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use core::{
marker::PhantomData,
ops::{Deref, DerefMut},
};
use crate::cast::{self, ArrayCast};
use super::{FromColor, FromColorUnclampedMut, FromColorUnclampedMutGuard, IntoColor};
/// Temporarily convert colors in place.
///
/// It allows colors to be converted without using more additional memory than
/// what is necessary for the conversion, itself. The conversion will however
/// have to be reverted at some point, since the memory space is borrowed and
/// has to be restored to its original format. This is enforced by a scope guard
/// that does the opposite conversion when it's dropped.
///
/// See also [`IntoColorMut`] and [`FromColorUnclampedMut`].
///
/// ```
/// use palette::{FromColorMut, ShiftHueAssign, Srgb, Hsv};
///
/// let mut rgb = [
/// Srgb::new(1.0, 0.0, 0.0),
/// Srgb::new(0.0, 1.0, 0.0),
/// Srgb::new(0.0, 0.0, 1.0),
/// ];
///
/// {
/// let mut hsv = <[Hsv]>::from_color_mut(&mut rgb);
///
/// // All of the colors in `rgb` have been converted to `Hsv`:
/// assert_eq!(
/// *hsv,
/// [
/// Hsv::new(0.0, 1.0, 1.0),
/// Hsv::new(120.0, 1.0, 1.0),
/// Hsv::new(240.0, 1.0, 1.0),
/// ]
/// );
///
/// hsv.shift_hue_assign(60.0);
///
/// } // The guard is dropped here and the colors are restored to `Srgb`.
///
/// // Notice how the colors in `rgb` have changed:
/// assert_eq!(
/// rgb,
/// [
/// Srgb::new(1.0, 1.0, 0.0),
/// Srgb::new(0.0, 1.0, 1.0),
/// Srgb::new(1.0, 0.0, 1.0),
/// ]
/// );
/// ```
///
/// The scope guard, [`FromColorMutGuard`], has a few extra methods that can
/// make multiple conversion steps more efficient. One of those is
/// [`FromColorMutGuard::then_into_color_mut`], which works like
/// [`IntoColorMut::into_color_mut`], but does not add an extra step when
/// restoring to the original color type. This example will convert `Srgb → Hsv
/// → Hsl → Srgb` instead of `Srgb → Hsv → Hsl → Hsv → Srgb`:
///
/// ```
/// use palette::{FromColorMut, ShiftHueAssign, LightenAssign, Srgb, Hsv, Hsl};
///
/// let mut rgb = [
/// Srgb::new(1.0, 0.0, 0.0),
/// Srgb::new(0.0, 1.0, 0.0),
/// Srgb::new(0.0, 0.0, 1.0),
/// ];
///
/// {
/// let mut hsv = <[Hsv]>::from_color_mut(&mut rgb);
/// hsv.shift_hue_assign(60.0);
///
/// let mut hsl = hsv.then_into_color_mut::<[Hsl]>();
/// hsl.lighten_assign(0.5);
///
/// } // `then_into_color_mut` makes the guard restore directly to `Srgb` here.
///
/// // Notice how the colors in `rgb` have changed:
/// assert_eq!(
/// rgb,
/// [
/// Srgb::new(1.0, 1.0, 0.5),
/// Srgb::new(0.5, 1.0, 1.0),
/// Srgb::new(1.0, 0.5, 1.0),
/// ]
/// );
/// ```
///
/// # Note
///
/// The reused memory space could end up with unexpected values if the
/// conversion panics or if the scope guard's `drop` function doesn't run. The
/// default implementations of `FromColorMut` uses [`ArrayCast`], which is only
/// implemented for color types that can safely accept and recover from any
/// value. Other color types will have to provide their own implementations that
/// can handle this case.
pub trait FromColorMut<T>
where
T: ?Sized + FromColorMut<Self>,
{
/// Temporarily convert from another color type in place.
///
/// This reuses the memory space, and the returned scope guard will restore
/// the converted colors to their original type when it's dropped.
#[must_use]
fn from_color_mut(color: &mut T) -> FromColorMutGuard<Self, T>;
}
impl<T, U> FromColorMut<U> for T
where
T: FromColor<U> + ArrayCast + Clone,
U: FromColor<T> + ArrayCast<Array = T::Array> + Clone,
{
#[inline]
fn from_color_mut(color: &mut U) -> FromColorMutGuard<Self, U> {
let color_clone = color.clone();
let result: &mut T = cast::from_array_mut(cast::into_array_mut(color));
*result = color_clone.into_color();
FromColorMutGuard {
current: Some(result),
original: PhantomData,
}
}
}
impl<T, U> FromColorMut<[U]> for [T]
where
T: FromColorMut<U> + ArrayCast + ?Sized,
U: FromColorMut<T> + ArrayCast<Array = T::Array> + ?Sized,
{
#[inline]
fn from_color_mut(colors: &mut [U]) -> FromColorMutGuard<Self, [U]> {
for color in &mut *colors {
// Forgetting the guard leaves the colors in the converted state.
core::mem::forget(T::from_color_mut(color));
}
FromColorMutGuard {
current: Some(cast::from_array_slice_mut(cast::into_array_slice_mut(
colors,
))),
original: PhantomData,
}
}
}
/// Temporarily convert colors in place. The `Into` counterpart to
/// [`FromColorMut`].
///
/// See [`FromColorMut`] for more details and examples.
///
/// ```
/// use palette::{IntoColorMut, ShiftHueAssign, Srgb, Hsv};
///
/// let mut rgb = [
/// Srgb::new(1.0, 0.0, 0.0),
/// Srgb::new(0.0, 1.0, 0.0),
/// Srgb::new(0.0, 0.0, 1.0),
/// ];
///
/// {
/// let hsv: &mut [Hsv] = &mut rgb.into_color_mut(); // The guard is coerced into a slice.
