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// Copyright 2014 The Servo Project Developers. See the COPYRIGHT // file at the top-level directory of this distribution. // // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your // option. This file may not be copied, modified, or distributed // except according to those terms. //! A type-checked scaling factor between units. use num::One; use num_traits::NumCast; #[cfg(feature = "serde")] use serde; use core::fmt; use core::ops::{Add, Div, Mul, Neg, Sub}; use core::hash::{Hash, Hasher}; use core::marker::PhantomData; use core::cmp::Ordering; use {Point2D, Rect, Size2D, Vector2D}; /// A scaling factor between two different units of measurement. /// /// This is effectively a type-safe float, intended to be used in combination with other types like /// `length::Length` to enforce conversion between systems of measurement at compile time. /// /// `Src` and `Dst` represent the units before and after multiplying a value by a `Scale`. They /// may be types without values, such as empty enums. For example: /// /// ```rust /// use euclid::Scale; /// use euclid::Length; /// enum Mm {}; /// enum Inch {}; /// /// let mm_per_inch: Scale<f32, Inch, Mm> = Scale::new(25.4); /// /// let one_foot: Length<f32, Inch> = Length::new(12.0); /// let one_foot_in_mm: Length<f32, Mm> = one_foot * mm_per_inch; /// ``` #[repr(C)] #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))] #[cfg_attr(feature = "serde", serde(bound(serialize = "T: serde::Serialize", deserialize = "T: serde::Deserialize<'de>")))] pub struct Scale<T, Src, Dst>(pub T, #[doc(hidden)] pub PhantomData<(Src, Dst)>); impl<T, Src, Dst> Scale<T, Src, Dst> { #[inline] pub const fn new(x: T) -> Self { Scale(x, PhantomData) } /// Returns the given point transformed by this scale. /// /// # Example /// /// ```rust /// use euclid::{Scale, point2}; /// enum Mm {}; /// enum Cm {}; /// /// let to_mm: Scale<i32, Cm, Mm> = Scale::new(10); /// /// assert_eq!(to_mm.transform_point(point2(42, -42)), point2(420, -420)); /// ``` #[inline] pub fn transform_point(&self, point: Point2D<T, Src>) -> Point2D<T::Output, Dst> where T: Clone + Mul { Point2D::new(point.x * self.get(), point.y * self.get()) } /// Returns the given vector transformed by this scale. /// /// # Example /// /// ```rust /// use euclid::{Scale, vec2}; /// enum Mm {}; /// enum Cm {}; /// /// let to_mm: Scale<i32, Cm, Mm> = Scale::new(10); /// /// assert_eq!(to_mm.transform_vector(vec2(42, -42)), vec2(420, -420)); /// ``` #[inline] pub fn transform_vector(&self, vec: Vector2D<T, Src>) -> Vector2D<T::Output, Dst> where T: Clone + Mul { Vector2D::new(vec.x * self.get(), vec.y * self.get()) } /// Returns the given vector transformed by this scale. /// /// # Example /// /// ```rust /// use euclid::{Scale, size2}; /// enum Mm {}; /// enum Cm {}; /// /// let to_mm: Scale<i32, Cm, Mm> = Scale::new(10); /// /// assert_eq!(to_mm.transform_size(size2(42, -42)), size2(420, -420)); /// ``` #[inline] pub fn transform_size(&self, size: Size2D<T, Src>) -> Size2D<T::Output, Dst> where T: Clone + Mul { Size2D::new(size.width * self.get(), size.height * self.get()) } /// Returns the given rect transformed by this scale. /// /// # Example /// /// ```rust /// use euclid::{Scale, rect}; /// enum Mm {}; /// enum Cm {}; /// /// let to_mm: Scale<i32, Cm, Mm> = Scale::new(10); /// /// assert_eq!