ggplot_rs/geom/
area.rs

1use crate::aes::Aesthetic;
2use crate::coord::Coord;
3use crate::data::{DataFrame, Value};
4use crate::position::stack::PositionStack;
5use crate::position::Position;
6use crate::render::backend::{DrawBackend, LineStyle, Linetype, RectStyle};
7use crate::render::RenderError;
8use crate::scale::ScaleSet;
9use crate::stat::align::StatAlign;
10use crate::stat::Stat;
11use crate::theme::Theme;
12
13use super::{Geom, GeomParams};
14
15/// Area geometry — filled polygon from line to x-axis baseline.
16pub struct GeomArea {
17    pub fill: (u8, u8, u8),
18    pub color: (u8, u8, u8),
19    pub alpha: f64,
20    pub line_width: f64,
21    /// How consecutive points are joined (straight by default; a smooth
22    /// `areaspline` with [`Interpolate::MonotoneCubic`](super::support::Interpolate::MonotoneCubic)).
23    pub interpolate: super::support::Interpolate,
24}
25
26impl Default for GeomArea {
27    fn default() -> Self {
28        GeomArea {
29            fill: (97, 156, 255),
30            color: (50, 50, 50),
31            alpha: 0.4,
32            line_width: 1.0,
33            interpolate: super::support::Interpolate::Linear,
34        }
35    }
36}
37
38impl Geom for GeomArea {
39    fn key_fill(&self) -> Option<((u8, u8, u8), f64)> {
40        Some((self.fill, self.alpha))
41    }
42
43    fn draw(
44        &self,
45        data: &DataFrame,
46        coord: &dyn Coord,
47        scales: &ScaleSet,
48        _theme: &Theme,
49        backend: &mut dyn DrawBackend,
50    ) -> Result<(), RenderError> {
51        let x_col = data
52            .column("x")
53            .ok_or(RenderError::MissingAesthetic("x".into()))?;
54        let y_col = data
55            .column("y")
56            .ok_or(RenderError::MissingAesthetic("y".into()))?;
57
58        // A fill/color aesthetic (or an explicit group) splits the data into one
59        // filled band per series — as in a grouped or stacked area chart.
60        let group_col = data
61            .column("fill")
62            .or_else(|| data.column("color"))
63            .or_else(|| data.column("group"));
64        // `ymin` is set by position="stack"/"fill" (the bottom of each segment);
65        // without it the band runs from the y=0 baseline.
66        let ymin_col = data.column("ymin");
67
68        let plot_area = backend.plot_area();
69        let x_scale = scales.get(&Aesthetic::X);
70        let y_scale = scales.get(&Aesthetic::Y);
71        let base_ny = y_scale.map(|s| s.map(&Value::Float(0.0))).unwrap_or(0.0);
72
73        // Group row indices by the series key, preserving first-seen order (which
74        // is the stacking order the position adjustment produced).
75        let mut groups: Vec<(String, Vec<usize>)> = Vec::new();
76        match group_col {
77            Some(gc) => {
78                for (i, v) in gc.iter().enumerate() {
79                    let key = v.to_group_key();
80                    match groups.iter_mut().find(|(k, _)| k == &key) {
81                        Some((_, idx)) => idx.push(i),
82                        None => groups.push((key, vec![i])),
83                    }
84                }
85            }
86            None => groups.push((String::new(), (0..data.nrows()).collect())),
87        }
88
89        for (_, indices) in &groups {
90            // Order this series left-to-right so the band is a clean polygon.
