iced_graphics/
gradient.rs

1//! A gradient that can be used as a fill for some geometry.
2//!
3//! For a gradient that you can use as a background variant for a widget, see [`Gradient`].
4use crate::color;
5use crate::core::gradient::ColorStop;
6use crate::core::{self, Color, Point, Rectangle};
7
8use bytemuck::{Pod, Zeroable};
9use half::f16;
10use std::cmp::Ordering;
11
12#[derive(Debug, Clone, Copy, PartialEq)]
13/// A fill which linearly interpolates colors along a direction.
14///
15/// For a gradient which can be used as a fill for a background of a widget, see [`crate::core::Gradient`].
16pub enum Gradient {
17    /// A linear gradient interpolates colors along a direction from its `start` to its `end`
18    /// point.
19    Linear(Linear),
20}
21
22impl From<Linear> for Gradient {
23    fn from(gradient: Linear) -> Self {
24        Self::Linear(gradient)
25    }
26}
27
28impl Gradient {
29    /// Packs the [`Gradient`] for use in shader code.
30    pub fn pack(&self) -> Packed {
31        match self {
32            Gradient::Linear(linear) => linear.pack(),
33        }
34    }
35}
36
37/// A linear gradient.
38#[derive(Debug, Clone, Copy, PartialEq)]
39pub struct Linear {
40    /// The absolute starting position of the gradient.
41    pub start: Point,
42
43    /// The absolute ending position of the gradient.
44    pub end: Point,
45
46    /// [`ColorStop`]s along the linear gradient direction.
47    pub stops: [Option<ColorStop>; 8],
48}
49
50impl Linear {
51    /// Creates a new [`Linear`] builder.
52    pub fn new(start: Point, end: Point) -> Self {
53        Self {
54            start,
55            end,
56            stops: [None; 8],
57        }
58    }
59
60    /// Adds a new [`ColorStop`], defined by an offset and a color, to the gradient.
61    ///
62    /// Any `offset` that is not within `0.0..=1.0` will be silently ignored.
63    ///
64    /// Any stop added after the 8th will be silently ignored.
65    pub fn add_stop(mut self, offset: f32, color: Color) -> Self {
66        if offset.is_finite() && (0.0..=1.0).contains(&offset) {
67            let (Ok(index) | Err(index)) = self.stops.binary_search_by(|stop| match stop {
68                None => Ordering::Greater,
69                Some(stop) => stop.offset.partial_cmp(&offset).unwrap(),
70            });
71
72            if index < 8 {
73                self.stops[index] = Some(ColorStop { offset, color });
74            }
75        } else {
76            log::warn!("Gradient: ColorStop must be within 0.0..=1.0 range.");
77        };
78
79        self
80    }
81
82    /// Adds multiple [`ColorStop`]s to the gradient.
83    ///
84    /// Any stop added after the 8th will be silently ignored.
85    pub fn add_stops(mut self, stops: impl IntoIterator<Item = ColorStop>) -> Self {
86        for stop in stops {
87            self = self.add_stop(stop.offset, stop.color);
88        }
89
90        self
91    }
92
93    /// Packs the [`Gradient`] for use in shader code.
94    pub fn pack(&self) -> Packed {
95        let mut colors = [[0u32; 2]; 8];
96        let mut offsets = [f16::from(0u8); 8];
97
98        for (index, stop) in self.stops.iter().enumerate() {
99            let [r, g, b, a] = color::pack(stop.map_or(Color::default(), |s| s.color)).components();
100
101            colors[index] = [
102                pack_f16s([f16::from_f32(r), f16::from_f32(g)]),
103                pack_f16s([f16::from_f32(b), f16::from_f32(a)]),
104            ];
105
106            offsets[index] = stop.map_or(f16::from_f32(2.0), |s| f16::from_f32(s.offset));
107        }
108
109        let offsets = [
110            pack_f16s([offsets[0], offsets[1]]),
111            pack_f16s([offsets[2], offsets[3]]),
112            pack_f16s([offsets[4], offsets[5]]),
113            pack_f16s([offsets[6], offsets[7]]),
114        ];
115
116        let direction = [self.start.x, self.start.y, self.end.x, self.end.y];
117
118        Packed {
119            colors,
120            offsets,
121            direction,
122        }
123    }
124}
125
126/// Packed [`Gradient`] data for use in shader code.
127#[derive(Debug, Copy, Clone, PartialEq, Zeroable, Pod)]
128#[repr(C)]
129pub struct Packed {
130    // 8 colors, each channel = 16 bit float, 2 colors packed into 1 u32
131    colors: [[u32; 2]; 8],
132    // 8 offsets, 8x 16 bit floats packed into 4 u32s
133    offsets: [u32; 4],
134    direction: [f32; 4],
135}
136
137/// Creates a new [`Packed`] gradient for use in shader code.
138pub fn pack(gradient: &core::Gradient, bounds: Rectangle) -> Packed {
139    match gradient {
140        core::Gradient::Linear(linear) => {
141            let mut colors = [[0u32; 2]; 8];
142            let mut offsets = [f16::from(0u8); 8];
143
144            for (index, stop) in linear.stops.iter().enumerate() {
145                let [r, g, b, a] =
146                    color::pack(stop.map_or(Color::default(), |s| s.color)).components();
147
148                colors[index] = [
149                    pack_f16s([f16::from_f32(r), f16::from_f32(g)]),
150                    pack_f16s([f16::from_f32(b), f16::from_f32(a)]),
151                ];
152
153                offsets[index] = stop.map_or(f16::from_f32(2.0), |s| f16::from_f32(s.offset));
154            }
155
156            let offsets = [
157                pack_f16s([offsets[0], offsets[1]]),
158                pack_f16s([offsets[2], offsets[3]]),
159                pack_f16s([offsets[4], offsets[5]]),
160                pack_f16s([offsets[6], offsets[7]]),
161            ];
162
163            let (start, end) = linear.angle.to_distance(&bounds);
164
165            let direction = [start.x, start.y, end.x, end.y];
166
167            Packed {
168                colors,
169                offsets,
170                direction,
171            }
172        }
173    }
174}
175
176/// Packs two f16s into one u32.
177fn pack_f16s(f: [f16; 2]) -> u32 {
178    let one = (f[0].to_bits() as u32) << 16;
179    let two = f[1].to_bits() as u32;
180
181    one | two
182}
iced_graphics/gradient.rs

iced_graphics/
gradient.rs
