mut new_fences = SmallVec::new();

        let mut written = false;

        let mut existing_fences = self.fences.fences.borrow_mut();
        for existing in existing_fences.drain(..) {
            if existing.0.start < self.range.start && existing.0.end <= self.range.start {
                new_fences.push(existing);

            } else if existing.0.start < self.range.start && existing.0.end >= self.range.end {
                // we are stuck here, because we can't duplicate a fence
                // so instead we just extend the new fence to the existing one
                let new_fence = unsafe { sync::new_linear_sync_fence(ctxt).unwrap() };
                new_fences.push((existing.0.start .. self.range.start, existing.1));
                new_fences.push((self.range.start .. existing.0.end, new_fence));
                written = true;

            } else if existing.0.start < self.range.start && existing.0.end >= self.range.start {
                new_fences.push((existing.0.start .. self.range.start, existing.1));
                if !written {
                    let new_fence = unsafe { sync::new_linear_sync_fence(ctxt).unwrap() };
                    new_fences.push((self.range.clone(), new_fence));
                    written = true;
                }

            } else if existing.0.start >= self.range.start && existing.0.end <= self.range.end {
                unsafe { sync::destroy_linear_sync_fence(ctxt, existing.1) };
                if !written {
                    let new_fence = unsafe { sync::new_linear_sync_fence(ctxt).unwrap() };
                    new_fences.push((self.range.clone(), new_fence));
                    written = true;
                }

            } else if existing.0.start >= self.range.end {
                if !written {
                    let new_fence = unsafe { sync::new_linear_sync_fence(ctxt).unwrap() };
                    new_fences.push((self.range.clone(), new_fence));
                    written = true;
                }

                new_fences.push(existing);

            } else {
                if !written {
                    let new_fence = unsafe { sync::new_linear_sync_fence(ctxt).unwrap() };
                    new_fences.push((self.range.clone(), new_fence));
                    written = true;
                }

                new_fences.push((self.range.end .. existing.0.end, existing.1));
            }
        }

        if !written {
            let new_fence = unsafe { sync::new_linear_sync_fence(ctxt).unwrap() };
            new_fences.push((self.range, new_fence));
        }

        *existing_fences = new_fences;
    }
}