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//! Aspect ratio with transformed (log10) position scales.
//!
//! Both axes use a `log10` transform and the plot asks for
//! `aspect_ratio(1.0)`. For a transformed scale, aspect is measured in
//! *transformed* units, so `1.0` means **one decade on x occupies the
//! same screen distance as one decade on y** — regardless of where each
//! axis's raw range sits.
//!
//! The data traces the power law `y = x / 1000`. In log-log space that's
//! a straight line of slope 1, so it renders at exactly 45° *only* when
//! decades are square. x spans `[10, 10000]` (3 decades) and y spans
//! `[0.01, 10]` (3 decades) — wildly different raw ranges, identical
//! decade counts — and the line still comes out at 45° in both modes.
//!
//! ```text
//! ┌─────────────────────────┬─────────────────────────┐
//! │ log-log, AspectMode │ log-log, AspectMode │
//! │ ::Panel │ ::Range │
//! │ panel locked square, │ panel fills cell, x │
//! │ 45° slope-1 line │ range expanded, still │
//! │ │ 45° per-decade │
//! └─────────────────────────┴─────────────────────────┘
//! ```
//!
//! Writes `examples/aspect_log.png`.
use hephaestus::backend::vello::VelloRenderer;
use hephaestus::color::{rgb8, Color};
use hephaestus::composition::{grid, Composition, Patch};
use hephaestus::geometry::Size;
use hephaestus::plot::chrome::axis::{Axis, AxisPlacement};
use hephaestus::plot::{scale, AspectMode, LineGeom, Plot, PlotComposition, PointGeom};
use hephaestus::scales::chrome::AxisSide;
use hephaestus::scales::TransformKind;
use hephaestus::scene::SceneBuilder;
use hephaestus::Renderer;
fn comp_shape() -> Composition {
grid(
1,
2,
vec![
Patch::new("log_panel").into(),
Patch::new("log_range").into(),
],
)
}
fn main() {
// Markedly wide cells (a 1×2 grid in a wide viewport) so the two
// modes read differently: Panel locks the panel to a square with side
// slack, Range fills the cell — both keep decades square.
let (w, h) = (2000u32, 720u32);
let dpi = 96.0;
// Logarithmically spaced x over [10, 10000]; y = x / 1000 traces a
// slope-1 power law that fills y's [0.01, 10] range exactly.
let xs: Vec<f64> = (0..=60)
.map(|i| 10f64.powf(1.0 + 3.0 * (i as f64) / 60.0))
.collect();
let ys: Vec<f64> = xs.iter().map(|x| x / 1000.0).collect();
let line = rgb8(40, 90, 200);
let dot = rgb8(200, 60, 40);
let mut view = PlotComposition::new(&comp_shape())
.add_scale(
"x",
scale::continuous(10.0..=10000.0).with_transform(TransformKind::Log10),
)
.add_scale(
"y",
scale::continuous(0.01..=10.0).with_transform(TransformKind::Log10),
);
// ── Panel mode (the default).
// Equal transformed extents (3 decades each) plus `aspect_ratio(1.0)`
// lock the panel to a square; the slope-1 line lands at 45°.
{
let mut p = Plot::new(&comp_shape(), "log_panel")
.title("log-log · AspectMode::Panel")
.subtitle("panel locked square, one decade square on both axes")
.bind("x", "x")
.bind("y", "y")
.aspect_ratio(1.0);
p.add_geom(
LineGeom::builder()
.set("x", xs.clone())
.set("y", ys.clone())
.set("stroke", line)
.set("linewidth", 1.5_f64)
.build(),
);
p.add_geom(
PointGeom::builder()
.set("x", xs.clone())
.set("y", ys.clone())
.set("fill", dot)
.set("size", 4.0_f64)
.build(),
);
p.add_axis(Axis::rail("x", AxisPlacement::Cartesian(AxisSide::Bottom)));
p.add_axis(Axis::rail("y", AxisPlacement::Cartesian(AxisSide::Left)));
view.attach_plot(p);
}
// ── Range mode.
// Same `aspect_ratio(1.0)`, but the panel fills the wide cell. The x
// scale's range is expanded *in log space* to keep decades square, so
// the slope-1 line stays at 45°; the bottom axis shows the widened
// decade range.
{
let mut p = Plot::new(&comp_shape(), "log_range")
.title("log-log · AspectMode::Range")
.subtitle("panel fills cell, x range expanded in log space")
.bind("x", "x")
.bind("y", "y")
.aspect_ratio(1.0)
.aspect_mode(AspectMode::Range);
p.add_geom(
LineGeom::builder()
.set("x", xs.clone())
.set("y", ys.clone())
.set("stroke", line)
.set("linewidth", 1.5_f64)
.build(),
);
p.add_geom(
PointGeom::builder()
.set("x", xs.clone())
.set("y", ys.clone())
.set("fill", dot)
.set("size", 4.0_f64)
.build(),
);
p.add_axis(Axis::rail("x", AxisPlacement::Cartesian(AxisSide::Bottom)));
p.add_axis(Axis::rail("y", AxisPlacement::Cartesian(AxisSide::Left)));
view.attach_plot(p);
}
let issues = view.validate();
if !issues.is_empty() {
panic!("validate() reported issues: {issues:?}");
}
let mut renderer = VelloRenderer::new().expect("vello renderer init");
let bg: Color = rgb8(248, 248, 252);
{
let scene = renderer.scene();
scene.clear();
view.render(scene, Size::new(w as f64, h as f64), dpi);
}
let mut pixels = vec![0u8; (w * h * 4) as usize];
renderer
.render_to_buffer(w, h, bg, &mut pixels)
.expect("render");
let path = std::env::current_dir()
.unwrap()
.join("examples/aspect_log.png");
hephaestus::image::write_png(&path, w, h, &pixels).expect("write png");
println!("wrote {}", path.display());
}