blob: 9a9dd9b6338d88fa9b204ea97dea1020db2448b7 [file] [log] [blame]
// Copyright 2022 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
use std::{convert::TryFrom, error::Error, fmt};
use crate::{path::MAX_ERROR, AffineTransform, Point, MAX_HEIGHT, MAX_WIDTH};
const MAX_SCALING_FACTOR_X: f32 = 1.0 + MAX_ERROR as f32 / MAX_WIDTH as f32;
const MAX_SCALING_FACTOR_Y: f32 = 1.0 + MAX_ERROR as f32 / MAX_HEIGHT as f32;
#[derive(Debug, Eq, PartialEq)]
pub enum GeomPresTransformError {
ExceededScalingFactor { x: bool, y: bool },
}
impl fmt::Display for GeomPresTransformError {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
match self {
GeomPresTransformError::ExceededScalingFactor { x: true, y: false } => {
write!(f, "exceeded scaling factor on the X axis (-1.0 to 1.0)")
}
GeomPresTransformError::ExceededScalingFactor { x: false, y: true } => {
write!(f, "exceeded scaling factor on the Y axis (-1.0 to 1.0)")
}
GeomPresTransformError::ExceededScalingFactor { x: true, y: true } => {
write!(f, "exceeded scaling factor on both axis (-1.0 to 1.0)")
}
_ => panic!("cannot display invalid GeomPresTransformError"),
}
}
}
impl Error for GeomPresTransformError {}
#[derive(Default, Clone, Copy, Debug, Eq, PartialEq)]
pub struct GeomPresTransform(pub(crate) AffineTransform);
impl GeomPresTransform {
/// ```text
/// [ x' ] [ t.0 t.1 t.4 ] [ x ]
/// [ y' ] = [ t.2 t.3 t.5 ] [ y ]
/// [ 1 ] [ 0 0 1 ] [ 1 ]
/// ```
#[inline]
pub fn new(mut transform: [f32; 9]) -> Option<Self> {
(transform[6].abs() <= f32::EPSILON && transform[7].abs() <= f32::EPSILON)
.then(|| {
if (transform[8] - 1.0).abs() > f32::EPSILON {
let recip = transform[8].recip();
for val in &mut transform[..6] {
*val *= recip;
}
}
Self::try_from(AffineTransform {
ux: transform[0],
vx: transform[1],
uy: transform[3],
vy: transform[4],
tx: transform[2],
ty: transform[5],
})
.ok()
})
.flatten()
}
pub fn is_identity(&self) -> bool {
self.0.is_identity()
}
pub(crate) fn transform(&self, point: Point) -> Point {
self.0.transform(point)
}
#[inline]
pub fn as_slice(&self) -> [f32; 6] {
[self.0.ux, self.0.vx, self.0.uy, self.0.vy, self.0.tx, self.0.ty]
}
}
impl TryFrom<[f32; 6]> for GeomPresTransform {
type Error = GeomPresTransformError;
fn try_from(transform: [f32; 6]) -> Result<Self, Self::Error> {
GeomPresTransform::try_from(AffineTransform::from(transform))
}
}
impl TryFrom<AffineTransform> for GeomPresTransform {
type Error = GeomPresTransformError;
fn try_from(t: AffineTransform) -> Result<Self, Self::Error> {
let scales_up_x = t.ux * t.ux + t.uy * t.uy > MAX_SCALING_FACTOR_X;
let scales_up_y = t.vx * t.vx + t.vy * t.vy > MAX_SCALING_FACTOR_Y;
(!scales_up_x && !scales_up_y)
.then(|| Self(t))
.ok_or(GeomPresTransformError::ExceededScalingFactor { x: scales_up_x, y: scales_up_y })
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn default_identity() {
let transform = GeomPresTransform::default();
assert_eq!(transform.transform(Point::new(2.0, 3.0)), Point::new(2.0, 3.0));
}
#[test]
fn as_slice() {
let slice = [0.1, 0.5, 0.4, 0.3, 0.7, 0.9];
assert_eq!(slice, GeomPresTransform::try_from(slice).unwrap().as_slice());
}
#[test]
fn scale_translate() {
let transform = GeomPresTransform::try_from([0.1, 0.5, 0.4, 0.3, 0.5, 0.6]).unwrap();
assert_eq!(transform.transform(Point::new(2.0, 3.0)), Point::new(2.2, 2.3));
}
#[test]
fn wrong_scaling_factor() {
let transform =
[0.1, MAX_SCALING_FACTOR_Y.sqrt(), MAX_SCALING_FACTOR_X.sqrt(), 0.1, 0.5, 0.0];
assert_eq!(
GeomPresTransform::try_from(transform),
Err(GeomPresTransformError::ExceededScalingFactor { x: true, y: true })
);
}
#[test]
fn wrong_scaling_factor_x() {
let transform = [0.1, 0.0, MAX_SCALING_FACTOR_X.sqrt(), 0.0, 0.5, 0.0];
assert_eq!(
GeomPresTransform::try_from(transform),
Err(GeomPresTransformError::ExceededScalingFactor { x: true, y: false })
);
}
#[test]
fn wrong_scaling_factor_y() {
let transform = [0.0, MAX_SCALING_FACTOR_Y.sqrt(), 0.0, 0.1, 0.5, 0.0];
assert_eq!(
GeomPresTransform::try_from(transform),
Err(GeomPresTransformError::ExceededScalingFactor { x: false, y: true })
);
}
#[test]
fn correct_scaling_factor() {
let transform = [1.0, MAX_SCALING_FACTOR_Y.sqrt(), 0.0, 0.0, 0.5, 0.0];
assert_eq!(transform, GeomPresTransform::try_from(transform).unwrap().as_slice());
}
}