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Customize grid spacing in plots (#1180)

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This commit is contained in:
Jan Haller
2022-04-19 11:35:05 +02:00
committed by GitHub
parent 676ff047e9
commit e22f6d9a7e
3 changed files with 305 additions and 50 deletions
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200
egui/src/widgets/plot/mod.rs
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@@ -6,6 +6,7 @@ use crate::*;
use epaint::ahash::AHashSet;
use epaint::color::Hsva;
use epaint::util::FloatOrd;
use items::PlotItem;
use legend::LegendWidget;
use transform::ScreenTransform;
@@ -26,6 +27,9 @@ type LabelFormatter = Option<Box<LabelFormatterFn>>;
type AxisFormatterFn = dyn Fn(f64, &RangeInclusive<f64>) -> String;
type AxisFormatter = Option<Box<AxisFormatterFn>>;
type GridSpacerFn = dyn Fn(GridInput) -> Vec<GridMark>;
type GridSpacer = Box<GridSpacerFn>;
/// Specifies the coordinates formatting when passed to [`Plot::coordinates_formatter`].
pub struct CoordinatesFormatter {
function: Box<dyn Fn(&Value, &PlotBounds) -> String>,
@@ -61,6 +65,8 @@ impl Default for CoordinatesFormatter {
// ----------------------------------------------------------------------------
const MIN_LINE_SPACING_IN_POINTS: f64 = 6.0; // TODO: large enough for a wide label
/// Information about the plot that has to persist between frames.
#[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
#[derive(Clone)]
@@ -186,6 +192,7 @@ pub struct Plot {
legend_config: Option<Legend>,
show_background: bool,
show_axes: [bool; 2],
grid_spacers: [GridSpacer; 2],
}
impl Plot {
@@ -219,6 +226,7 @@ impl Plot {
legend_config: None,
show_background: true,
show_axes: [true; 2],
grid_spacers: [log_grid_spacer(10), log_grid_spacer(10)],
}
}
@@ -393,6 +401,49 @@ impl Plot {
self
}
/// Configure how the grid in the background is spaced apart along the X axis.
///
/// Default is a log-10 grid, i.e. every plot unit is divided into 10 other units.
///
/// The function has this signature:
/// ```ignore
/// fn get_step_sizes(input: GridInput) -> Vec<GridMark>;
/// ```
///
/// This function should return all marks along the visible range of the X axis.
/// `step_size` also determines how thick/faint each line is drawn.
/// For example, if x = 80..=230 is visible and you want big marks at steps of
/// 100 and small ones at 25, you can return:
/// ```no_run
/// # use egui::plot::GridMark;
/// vec![
/// // 100s
/// GridMark { value: 100.0, step_size: 100.0 },
/// GridMark { value: 200.0, step_size: 100.0 },
///
/// // 25s
/// GridMark { value: 125.0, step_size: 25.0 },
/// GridMark { value: 150.0, step_size: 25.0 },
/// GridMark { value: 175.0, step_size: 25.0 },
/// GridMark { value: 225.0, step_size: 25.0 },
/// ];
/// # ()
/// ```
///
/// There are helpers for common cases, see [`log_grid_spacer`] and [`uniform_grid_spacer`].
pub fn x_grid_spacer(mut self, spacer: impl Fn(GridInput) -> Vec<GridMark> + 'static) -> Self {
self.grid_spacers[0] = Box::new(spacer);
self
}
/// Default is a log-10 grid, i.e. every plot unit is divided into 10 other units.
///
/// See [`Self::x_grid_spacer`] for explanation.
pub fn y_grid_spacer(mut self, spacer: impl Fn(GridInput) -> Vec<GridMark> + 'static) -> Self {
self.grid_spacers[1] = Box::new(spacer);
self
}
/// Expand bounds to include the given x value.
/// For instance, to always show the y axis, call `plot.include_x(0.0)`.
pub fn include_x(mut self, x: impl Into<f64>) -> Self {
@@ -463,6 +514,7 @@ impl Plot {
show_background,
show_axes,
linked_axes,
grid_spacers,
} = self;
// Determine the size of the plot in the UI
@@ -706,6 +758,7 @@ impl Plot {
axis_formatters,
show_axes,
transform: transform.clone(),
grid_spacers,
};
prepared.ui(ui, &response);
@@ -922,6 +975,80 @@ impl PlotUi {
}
}
// ----------------------------------------------------------------------------
// Grid
/// Input for "grid spacer" functions.
///
/// See [`Plot::x_grid_spacer()`] and [`Plot::y_grid_spacer()`].
pub struct GridInput {
/// Min/max of the visible data range (the values at the two edges of the plot,
/// for the current axis).
pub bounds: (f64, f64),
/// Recommended (but not required) lower-bound on the step size returned by custom grid spacers.
///
/// Computed as the ratio between the diagram's bounds (in plot coordinates) and the viewport
/// (in frame/window coordinates), scaled up to represent the minimal possible step.
pub base_step_size: f64,
}
/// One mark (horizontal or vertical line) in the background grid of a plot.
pub struct GridMark {
/// X or Y value in the plot.
pub value: f64,
/// The (approximate) distance to the next value of same thickness.
///
/// Determines how thick the grid line is painted. It's not important that `step_size`
/// matches the difference between two `value`s precisely, but rather that grid marks of
/// same thickness have same `step_size`. For example, months can have a different number
/// of days, but consistently using a `step_size` of 30 days is a valid approximation.
pub step_size: f64,
}
/// Recursively splits the grid into `base` subdivisions (e.g. 100, 10, 1).