(to_mm.transform_rect(&rect(1, 2, 42, -42)), rect(10, 20, 420, -420)); /// ``` #[inline] pub fn transform_rect(&self, rect: &Rect<T, Src>) -> Rect<T::Output, Dst> where T: Copy + Mul { Rect::new( self.transform_point(rect.origin), self.transform_size(rect.size), ) } /// Returns the inverse of this scale. #[inline] pub fn inverse(&self) -> Scale<T::Output, Dst, Src> where T: Clone + Neg { Scale::new(-self.get()) } /// Returns `true` if this scale has no effect. /// /// # Example /// /// ```rust /// use euclid::Scale; /// use euclid::num::One; /// enum Mm {}; /// enum Cm {}; /// /// let cm_per_mm: Scale<f32, Mm, Cm> = Scale::new(0.1); /// let mm_per_mm: Scale<f32, Mm, Mm> = Scale::new(1.0); /// /// assert_eq!(cm_per_mm.is_identity(), false); /// assert_eq!(mm_per_mm.is_identity(), true); /// assert_eq!(mm_per_mm, Scale::one()); /// ``` #[inline] pub fn is_identity(&self) -> bool where T: PartialEq + One { self.0 == T::one() } } impl<T: Clone, Src, Dst> Scale<T, Src, Dst> { #[inline] pub fn get(&self) -> T { self.0.clone() } /// The inverse Scale (1.0 / self). /// /// # Example /// /// ```rust /// use euclid::Scale; /// enum Mm {}; /// enum Cm {}; /// /// let cm_per_mm: Scale<f32, Cm, Mm> = Scale::new(0.1); /// /// assert_eq!(cm_per_mm.inv(), Scale::new(10.0)); /// ``` pub fn inv(&self) -> Scale<T::Output, Dst, Src> where T: One + Div { let one: T = One::one(); Scale::new(one / self.0.clone()) } } impl<T: NumCast + Clone, Src, Dst> Scale<T, Src, Dst> { /// Cast from one numeric representation to another, preserving the units. /// /// # Panics /// /// If the source value cannot be represented by the target type `NewT`, then /// method panics. Use `try_cast` if that must be case. /// /// # Example /// /// ```rust /// use euclid::Scale; /// enum Mm {}; /// enum Cm {}; /// /// let to_mm: Scale<i32, Cm, Mm> = Scale::new(10); /// /// assert_eq!(to_mm.cast::<f32>(), Scale::new(10.0)); /// ``` /// That conversion will panic, because `i32` not enough to store such big numbers: /// ```rust,should_panic /// use euclid::Scale; /// enum Mm {};// millimeter = 10^-2 meters /// enum Em {};// exameter = 10^18 meters /// /// // Panics /// let to_em: Scale<i32, Mm, Em> = Scale::new(10e20).cast(); /// ``` #[inline] pub fn cast<NewT: NumCast>(&self) -> Scale<NewT, Src, Dst> { self.try_cast().unwrap() } /// Fallible cast from one numeric representation to another, preserving the units. /// If the source value cannot be represented by the target type `NewT`, then `None` /// is returned. /// /// # Example /// /// ```rust /// use euclid::Scale; /// enum Mm {}; /// enum Cm {}; /// enum Em {};// Exameter = 10^18 meters /// /// let to_mm: Scale<i32, Cm, Mm> = Scale::new(10); /// let to_em: Scale<f32, Mm, Em> = Scale::new(10e20); /// /// assert_eq!(to_mm.try_cast::<f32>(), Some(Scale::new(10.0))); /// // Integer to small to store that number /// assert_eq!