1use crate::{
2 element::{Drawable, PointCollection},
3 style::{IntoFont, RGBColor, TextStyle, BLACK},
4};
5use plotters_backend::{BackendCoord, DrawingBackend, DrawingErrorKind};
6use std::{error::Error, f64::consts::PI, fmt::Display};
7
8#[derive(Debug)]
9enum PieError {
10 LengthMismatch,
11}
12impl Display for PieError {
13 fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
14 match self {
15 &PieError::LengthMismatch => write!(f, "Length Mismatch"),
16 }
17 }
18}
19
20impl Error for PieError {}
21
22/// A Pie Graph
23pub struct Pie<'a, Coord, Label: Display> {
24 center: &'a Coord, // cartesian coord
25 radius: &'a f64,
26 sizes: &'a [f64],
27 colors: &'a [RGBColor],
28 labels: &'a [Label],
29 total: f64,
30 start_radian: f64,
31 label_style: TextStyle<'a>,
32 label_offset: f64,
33 percentage_style: Option<TextStyle<'a>>,
34}
35
36impl<'a, Label: Display> Pie<'a, (i32, i32), Label> {
37 /// Build a Pie object.
38 /// Assumes a start angle at 0.0, which is aligned to the horizontal axis.
39 pub fn new(
40 center: &'a (i32, i32),
41 radius: &'a f64,
42 sizes: &'a [f64],
43 colors: &'a [RGBColor],
44 labels: &'a [Label],
45 ) -> Self {
46 // fold iterator to pre-calculate total from given slice sizes
47 let total = sizes.iter().sum();
48
49 // default label style and offset as 5% of the radius
50 let radius_5pct = radius * 0.05;
51
52 // strong assumption that the background is white for legibility.
53 let label_style = TextStyle::from(("sans-serif", radius_5pct).into_font()).color(&BLACK);
54 Self {
55 center,
56 radius,
57 sizes,
58 colors,
59 labels,
60 total,
61 start_radian: 0.0,
62 label_style,
63 label_offset: radius_5pct,
64 percentage_style: None,
65 }
66 }
67
68 /// Pass an angle in degrees to change the default.
69 /// Default is set to start at 0, which is aligned on the x axis.
70 /// ```
71 /// use plotters::prelude::*;
72 /// let mut pie = Pie::new(&(50,50), &10.0, &[50.0, 25.25, 20.0, 5.5], &[RED, BLUE, GREEN, WHITE], &["Red", "Blue", "Green", "White"]);
73 /// pie.start_angle(-90.0); // retract to a right angle, so it starts aligned to a vertical Y axis.
74 /// ```
75 pub fn start_angle(&mut self, start_angle: f64) {
76 // angle is more intuitive in degrees as an API, but we use it as radian offset internally.
77 self.start_radian = start_angle.to_radians();
78 }
79
80 ///
81 pub fn label_style<T: Into<TextStyle<'a>>>(&mut self, label_style: T) {
82 self.label_style = label_style.into();
83 }
84
85 /// Sets the offset to labels, to distanciate them further/closer from the center.
86 pub fn label_offset(&mut self, offset_to_radius: f64) {
87 self.label_offset = offset_to_radius
88 }
89
90 /// enables drawing the wedge's percentage in the middle of the wedge, with the given style
91 pub fn percentages<T: Into<TextStyle<'a>>>(&mut self, label_style: T) {
92 self.percentage_style = Some(label_style.into());
93 }
94}
95
96impl<'a, DB: DrawingBackend, Label: Display> Drawable<DB> for Pie<'a, (i32, i32), Label> {
97 fn draw<I: Iterator<Item = BackendCoord>>(
98 &self,
99 _pos: I,
100 backend: &mut DB,
101 _parent_dim: (u32, u32),
102 ) -> Result<(), DrawingErrorKind<DB::ErrorType>> {
103 let mut offset_theta = self.start_radian;
104
105 // const reused for every radian calculation
106 // the bigger the radius, the more fine-grained it should calculate
107 // to avoid being aliasing from being too noticeable.
108 // this all could be avoided if backend could draw a curve/bezier line as part of a polygon.
109 let radian_increment = PI / 180.0 / self.radius.sqrt() * 2.0;
110 let mut perc_labels = Vec::new();
111 for (index, slice) in self.sizes.iter().enumerate() {
112 let slice_style = self
113 .colors
114 .get(index)
115 .ok_or_else(|| DrawingErrorKind::FontError(Box::new(PieError::LengthMismatch)))?;
116 let label = self
117 .labels
118 .get(index)
119 .ok_or_else(|| DrawingErrorKind::FontError(Box::new(PieError::LengthMismatch)))?;
120 // start building wedge line against the previous edge
121 let mut points = vec![*self.center];
122 let ratio = slice / self.total;
123 let theta_final = ratio * 2.0 * PI + offset_theta; // end radian for the wedge
124
125 // calculate middle for labels before mutating offset
126 let middle_theta = ratio * PI + offset_theta;
127
128 // calculate every fraction of radian for the wedge, offsetting for every iteration, clockwise
129 //
130 // a custom Range such as `for theta in offset_theta..=theta_final` would be more elegant
131 // but f64 doesn't implement the Range trait, and it would requires the Step trait (increment by 1.0 or 0.0001?)
