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use crate::{Pos2, Rect, Vec2};
/// Linearly transforms positions via a translation, then a scaling.
///
/// [`TSTransform`] first scales points with the scaling origin at `0, 0`
/// (the top left corner), then translates them.
#[repr(C)]
#[derive(Clone, Copy, Debug, PartialEq)]
#[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
#[cfg_attr(feature = "bytemuck", derive(bytemuck::Pod, bytemuck::Zeroable))]
pub struct TSTransform {
/// Scaling applied first, scaled around (0, 0).
pub scaling: f32,
/// Translation amount, applied after scaling.
pub translation: Vec2,
}
impl Eq for TSTransform {}
impl Default for TSTransform {
#[inline]
fn default() -> Self {
Self::IDENTITY
}
}
impl TSTransform {
pub const IDENTITY: Self = Self {
translation: Vec2::ZERO,
scaling: 1.0,
};
#[inline]
/// Creates a new translation that first scales points around
/// `(0, 0)`, then translates them.
pub fn new(translation: Vec2, scaling: f32) -> Self {
Self {
translation,
scaling,
}
}
#[inline]
pub fn from_translation(translation: Vec2) -> Self {
Self::new(translation, 1.0)
}
#[inline]
pub fn from_scaling(scaling: f32) -> Self {
Self::new(Vec2::ZERO, scaling)
}
/// Is this a valid, invertible transform?
pub fn is_valid(&self) -> bool {
self.scaling.is_finite() && self.translation.x.is_finite() && self.scaling != 0.0
}
/// Inverts the transform.
///
/// ```
/// # use emath::{pos2, vec2, TSTransform};
/// let p1 = pos2(2.0, 3.0);
/// let p2 = pos2(12.0, 5.0);
/// let ts = TSTransform::new(vec2(2.0, 3.0), 2.0);
/// let inv = ts.inverse();
/// assert_eq!(inv.mul_pos(p1), pos2(0.0, 0.0));
/// assert_eq!(inv.mul_pos(p2), pos2(5.0, 1.0));
///
/// assert_eq!(ts.inverse().inverse(), ts);
/// ```
#[inline]
pub fn inverse(&self) -> Self {
Self::new(-self.translation / self.scaling, 1.0 / self.scaling)
}
/// Transforms the given coordinate.
///
/// ```
/// # use emath::{pos2, vec2, TSTransform};
/// let p1 = pos2(0.0, 0.0);
/// let p2 = pos2(5.0, 1.0);
/// let ts = TSTransform::new(vec2(2.0, 3.0), 2.0);
/// assert_eq!(ts.mul_pos(p1), pos2(2.0, 3.0));
/// assert_eq!(ts.mul_pos(p2), pos2(12.0, 5.0));
/// ```
#[inline]
pub fn mul_pos(&self, pos: Pos2) -> Pos2 {
self.scaling * pos + self.translation
}
/// Transforms the given rectangle.
///
/// ```
/// # use emath::{pos2, vec2, Rect, TSTransform};
/// let rect = Rect::from_min_max(pos2(5.0, 5.0), pos2(15.0, 10.0));
/// let ts = TSTransform::new(vec2(1.0, 0.0), 3.0);
/// let transformed = ts.mul_rect(rect);
/// assert_eq!(transformed.min, pos2(16.0, 15.0));
/// assert_eq!(transformed.max, pos2(46.0, 30.0));
/// ```
#[inline]
pub fn mul_rect(&self, rect: Rect) -> Rect {
Rect {
min: self.mul_pos(rect.min),
max: self.mul_pos(rect.max),
}
}
}
/// Transforms the position.
impl std::ops::Mul<Pos2> for TSTransform {
type Output = Pos2;
#[inline]
fn mul(self, pos: Pos2) -> Pos2 {
self.mul_pos(pos)
}
}
/// Transforms the rectangle.
impl std::ops::Mul<Rect> for TSTransform {
type Output = Rect;
#[inline]
fn mul(self, rect: Rect) -> Rect {
self.mul_rect(rect)
}
}
impl std::ops::Mul<Self> for TSTransform {
type Output = Self;
#[inline]
/// Applies the right hand side transform, then the left hand side.
///
/// ```
/// # use emath::{TSTransform, vec2};
/// let ts1 = TSTransform::new(vec2(1.0, 0.0), 2.0);
/// let ts2 = TSTransform::new(vec2(-1.0, -1.0), 3.0);
/// let ts_combined = TSTransform::new(vec2(2.0, -1.0), 6.0);
/// assert_eq!(ts_combined, ts2 * ts1);
/// ```
fn mul(self, rhs: Self) -> Self::Output {
// Apply rhs first.
Self {
scaling: self.scaling * rhs.scaling,
translation: self.translation + self.scaling * rhs.translation,
}
}
}