Add bar charts and box plots (#863)

Changes:
* New `BarChart` and `BoxPlot` diagrams
* New `FloatOrd` trait for total ordering of float types
* Refactoring of existing plot items

Co-authored-by: niladic <git@nil.choron.cc>

CHANGELOG.md

@@ -8,6 +8,7 @@ NOTE: [`epaint`](epaint/CHANGELOG.md), [`eframe`](eframe/CHANGELOG.md), [`egui_w
 ## Unreleased
 
 ### Added ⭐
+* Add bar charts and box plots ([#863](https://github.com/emilk/egui/pull/863)).
 * Add context menus: See `Ui::menu_button` and `Response::context_menu` ([#543](https://github.com/emilk/egui/pull/543)).
 * You can now read and write the cursor of a `TextEdit` ([#848](https://github.com/emilk/egui/pull/848)).
 * Most widgets containing text (`Label`, `Button` etc) now supports rich text ([#855](https://github.com/emilk/egui/pull/855)).

egui/src/util/float_ord.rs

@@ -0,0 +1,64 @@
+//! Total order on floating point types, assuming absence of NaN.
+//! Can be used for sorting, min/max computation, and other collection algorithms.
+
+use std::cmp::Ordering;
+
+/// Totally orderable floating-point value
+/// For not `f32` is supported; could be made generic if necessary.
+pub(crate) struct OrderedFloat(f32);
+
+impl Eq for OrderedFloat {}
+
+impl PartialEq<Self> for OrderedFloat {
+    #[inline]
+    fn eq(&self, other: &Self) -> bool {
+        // NaNs are considered equal (equivalent when it comes to ordering
+        if self.0.is_nan() {
+            other.0.is_nan()
+        } else {
+            self.0 == other.0
+        }
+    }
+}
+
+impl PartialOrd<Self> for OrderedFloat {
+    #[inline]
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        match self.0.partial_cmp(&other.0) {
+            Some(ord) => Some(ord),
+            None => Some(self.0.is_nan().cmp(&other.0.is_nan())),
+        }
+    }
+}
+
+impl Ord for OrderedFloat {
+    #[inline]
+    fn cmp(&self, other: &Self) -> Ordering {
+        match self.partial_cmp(other) {
+            Some(ord) => ord,
+            None => unreachable!(),
+        }
+    }
+}
+
+/// Extension trait to provide `ord` method
+pub(crate) trait FloatOrd {
+    /// Type to provide total order, useful as key in sorted contexts.
+    fn ord(self) -> OrderedFloat;
+}
+
+impl FloatOrd for f32 {
+    #[inline]
+    fn ord(self) -> OrderedFloat {
+        OrderedFloat(self)
+    }
+}
+
+// TODO ordering may break down at least significant digits due to f64 -> f32 conversion
+// Possible solutions: generic OrderedFloat<T>, always OrderedFloat(f64)
+impl FloatOrd for f64 {
+    #[inline]
+    fn ord(self) -> OrderedFloat {
+        OrderedFloat(self as f32)
+    }
+}

egui/src/util/mod.rs

@@ -2,6 +2,7 @@
 
 pub mod cache;
 pub(crate) mod fixed_cache;
+pub(crate) mod float_ord;
 mod history;
 pub mod id_type_map;
 pub mod undoer;

