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)
+    }
+}

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

@@ -0,0 +1,286 @@
+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::{BoxPlot, ScreenTransform, Value};
+
+/// Contains the values of a single box in a box plot.
+#[derive(Clone, Debug, PartialEq)]
+pub struct BoxSpread {
+    /// Value of lower whisker (typically minimum).
+    ///
+    /// The whisker is not drawn if `lower_whisker >= quartile1`.
+    pub lower_whisker: f64,
+
+    /// Value of lower box threshold (typically 25% quartile)
+    pub quartile1: f64,
+
+    /// Value of middle line in box (typically median)
+    pub median: f64,
+
+    /// Value of upper box threshold (typically 75% quartile)
+    pub quartile3: f64,
+
+    /// Value of upper whisker (typically maximum)
+    ///
+    /// The whisker is not drawn if `upper_whisker <= quartile3`.
+    pub upper_whisker: f64,
+}
+
+impl BoxSpread {
+    pub fn new(
+        lower_whisker: f64,
+        quartile1: f64,
+        median: f64,
+        quartile3: f64,
+        upper_whisker: f64,
+    ) -> Self {
+        Self {
+            lower_whisker,
+            quartile1,
+            median,
+            quartile3,
+            upper_whisker,
+        }
+    }
+}
+
+/// A box in a [`BoxPlot`] diagram. This is a low level graphical element; it will not compute quartiles and whiskers,
+/// letting one use their preferred formula. Use [`Points`][`super::Points`] to draw the outliers.
+#[derive(Clone, Debug, PartialEq)]
+pub struct BoxElem {
+    /// Name of plot element in the diagram (annotated by default formatter).
+    pub name: String,
+
+    /// Which direction the box faces in the diagram.
+    pub orientation: Orientation,
+
+    /// Position on the argument (input) axis -- X if vertical, Y if horizontal.
+    pub argument: f64,
+
+    /// Values of the box
+    pub spread: BoxSpread,
+
+    /// Thickness of the box
+    pub box_width: f64,
+
+    /// Width of the whisker at minimum/maximum
+    pub whisker_width: f64,
+
+    /// Line width and color
+    pub stroke: Stroke,
+
+    /// Fill color
+    pub fill: Color32,
+}
+
+impl BoxElem {
+    /// Create a box element. Its `orientation` is set by its [`BoxPlot`] parent.
+    ///
+    /// Check [`BoxElem`] fields for detailed description.
+    pub fn new(argument: f64, spread: BoxSpread) -> Self {
+        Self {
+            argument,
+            orientation: Orientation::default(),
+            name: String::default(),
+            spread,
+            box_width: 0.25,
+            whisker_width: 0.15,
+            stroke: Stroke::new(1.0, Color32::TRANSPARENT),
+            fill: Color32::TRANSPARENT,
+        }
+    }
+
+    /// Name of this box 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
+    }
+
+    /// Set the box width.
+    pub fn box_width(mut self, width: f64) -> Self {
+        self.box_width = width;
+        self
+    }
+
+    /// Set the whisker width.
+    pub fn whisker_width(mut self, width: f64) -> Self {
+        self.whisker_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 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.point_at(self.argument - self.box_width / 2.0, self.spread.quartile1),
+            &self.point_at(self.argument + self.box_width / 2.0, self.spread.quartile3),
+        );
+        let rect = Shape::Rect(RectShape {
+            rect,
+            corner_radius: 0.0,
+            fill,
+            stroke,
+        });
+        shapes.push(rect);
+
+        let line_between = |v1, v2| {
+            Shape::line_segment(
+                [
+                    transform.position_from_value(&v1),
+                    transform.position_from_value(&v2),
+                ],
+                stroke,
+            )
+        };
+        let median = line_between(