///
/// // All of the colors in `rgb` have been converted to `Hsv`:
/// assert_eq!(
/// hsv,
/// [
/// Hsv::new(0.0, 1.0, 1.0),
/// Hsv::new(120.0, 1.0, 1.0),
/// Hsv::new(240.0, 1.0, 1.0),
/// ]
/// );
///
/// hsv.shift_hue_assign(60.0);
///
/// } // The guard is dropped here and the colors are restored to `Srgb`.
///
/// // Notice how the colors in `rgb` have changed:
/// assert_eq!(
/// rgb,
/// [
/// Srgb::new(1.0, 1.0, 0.0),
/// Srgb::new(0.0, 1.0, 1.0),
/// Srgb::new(1.0, 0.0, 1.0),
/// ]
/// );
/// ```
pub trait IntoColorMut<T>: FromColorMut<T>
where
T: ?Sized + FromColorMut<Self>,
{
/// Temporarily convert to another color type in place.
///
/// This reuses the memory space, and the returned scope guard will restore
/// the converted colors to their original type when it's dropped.
#[allow(clippy::wrong_self_convention)]
#[must_use]
fn into_color_mut(&mut self) -> FromColorMutGuard<T, Self>;
}
impl<T, U> IntoColorMut<T> for U
where
T: FromColorMut<U> + ?Sized,
U: FromColorMut<T> + ?Sized,
{
#[inline]
fn into_color_mut(&mut self) -> FromColorMutGuard<T, Self> {
T::from_color_mut(self)
}
}
/// A scope guard that restores the guarded colors to their original type when
/// dropped.
#[repr(transparent)]
pub struct FromColorMutGuard<'a, T, U>
where
T: FromColorMut<U> + ?Sized,
U: FromColorMut<T> + ?Sized,
{
// `Option` lets us move out without triggering `Drop`.
pub(super) current: Option<&'a mut T>,
pub(super) original: PhantomData<&'a mut U>,
}
impl<'a, T, U> FromColorMutGuard<'a, T, U>
where
T: FromColorMut<U> + ?Sized,
U: FromColorMut<T> + ?Sized,
{
/// Convert the colors to another type and replace this guard.
///
/// The colors will not be converted back to the current color type before
/// being restored, as opposed to when `into_color_mut` is called. Instead,
/// they are restored directly to their original type.
#[must_use]
#[inline]
pub fn then_into_color_mut<C>(mut self) -> FromColorMutGuard<'a, C, U>
where
T: FromColorMut<C>,
C: FromColorMut<U> + FromColorMut<T> + ?Sized,
U: FromColorMut<C>,
{
FromColorMutGuard {
current: self
.current
.take()
.map(C::from_color_mut)
.and_then(|mut guard| guard.current.take()),
original: PhantomData,
}
}
/// Convert the colors to another type, without clamping, and replace this
/// guard.
///
/// The colors will not be converted back to the current color type before
/// being restored, as opposed to when `into_color_unclamped_mut` is called.
/// Instead, they are restored directly to their original type.
#[must_use]
#[inline]
pub fn then_into_color_unclamped_mut<C>(mut self) -> FromColorUnclampedMutGuard<'a, C, U>
where
T: FromColorUnclampedMut<C>,
C: FromColorUnclampedMut<U> + FromColorUnclampedMut<T> + ?Sized,
U: FromColorUnclampedMut<C>,
{
FromColorUnclampedMutGuard {
current: self
.current
.take()
.map(C::from_color_unclamped_mut)
.and_then(|mut guard| guard.current.take()),
original: PhantomData,
}
}
/// Replace this guard with a guard that does not clamp the colors after restoring.
#[must_use]
#[inline]
pub fn into_unclamped_guard(mut self) -> FromColorUnclampedMutGuard<'a, T, U>
where
T: FromColorUnclampedMut<U>,
U: FromColorUnclampedMut<T>,
{
FromColorUnclampedMutGuard {
current: self.current.take(),
original: PhantomData,
}
}
/// Immediately restore the colors to their original type.
///
/// This happens automatically when the guard is dropped, but there may be
/// situations where it's better or more convenient to call `restore`
/// directly.
#[inline]
pub fn restore(mut self) -> &'a mut U {
let restored = self
.current
.take()
.map(U::from_color_mut)
.and_then(|mut guard| guard.current.take());
if let Some(restored) = restored {
restored
} else {
unreachable!()
}
}
}
impl<'a, T, U> Deref for FromColorMutGuard<'a, T, U>
where
T: FromColorMut<U> + ?Sized,
U: FromColorMut<T> + ?Sized,
{
type Target = T;
#[inline]
fn deref(&self) -> &Self::Target {
if let Some(current) = self.current.as_ref() {
current
} else {
unreachable!()
}
}
}
impl<'a, T, U> DerefMut for FromColorMutGuard<'a, T, U>
where
T: FromColorMut<U> + ?Sized,
U: FromColorMut<T> + ?Sized,
{
#[inline]
fn deref_mut(&mut self) -> &mut Self::Target {
if let Some(current) = self.current.as_mut() {
current
} else {
unreachable!()
}
}
}
impl<'a, T, U> Drop for FromColorMutGuard<'a, T, U>
where
T: FromColorMut<U> + ?Sized,
U: FromColorMut<T> + ?Sized,
{
#[inline]
fn drop(&mut self) {
// Forgetting the guard leaves the colors in the converted state.
core::mem::forget(self.current.take().map(U::from_color_mut));
}
}