(to_em.try_cast::<i32>(), None); /// ``` pub fn try_cast<NewT: NumCast>(&self) -> Option<Scale<NewT, Src, Dst>> { NumCast::from(self.get()).map(Scale::new) } } impl<Src, Dst> Scale<f32, Src, Dst> { /// Identity scaling, could be used to safely transit from one space to another. pub const ONE: Self = Scale(1.0, PhantomData); } // scale0 * scale1 // (A,B) * (B,C) = (A,C) impl<T: Mul, A, B, C> Mul<Scale<T, B, C>> for Scale<T, A, B> { type Output = Scale<T::Output, A, C>; #[inline] fn mul(self, other: Scale<T, B, C>) -> Self::Output { Scale::new(self.0 * other.0) } } // scale0 + scale1 impl<T: Add, Src, Dst> Add for Scale<T, Src, Dst> { type Output = Scale<T::Output, Src, Dst>; #[inline] fn add(self, other: Scale<T, Src, Dst>) -> Self::Output { Scale::new(self.0 + other.0) } } // scale0 - scale1 impl<T: Sub, Src, Dst> Sub for Scale<T, Src, Dst> { type Output = Scale<T::Output, Src, Dst>; #[inline] fn sub(self, other: Scale<T, Src, Dst>) -> Self::Output { Scale::new(self.0 - other.0) } } // FIXME: Switch to `derive(PartialEq, Clone)` after this Rust issue is fixed: // https://github.com/rust-lang/rust/issues/26925 impl<T: PartialEq, Src, Dst> PartialEq for Scale<T, Src, Dst> { fn eq(&self, other: &Scale<T, Src, Dst>) -> bool { self.0 == other.0 } } impl<T: Eq, Src, Dst> Eq for Scale<T, Src, Dst> {} impl<T: PartialOrd, Src, Dst> PartialOrd for Scale<T, Src, Dst> { fn partial_cmp(&self, other: &Self) -> Option<Ordering> { self.0.partial_cmp(&other.0) } } impl<T: Ord, Src, Dst> Ord for Scale<T, Src, Dst> { fn cmp(&self, other: &Self) -> Ordering { self.0.cmp(&other.0) } } impl<T: Clone, Src, Dst> Clone for Scale<T, Src, Dst> { fn clone(&self) -> Scale<T, Src, Dst> { Scale::new(self.get()) } } impl<T: Copy, Src, Dst> Copy for Scale<T, Src, Dst> {} impl<T: fmt::Debug, Src, Dst> fmt::Debug for Scale<T, Src, Dst> { fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { self.0.fmt(f) } } impl<T: fmt::Display, Src, Dst> fmt::Display for Scale<T, Src, Dst> { fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { self.0.fmt(f) } } impl<T: Default, Src, Dst> Default for Scale<T, Src, Dst> { fn default() -> Self { Self::new(T::default()) } } impl<T: Hash, Src, Dst> Hash for Scale<T, Src, Dst> { fn hash<H: Hasher>(&self, state: &mut H) { self.0.hash(state) } } impl<T: One, Src, Dst> One for Scale<T, Src, Dst> { #[inline] fn one() -> Self { Scale::new(T::one()) } } #[cfg(test)] mod tests { use super::Scale; enum Inch {} enum Cm {} enum Mm {} #[test] fn test_scale() { let mm_per_inch: Scale<f32, Inch, Mm> = Scale::new(25.4); let cm_per_mm: Scale<f32, Mm, Cm> = Scale::new(0.1); let mm_per_cm: Scale<f32, Cm, Mm> = cm_per_mm.inv(); assert_eq!(mm_per_cm.get(), 10.0); let one: Scale<f32, Mm, Mm> = cm_per_mm * mm_per_cm; assert_eq!(one.get(), 1.0); let one: Scale<f32, Cm, Cm> = mm_per_cm * cm_per_mm; assert_eq!(one.get(), 1.0); let cm_per_inch: Scale<f32, Inch, Cm> = mm_per_inch * cm_per_mm; // mm cm cm // ---- x ---- = ---- // inch mm inch assert_eq!(cm_per_inch, Scale::new(2.54)); let a: Scale<isize, Inch, Inch> = Scale::new(2); let b: Scale<isize, Inch, Inch> = Scale::new(3); assert_ne!(a, b); assert_eq!(a, a.clone()); assert_eq!(a.clone() + b.clone(), Scale::new(5)); assert_eq!(a - b, Scale::new(-1)); } }