+            self.point_at(self.argument - self.box_width / 2.0, self.spread.median),
+            self.point_at(self.argument + self.box_width / 2.0, self.spread.median),
+        );
+        shapes.push(median);
+
+        if self.spread.upper_whisker > self.spread.quartile3 {
+            let high_whisker = line_between(
+                self.point_at(self.argument, self.spread.quartile3),
+                self.point_at(self.argument, self.spread.upper_whisker),
+            );
+            shapes.push(high_whisker);
+            if self.box_width > 0.0 {
+                let high_whisker_end = line_between(
+                    self.point_at(
+                        self.argument - self.whisker_width / 2.0,
+                        self.spread.upper_whisker,
+                    ),
+                    self.point_at(
+                        self.argument + self.whisker_width / 2.0,
+                        self.spread.upper_whisker,
+                    ),
+                );
+                shapes.push(high_whisker_end);
+            }
+        }
+
+        if self.spread.lower_whisker < self.spread.quartile1 {
+            let low_whisker = line_between(
+                self.point_at(self.argument, self.spread.quartile1),
+                self.point_at(self.argument, self.spread.lower_whisker),
+            );
+            shapes.push(low_whisker);
+            if self.box_width > 0.0 {
+                let low_whisker_end = line_between(
+                    self.point_at(
+                        self.argument - self.whisker_width / 2.0,
+                        self.spread.lower_whisker,
+                    ),
+                    self.point_at(
+                        self.argument + self.whisker_width / 2.0,
+                        self.spread.lower_whisker,
+                    ),
+                );
+                shapes.push(low_whisker_end);
+            }
+        }
+    }
+
+    pub(super) fn add_rulers_and_text(
+        &self,
+        parent: &BoxPlot,
+        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 BoxElem {
+    fn name(&self) -> &str {
+        self.name.as_str()
+    }
+
+    fn bounds_min(&self) -> Value {
+        let argument = self.argument - self.box_width.max(self.whisker_width) / 2.0;
+        let value = self.spread.lower_whisker;
+        self.point_at(argument, value)
+    }
+
+    fn bounds_max(&self) -> Value {
+        let argument = self.argument + self.box_width.max(self.whisker_width) / 2.0;
+        let value = self.spread.upper_whisker;
+        self.point_at(argument, value)
+    }
+
+    fn values_with_ruler(&self) -> Vec<Value> {
+        let median = self.point_at(self.argument, self.spread.median);
+        let q1 = self.point_at(self.argument, self.spread.quartile1);
+        let q3 = self.point_at(self.argument, self.spread.quartile3);
+        let upper = self.point_at(self.argument, self.spread.upper_whisker);
+        let lower = self.point_at(self.argument, self.spread.lower_whisker);
+
+        vec![median, q1, q3, upper, lower]
+    }
+
+    fn orientation(&self) -> Orientation {
+        self.orientation
+    }
+
+    fn corner_value(&self) -> Value {
+        self.point_at(self.argument, self.spread.upper_whisker)
+    }
+
+    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!(
+            "\nMax = {max:.decimals$}\
+             \nQuartile 3 = {q3:.decimals$}\
+             \nMedian = {med:.decimals$}\
+             \nQuartile 1 = {q1:.decimals$}\
+             \nMin = {min:.decimals$}",
+            max = self.spread.upper_whisker,
+            q3 = self.spread.quartile3,
+            med = self.spread.median,
+            q1 = self.spread.quartile1,
+            min = self.spread.lower_whisker,
+            decimals = y_decimals
+        )
+    }
+}