///
/// The logarithmic base, expressing how many times each grid unit is subdivided.
/// 10 is a typical value, others are possible though.
pub fn log_grid_spacer(log_base: i64) -> GridSpacer {
let log_base = log_base as f64;
let get_step_sizes = move |input: GridInput| -> Vec<GridMark> {
// The distance between two of the thinnest grid lines is "rounded" up
// to the next-bigger power of base
let smallest_visible_unit = next_power(input.base_step_size, log_base);
let step_sizes = [
smallest_visible_unit,
smallest_visible_unit * log_base,
smallest_visible_unit * log_base * log_base,
];
generate_marks(step_sizes, input.bounds)
};
Box::new(get_step_sizes)
}
/// Splits the grid into uniform-sized spacings (e.g. 100, 25, 1).
///
/// This function should return 3 positive step sizes, designating where the lines in the grid are drawn.
/// Lines are thicker for larger step sizes. Ordering of returned value is irrelevant.
///
/// Why only 3 step sizes? Three is the number of different line thicknesses that egui typically uses in the grid.
/// Ideally, those 3 are not hardcoded values, but depend on the visible range (accessible through `GridInput`).
pub fn uniform_grid_spacer(spacer: impl Fn(GridInput) -> [f64; 3] + 'static) -> GridSpacer {
let get_marks = move |input: GridInput| -> Vec<GridMark> {
let bounds = input.bounds;
let step_sizes = spacer(input);
generate_marks(step_sizes, bounds)
};
Box::new(get_marks)
}
// ----------------------------------------------------------------------------
struct PreparedPlot {
items: Vec<Box<dyn PlotItem>>,
show_x: bool,
@@ -931,6 +1058,7 @@ struct PreparedPlot {
axis_formatters: [AxisFormatter; 2],
show_axes: [bool; 2],
transform: ScreenTransform,
grid_spacers: [GridSpacer; 2],
}
impl PreparedPlot {
@@ -979,6 +1107,7 @@ impl PreparedPlot {
let Self {
transform,
axis_formatters,
grid_spacers,
..
} = self;
@@ -991,43 +1120,31 @@ impl PreparedPlot {
let font_id = TextStyle::Body.resolve(ui.style());
let base: i64 = 10;
let basef = base as f64;
let min_line_spacing_in_points = 6.0; // TODO: large enough for a wide label
let step_size = transform.dvalue_dpos()[axis] * min_line_spacing_in_points;
let step_size = basef.powi(step_size.abs().log(basef).ceil() as i32);
let step_size_in_points = (transform.dpos_dvalue()[axis] * step_size).abs() as f32;
// Where on the cross-dimension to show the label values
let bounds = transform.bounds();
let value_cross = 0.0_f64.clamp(bounds.min[1 - axis], bounds.max[1 - axis]);
for i in 0.. {
let value_main = step_size * (bounds.min[axis] / step_size + i as f64).floor();
if value_main > bounds.max[axis] {
break;
}
let input = GridInput {
bounds: (bounds.min[axis], bounds.max[axis]),
base_step_size: transform.dvalue_dpos()[axis] * MIN_LINE_SPACING_IN_POINTS,
};
let steps = (grid_spacers[axis])(input);
for step in steps {
let value_main = step.value;
let value = if axis == 0 {
Value::new(value_main, value_cross)
} else {
Value::new(value_cross, value_main)
};
let pos_in_gui = transform.position_from_value(&value);
let n = (value_main / step_size).round() as i64;
let spacing_in_points = if n % (base * base) == 0 {
step_size_in_points * (basef * basef) as f32 // think line (multiple of 100)
} else if n % base == 0 {
step_size_in_points * basef as f32 // medium line (multiple of 10)
} else {
step_size_in_points // thin line
};
let pos_in_gui = transform.position_from_value(&value);
let spacing_in_points = (transform.dpos_dvalue()[axis] * step.step_size).abs() as f32;
let line_alpha = remap_clamp(
spacing_in_points,
(min_line_spacing_in_points as f32)..=300.0,
(MIN_LINE_SPACING_IN_POINTS as f32)..=300.0,
0.0..=0.15,
);
@@ -1119,3 +1236,38 @@ impl PreparedPlot {
}
}
}
/// Returns next bigger power in given base
/// e.g.
/// ```ignore
/// use egui::plot::next_power;
/// assert_eq!(next_power(0.01, 10.0), 0.01);
/// assert_eq!(next_power(0.02, 10.0), 0.1);
/// assert_eq!(next_power(0.2, 10.0), 1);
/// ```
fn next_power(value: f64, base: f64) -> f64 {
assert_ne!(value, 0.0); // can be negative (typical for Y axis)
base.powi(value.abs().log(base).ceil() as i32)
}
/// Fill in all values between [min, max] which are a multiple of `step_size`
fn generate_marks(step_sizes: [f64; 3], bounds: (f64, f64)) -> Vec<GridMark> {
let mut steps = vec![];
fill_marks_between(&mut steps, step_sizes[0], bounds);
fill_marks_between(&mut steps, step_sizes[1], bounds);
fill_marks_between(&mut steps, step_sizes[2], bounds);
steps
}
/// Fill in all values between [min, max] which are a multiple of `step_size`
fn fill_marks_between(out: &mut Vec<GridMark>, step_size: f64, (min, max): (f64, f64)) {
assert!(max > min);
let first = (min / step_size).ceil() as i64;
let last = (max / step_size).ceil() as i64;
let marks_iter = (first..last).map(|i| {
let value = (i as f64) * step_size;
GridMark { value, step_size }
});
out.extend(marks_iter);
}