egui/src/widgets/plot/items/bar.rs

@@ -0,0 +1,190 @@
+use crate::emath::NumExt;
+use crate::epaint::{Color32, RectShape, Shape, Stroke};
+
+use super::{add_rulers_and_text, highlighted_color, Orientation, PlotConfig, RectElement};
+use crate::plot::{BarChart, ScreenTransform, Value};
+
+/// One bar in a [`BarChart`]. Potentially floating, allowing stacked bar charts.
+/// Width can be changed to allow variable-width histograms.
+#[derive(Clone, Debug, PartialEq)]
+pub struct Bar {
+    /// Name of plot element in the diagram (annotated by default formatter)
+    pub name: String,
+
+    /// Which direction the bar faces in the diagram
+    pub orientation: Orientation,
+
+    /// Position on the argument (input) axis -- X if vertical, Y if horizontal
+    pub argument: f64,
+
+    /// Position on the value (output) axis -- Y if vertical, X if horizontal
+    pub value: f64,
+
+    /// For stacked bars, this denotes where the bar starts. None if base axis
+    pub base_offset: Option<f64>,
+
+    /// Thickness of the bar
+    pub bar_width: f64,
+
+    /// Line width and color
+    pub stroke: Stroke,
+
+    /// Fill color
+    pub fill: Color32,
+}
+
+impl Bar {
+    /// Create a bar. Its `orientation` is set by its [`BarChart`] parent.
+    ///
+    /// - `argument`: Position on the argument axis (X if vertical, Y if horizontal).
+    /// - `value`: Height of the bar (if vertical).
+    ///
+    /// By default the bar is vertical and its base is at zero.
+    pub fn new(argument: f64, height: f64) -> Bar {
+        Bar {
+            argument,
+            value: height,
+            orientation: Orientation::default(),
+            name: Default::default(),
+            base_offset: None,
+            bar_width: 0.5,
+            stroke: Stroke::new(1.0, Color32::TRANSPARENT),
+            fill: Color32::TRANSPARENT,
+        }
+    }
+
+    /// Name of this bar chart element.
+    #[allow(clippy::needless_pass_by_value)]
+    pub fn name(mut self, name: impl ToString) -> Self {
+        self.name = name.to_string();
+        self
+    }
+
+    /// Add a custom stroke.
+    pub fn stroke(mut self, stroke: impl Into<Stroke>) -> Self {
+        self.stroke = stroke.into();
+        self
+    }
+
+    /// Add a custom fill color.
+    pub fn fill(mut self, color: impl Into<Color32>) -> Self {
+        self.fill = color.into();
+        self
+    }
+
+    /// Offset the base of the bar.
+    /// This offset is on the Y axis for a vertical bar
+    /// and on the X axis for a horizontal bar.
+    pub fn base_offset(mut self, offset: f64) -> Self {
+        self.base_offset = Some(offset);
+        self
+    }
+
+    /// Set the bar width.
+    pub fn width(mut self, width: f64) -> Self {
+        self.bar_width = width;
+        self
+    }
+
+    /// Set orientation of the element as vertical. Argument axis is X.
+    pub fn vertical(mut self) -> Self {
+        self.orientation = Orientation::Vertical;
+        self
+    }
+
+    /// Set orientation of the element as horizontal. Argument axis is Y.
+    pub fn horizontal(mut self) -> Self {
+        self.orientation = Orientation::Horizontal;
+        self
+    }
+
+    pub(super) fn lower(&self) -> f64 {
+        if self.value.is_sign_positive() {
+            self.base_offset.unwrap_or(0.0)
+        } else {
+            self.base_offset.map_or(self.value, |o| o + self.value)
+        }
+    }
+
+    pub(super) fn upper(&self) -> f64 {
+        if self.value.is_sign_positive() {
+            self.base_offset.map_or(self.value, |o| o + self.value)
+        } else {
+            self.base_offset.unwrap_or(0.0)
+        }
+    }
+
+    pub(super) fn add_shapes(
+        &self,
+        transform: &ScreenTransform,
+        highlighted: bool,
+        shapes: &mut Vec<Shape>,
+    ) {
+        let (stroke, fill) = if highlighted {
+            highlighted_color(self.stroke, self.fill)
+        } else {
+            (self.stroke, self.fill)
+        };
+
+        let rect = transform.rect_from_values(&self.bounds_min(), &self.bounds_max());
+        let rect = Shape::Rect(RectShape {
+            rect,
+            corner_radius: 0.0,
+            fill,
+            stroke,
+        });
+
+        shapes.push(rect);
+    }
+
+    pub(super) fn add_rulers_and_text(
+        &self,
+        parent: &BarChart,
+        plot: &PlotConfig<'_>,
+        shapes: &mut Vec<Shape>,
+    ) {
+        let text: Option<String> = parent
+            .element_formatter
+            .as_ref()
+            .map(|fmt| fmt(self, parent));
+
+        add_rulers_and_text(self, plot, text, shapes);
+    }
+}
+
+impl RectElement for Bar {
+    fn name(&self) -> &str {
+        self.name.as_str()
+    }
+
+    fn bounds_min(&self) -> Value {
+        self.point_at(self.argument - self.bar_width / 2.0, self.lower())
+    }
+
+    fn bounds_max(&self) -> Value {
+        self.point_at(self.argument + self.bar_width / 2.0, self.upper())
+    }
+
+    fn values_with_ruler(&self) -> Vec<Value> {
+        let base = self.base_offset.unwrap_or(0.0);
+        let value_center = self.point_at(self.argument, base + self.value);
+
+        let mut ruler_positions = vec![value_center];
+
+        if let Some(offset) = self.base_offset {
+            ruler_positions.push(self.point_at(self.argument, offset));
+        }
+
+        ruler_positions
+    }
+
+    fn orientation(&self) -> Orientation {
+        self.orientation
+    }
+
+    fn default_values_format(&self, transform: &ScreenTransform) -> String {
+        let scale = transform.dvalue_dpos();
+        let y_decimals = ((-scale[1].abs().log10()).ceil().at_least(0.0) as usize).at_most(6);
+        format!("\n{:.*}", y_decimals, self.value)
+    }
+}