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

@@ -1,131 +1,89 @@
 //! Contains items that can be added to a plot.
 
-use std::ops::{Bound, RangeBounds, RangeInclusive};
+use std::ops::RangeInclusive;
 
 use epaint::Mesh;
 
-use super::transform::{PlotBounds, ScreenTransform};
+use crate::util::float_ord::FloatOrd;
 use crate::*;
 
+use super::{PlotBounds, ScreenTransform};
+use rect_elem::*;
+use values::*;
+
+pub use bar::Bar;
+pub use box_elem::{BoxElem, BoxSpread};
+pub use values::{LineStyle, MarkerShape, Value, Values};
+
+mod bar;
+mod box_elem;
+mod rect_elem;
+mod values;
+
 const DEFAULT_FILL_ALPHA: f32 = 0.05;
 
-/// A value in the value-space of the plot.
-///
-/// Uses f64 for improved accuracy to enable plotting
-/// large values (e.g. unix time on x axis).
-#[derive(Clone, Copy, Debug, PartialEq)]
-pub struct Value {
-    /// This is often something monotonically increasing, such as time, but doesn't have to be.
-    /// Goes from left to right.
-    pub x: f64,
-    /// Goes from bottom to top (inverse of everything else in egui!).
-    pub y: f64,
+/// Container to pass-through several parameters related to plot visualization
+pub(super) struct PlotConfig<'a> {
+    pub ui: &'a Ui,
+    pub transform: &'a ScreenTransform,
+    pub show_x: bool,
+    pub show_y: bool,
 }
 
-impl Value {
-    #[inline(always)]
-    pub fn new(x: impl Into<f64>, y: impl Into<f64>) -> Self {
-        Self {
-            x: x.into(),
-            y: y.into(),
+/// Trait shared by things that can be drawn in the plot.
+pub(super) trait PlotItem {
+    fn get_shapes(&self, ui: &mut Ui, transform: &ScreenTransform, shapes: &mut Vec<Shape>);
+    fn initialize(&mut self, x_range: RangeInclusive<f64>);
+    fn name(&self) -> &str;
+    fn color(&self) -> Color32;
+    fn highlight(&mut self);
+    fn highlighted(&self) -> bool;
+    fn geometry(&self) -> PlotGeometry<'_>;
+    fn get_bounds(&self) -> PlotBounds;
+
+    fn find_closest(&self, point: Pos2, transform: &ScreenTransform) -> Option<ClosestElem> {
+        match self.geometry() {
+            PlotGeometry::None => None,
+
+            PlotGeometry::Points(points) => points
+                .iter()
+                .enumerate()
+                .map(|(index, value)| {
+                    let pos = transform.position_from_value(value);
+                    let dist_sq = point.distance_sq(pos);
+                    ClosestElem { index, dist_sq }
+                })
+                .min_by_key(|e| e.dist_sq.ord()),
+
+            PlotGeometry::Rects => {
+                panic!("If the PlotItem is made of rects, it should implement find_closest()")
+            }
         }
     }
 
-    #[inline(always)]
-    pub fn to_pos2(self) -> Pos2 {
-        Pos2::new(self.x as f32, self.y as f32)
+    fn on_hover(&self, elem: ClosestElem, shapes: &mut Vec<Shape>, plot: &PlotConfig<'_>) {
+        let points = match self.geometry() {
+            PlotGeometry::Points(points) => points,
+            PlotGeometry::None => {
+                panic!("If the PlotItem has no geometry, on_hover() must not be called")
             }
+            PlotGeometry::Rects => {
+                panic!("If the PlotItem is made of rects, it should implement on_hover()")
+            }
+        };
 
-    #[inline(always)]
-    pub fn to_vec2(self) -> Vec2 {
-        Vec2::new(self.x as f32, self.y as f32)
-    }
-}
+        let line_color = if plot.ui.visuals().dark_mode {
+            Color32::from_gray(100).additive()
+        } else {
+            Color32::from_black_alpha(180)
+        };
 
-// ----------------------------------------------------------------------------
+        // this method is only called, if the value is in the result set of find_closest()
+        let value = points[elem.index];
+        let pointer = plot.transform.position_from_value(&value);
+        shapes.push(Shape::circle_filled(pointer, 3.0, line_color));
 