91            let mut idx = indices.clone();
92            idx.sort_by(|&a, &b| {
93                let xa = x_scale.map(|s| s.map(&x_col[a])).unwrap_or(0.0);
94                let xb = x_scale.map(|s| s.map(&x_col[b])).unwrap_or(0.0);
95                xa.total_cmp(&xb)
96            });
97
98            let fill = group_col
99                .and_then(|gc| scales.map_color(&Aesthetic::Fill, &gc[idx[0]]))
100                .or_else(|| {
101                    group_col.and_then(|gc| scales.map_color(&Aesthetic::Color, &gc[idx[0]]))
102                })
103                .unwrap_or(self.fill);
104
105            let mut upper_raw: Vec<(f64, f64)> = Vec::with_capacity(idx.len());
106            let mut lower_raw: Vec<(f64, f64)> = Vec::with_capacity(idx.len());
107            for &i in &idx {
108                let nx = x_scale.map(|s| s.map(&x_col[i])).unwrap_or(0.0);
109                let ny = y_scale.map(|s| s.map(&y_col[i])).unwrap_or(0.0);
110                let nb = ymin_col
111                    .and_then(|c| c[i].as_f64())
112                    .and_then(|v| y_scale.map(|s| s.map(&Value::Float(v))))
113                    .unwrap_or(base_ny);
114                upper_raw.push((nx, ny));
115                lower_raw.push((nx, nb));
116            }
117            let to_px = |pts: Vec<(f64, f64)>| -> Vec<(f64, f64)> {
118                super::support::interpolate(&pts, self.interpolate)
119                    .0
120                    .into_iter()
121                    .map(|p| coord.transform(p, &plot_area))
122                    .collect()
123            };
124            let (upper, mut lower) = (to_px(upper_raw), to_px(lower_raw));
125
126            let mut polygon = upper.clone();
127            lower.reverse();
128            polygon.extend(lower);
129            if polygon.len() >= 3 {
130                backend.draw_polygon(
131                    &polygon,
132                    &RectStyle {
133                        fill: Some(fill),
134                        stroke: None,
135                        stroke_width: 0.0,
136                        alpha: self.alpha,
137                        clip: true,
138                        corner_radius: 0.0,
139                    },
140                )?;
141            }
142            if upper.len() >= 2 {
143                // A single-series area keeps its dark outline; multi-series bands
144                // outline in their own fill so stacked bands stay legible.
145                let line_color = if groups.len() > 1 { fill } else { self.color };
146                backend.draw_line(
147                    &upper,
148                    &LineStyle {
149                        color: line_color,
150                        alpha: 1.0,
151                        width: self.line_width,
152                        linetype: Linetype::Solid,
153                        ..Default::default()
154                    },
155                )?;
156            }
157        }
158
159        Ok(())
160    }
161
162    fn required_aes(&self) -> Vec<Aesthetic> {
163        vec![Aesthetic::X, Aesthetic::Y]
164    }
165
166    fn default_stat(&self) -> Box<dyn Stat> {
167        // ggplot2 parity (#172): `geom_area()`'s default stat is
168        // `stat_align()`, so series sampled at different x stack without
169        // dipping where one has no row.
170        Box::new(StatAlign)
171    }
172    fn default_position(&self) -> Box<dyn Position> {
173        // ggplot2 parity (sipemu/ggplot-rs#171 review finding 5): `geom_area()`
174        // defaults to `position_stack()`, same as `geom_col()`/`geom_bar()`
175        // (#169, just above those geoms' own `default_position`). 0.23/0.24
176        // left this as `PositionIdentity`, the same gap #169 fixed for
177        // `geom_col()` — landing it in the same minor as #169 so every
178        // default-position parity break is in one release.
179        Box::new(PositionStack)
180    }
181    fn default_params(&self) -> GeomParams {
182        GeomParams::default()
183    }
184    fn name(&self) -> &str {
185        "area"
186    }
187
188    fn apply_element_geom(&mut self, el: &crate::theme::elements::ElementGeom) {
189        if let (true, Some(ink)) = (self.color == (50, 50, 50), el.ink) {
190            self.color = ink;
191        }
192    }
193
194    fn include_zero_baseline(&self) -> bool {
195        true
196    }
197
198    fn set_series_color(&mut self, color: (u8, u8, u8)) {
199        self.fill = color;
200    }
201}
ggplot_rs/geom/area.rs

ggplot_rs/geom/
area.rs