132 // which is unstable therefore cannot be implemented outside of std, even as a newtype for radians.
133 while offset_theta <= theta_final {
134 let coord = theta_to_ordinal_coord(*self.radius, offset_theta, self.center);
135 points.push(coord);
136 offset_theta += radian_increment;
137 }
138 // final point of the wedge may not fall exactly on a radian, so add it extra
139 let final_coord = theta_to_ordinal_coord(*self.radius, theta_final, self.center);
140 points.push(final_coord);
141 // next wedge calculation will start from previous wedges's last radian
142 offset_theta = theta_final;
143
144 // draw wedge
145 // TODO: Currently the backend doesn't have API to draw an arc. We need add that in the
146 // future
147 backend.fill_polygon(points, slice_style)?;
148
149 // label coords from the middle
150 let mut mid_coord =
151 theta_to_ordinal_coord(self.radius + self.label_offset, middle_theta, self.center);
152
153 // ensure label's doesn't fall in the circle
154 let label_size = backend.estimate_text_size(&label.to_string(), &self.label_style)?;
155 // if on the left hand side of the pie, offset whole label to the left
156 if mid_coord.0 <= self.center.0 {
157 mid_coord.0 -= label_size.0 as i32;
158 }
159 // put label
160 backend.draw_text(&label.to_string(), &self.label_style, mid_coord)?;
161 if let Some(percentage_style) = &self.percentage_style {
162 let perc_label = format!("{:.1}%", (ratio * 100.0));
163 let label_size = backend.estimate_text_size(&perc_label, percentage_style)?;
164 let text_x_mid = (label_size.0 as f64 / 2.0).round() as i32;
165 let text_y_mid = (label_size.1 as f64 / 2.0).round() as i32;
166 let perc_coord = theta_to_ordinal_coord(
167 self.radius / 2.0,
168 middle_theta,
169 &(self.center.0 - text_x_mid, self.center.1 - text_y_mid),
170 );
171 // perc_coord.0 -= middle_label_size.0.round() as i32;
172 perc_labels.push((perc_label, perc_coord));
173 }
174 }
175 // while percentages are generated during the first main iterations,
176 // they have to go on top of the already drawn wedges, so require a new iteration.
177 for (label, coord) in perc_labels {
178 let style = self.percentage_style.as_ref().unwrap();
179 backend.draw_text(&label, style, coord)?;
180 }
181 Ok(())
182 }
183}
184
185impl<'a, Label: Display> PointCollection<'a, (i32, i32)> for &'a Pie<'a, (i32, i32), Label> {
186 type Point = &'a (i32, i32);
187 type IntoIter = std::iter::Once<&'a (i32, i32)>;
188 fn point_iter(self) -> std::iter::Once<&'a (i32, i32)> {
189 std::iter::once(self.center)
190 }
191}
192
193fn theta_to_ordinal_coord(radius: f64, theta: f64, ordinal_offset: &(i32, i32)) -> (i32, i32) {
194 // polar coordinates are (r, theta)
195 // convert to (x, y) coord, with center as offset
196
197 let (sin, cos) = theta.sin_cos();
198 (
199 // casting f64 to discrete i32 pixels coordinates is inevitably going to lose precision
200 // if plotters can support float coordinates, this place would surely benefit, especially for small sizes.
201 // so far, the result isn't so bad though
202 (radius * cos + ordinal_offset.0 as f64).round() as i32, // x
203 (radius * sin + ordinal_offset.1 as f64).round() as i32, // y
204 )
205}
206#[cfg(test)]
207mod test {
208 use super::*;
209 // use crate::prelude::*;
210
211 #[test]
212 fn polar_coord_to_cartestian_coord() {
213 let coord = theta_to_ordinal_coord(800.0, 1.5_f64.to_radians(), &(5, 5));
214 // rounded tends to be more accurate. this gets truncated to (804, 25) without rounding.
215 assert_eq!(coord, (805, 26)); //coord calculated from theta
216 }
217 #[test]
218 fn pie_calculations() {
219 let mut center = (5, 5);
220 let mut radius = 800.0;
221
222 let sizes = vec![50.0, 25.0];
223 // length isn't validated in new()
224 let colors = vec![];
225 let labels: Vec<&str> = vec![];
226 let pie = Pie::new(&center, &radius, &sizes, &colors, &labels);
227 assert_eq!(pie.total, 75.0); // total calculated from sizes
228
229 // not ownership greedy
230 center.1 += 1;
231 radius += 1.0;
232 assert!(colors.get(0).is_none());
233 assert!(labels.get(0).is_none());
234 assert_eq!(radius, 801.0);
235 }
236}
237