web-glitz 0.2.1

Rusty low-level web-graphics library on top of WebGL 2.0.
Documentation 
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use std::marker::PhantomData;
use std::mem;

use super::{GpuTask, Progress};

pub(crate) enum MaybeDone<T, O, Ec> {
    NotYet(T, PhantomData<Ec>),
    Done(O),
    Gone,
}

impl<T, O, Ec> MaybeDone<T, O, Ec>
where
    T: GpuTask<Ec, Output = O>,
{
    pub fn progress(&mut self, execution_context: &mut Ec) -> bool {
        let res = match self {
            MaybeDone::Done(_) => return true,
            MaybeDone::NotYet(ref mut task, _) => task.progress(execution_context),
            MaybeDone::Gone => panic!("Cannot progress a Join twice."),
        };

        match res {
            Progress::Finished(output) => {
                *self = MaybeDone::Done(output);

                true
            }
            Progress::ContinueFenced => false,
        }
    }

    pub fn take(&mut self) -> O {
        match mem::replace(self, MaybeDone::Gone) {
            MaybeDone::Done(a) => a,
            _ => panic!(),
        }
    }
}

impl<T, O, Ec> Clone for MaybeDone<T, O, Ec>
where
    T: Clone,
    O: Clone,
{
    fn clone(&self) -> Self {
        match self {
            MaybeDone::NotYet(task, _) => MaybeDone::NotYet(task.clone(), PhantomData),
            MaybeDone::Done(output) => MaybeDone::Done(output.clone()),
            MaybeDone::Gone => MaybeDone::Gone,
        }
    }
}

pub(crate) fn maybe_done<T, O, Ec>(task: T) -> MaybeDone<T, O, Ec>
where
    T: GpuTask<Ec, Output = O>,
{
    MaybeDone::NotYet(task, PhantomData)
}