-#[derive(Debug, PartialEq, Clone, Copy)]
-pub enum LineStyle {
-    Solid,
-    Dotted { spacing: f32 },
-    Dashed { length: f32 },
-}
-
-impl LineStyle {
-    pub fn dashed_loose() -> Self {
-        Self::Dashed { length: 10.0 }
-    }
-
-    pub fn dashed_dense() -> Self {
-        Self::Dashed { length: 5.0 }
-    }
-
-    pub fn dotted_loose() -> Self {
-        Self::Dotted { spacing: 10.0 }
-    }
-
-    pub fn dotted_dense() -> Self {
-        Self::Dotted { spacing: 5.0 }
-    }
-
-    fn style_line(
-        &self,
-        line: Vec<Pos2>,
-        mut stroke: Stroke,
-        highlight: bool,
-        shapes: &mut Vec<Shape>,
-    ) {
-        match line.len() {
-            0 => {}
-            1 => {
-                let mut radius = stroke.width / 2.0;
-                if highlight {
-                    radius *= 2f32.sqrt();
-                }
-                shapes.push(Shape::circle_filled(line[0], radius, stroke.color));
-            }
-            _ => {
-                match self {
-                    LineStyle::Solid => {
-                        if highlight {
-                            stroke.width *= 2.0;
-                        }
-                        shapes.push(Shape::line(line, stroke));
-                    }
-                    LineStyle::Dotted { spacing } => {
-                        // Take the stroke width for the radius even though it's not "correct", otherwise
-                        // the dots would become too small.
-                        let mut radius = stroke.width;
-                        if highlight {
-                            radius *= 2f32.sqrt();
-                        }
-                        shapes.extend(Shape::dotted_line(&line, stroke.color, *spacing, radius));
-                    }
-                    LineStyle::Dashed { length } => {
-                        if highlight {
-                            stroke.width *= 2.0;
-                        }
-                        let golden_ratio = (5.0_f32.sqrt() - 1.0) / 2.0; // 0.61803398875
-                        shapes.extend(Shape::dashed_line(
-                            &line,
-                            stroke,
-                            *length,
-                            length * golden_ratio,
-                        ));
-                    }
-                }
-            }
-        }
-    }
-}
-
-impl ToString for LineStyle {
-    fn to_string(&self) -> String {
-        match self {
-            LineStyle::Solid => "Solid".into(),
-            LineStyle::Dotted { spacing } => format!("Dotted{}Px", spacing),
-            LineStyle::Dashed { length } => format!("Dashed{}Px", length),
-        }
+        rulers_at_value(pointer, value, self.name(), plot, shapes);
     }
 }
 
@@ -229,8 +187,8 @@ impl PlotItem for HLine {
         self.highlight
     }
 
-    fn values(&self) -> Option<&Values> {
-        None
+    fn geometry(&self) -> PlotGeometry<'_> {
+        PlotGeometry::None
     }
 
     fn get_bounds(&self) -> PlotBounds {
@@ -339,8 +297,8 @@ impl PlotItem for VLine {
         self.highlight
     }
 
-    fn values(&self) -> Option<&Values> {
-        None
+    fn geometry(&self) -> PlotGeometry<'_> {
+        PlotGeometry::None
     }
 
     fn get_bounds(&self) -> PlotBounds {
@@ -351,203 +309,6 @@ impl PlotItem for VLine {
     }
 }
 
