surpass/
transform.rs

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
// 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::error::Error;
use std::fmt;

use crate::path::MAX_ERROR;
use crate::{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());
    }
}