-/// Trait shared by things that can be drawn in the plot.
-pub(super) trait PlotItem {
-    fn get_shapes(&self, ui: &mut Ui, transform: &ScreenTransform, shapes: &mut Vec<Shape>);
-    fn initialize(&mut self, x_range: RangeInclusive<f64>);
-    fn name(&self) -> &str;
-    fn color(&self) -> Color32;
-    fn highlight(&mut self);
-    fn highlighted(&self) -> bool;
-    fn values(&self) -> Option<&Values>;
-    fn get_bounds(&self) -> PlotBounds;
-}
-
-// ----------------------------------------------------------------------------
-
-/// Describes a function y = f(x) with an optional range for x and a number of points.
-struct ExplicitGenerator {
-    function: Box<dyn Fn(f64) -> f64>,
-    x_range: RangeInclusive<f64>,
-    points: usize,
-}
-
-pub struct Values {
-    pub(super) values: Vec<Value>,
-    generator: Option<ExplicitGenerator>,
-}
-
-impl Default for Values {
-    fn default() -> Self {
-        Self {
-            values: Vec::new(),
-            generator: None,
-        }
-    }
-}
-
-impl Values {
-    pub fn from_values(values: Vec<Value>) -> Self {
-        Self {
-            values,
-            generator: None,
-        }
-    }
-
-    pub fn from_values_iter(iter: impl Iterator<Item = Value>) -> Self {
-        Self::from_values(iter.collect())
-    }
-
-    /// Draw a line based on a function `y=f(x)`, a range (which can be infinite) for x and the number of points.
-    pub fn from_explicit_callback(
-        function: impl Fn(f64) -> f64 + 'static,
-        x_range: impl RangeBounds<f64>,
-        points: usize,
-    ) -> Self {
-        let start = match x_range.start_bound() {
-            Bound::Included(x) | Bound::Excluded(x) => *x,
-            Bound::Unbounded => f64::NEG_INFINITY,
-        };
-        let end = match x_range.end_bound() {
-            Bound::Included(x) | Bound::Excluded(x) => *x,
-            Bound::Unbounded => f64::INFINITY,
-        };
-        let x_range = start..=end;
-
-        let generator = ExplicitGenerator {
-            function: Box::new(function),
-            x_range,
-            points,
-        };
-
-        Self {
-            values: Vec::new(),
-            generator: Some(generator),
-        }
-    }
-
-    /// Draw a line based on a function `(x,y)=f(t)`, a range for t and the number of points.
-    /// The range may be specified as start..end or as start..=end.
-    pub fn from_parametric_callback(
-        function: impl Fn(f64) -> (f64, f64),
-        t_range: impl RangeBounds<f64>,
-        points: usize,
-    ) -> Self {
-        let start = match t_range.start_bound() {
-            Bound::Included(x) => x,
-            Bound::Excluded(_) => unreachable!(),
-            Bound::Unbounded => panic!("The range for parametric functions must be bounded!"),
-        };
-        let end = match t_range.end_bound() {
-            Bound::Included(x) | Bound::Excluded(x) => x,
-            Bound::Unbounded => panic!("The range for parametric functions must be bounded!"),
-        };
-        let last_point_included = matches!(t_range.end_bound(), Bound::Included(_));
-        let increment = if last_point_included {
-            (end - start) / (points - 1) as f64
-        } else {
-            (end - start) / points as f64
-        };
-        let values = (0..points).map(|i| {
-            let t = start + i as f64 * increment;
-            let (x, y) = function(t);
-            Value { x, y }
-        });
-        Self::from_values_iter(values)
-    }
-
-    /// From a series of y-values.
-    /// The x-values will be the indices of these values
-    pub fn from_ys_f32(ys: &[f32]) -> Self {
-        let values: Vec<Value> = ys
-            .iter()
-            .enumerate()
-            .map(|(i, &y)| Value {
-                x: i as f64,
-                y: y as f64,
-            })
-            .collect();
-        Self::from_values(values)
-    }
-
-    /// Returns true if there are no data points available and there is no function to generate any.
-    pub(super) fn is_empty(&self) -> bool {
-        self.generator.is_none() && self.values.is_empty()
-    }
-
-    /// If initialized with a generator function, this will generate `n` evenly spaced points in the
-    /// given range.
-    pub(super) fn generate_points(&mut self, x_range: RangeInclusive<f64>) {
-        if let Some(generator) = self.generator.take() {
-            if let Some(intersection) = Self::range_intersection(&x_range, &generator.x_range) {
-                let increment =
-                    (intersection.end() - intersection.start()) / (generator.points - 1) as f64;
-                self.values = (0..generator.points)
-                    .map(|i| {
-                        let x = intersection.start() + i as f64 * increment;
-                        let y = (generator.function)(x);
-                        Value { x, y }
-                    })
-                    .collect();
-            }
-        }
-    }
-
-    /// Returns the intersection of two ranges if they intersect.
-    fn range_intersection(
-        range1: &RangeInclusive<f64>,
-        range2: &RangeInclusive<f64>,
-    ) -> Option<RangeInclusive<f64>> {
-        let start = range1.start().max(*range2.start());
-        let end = range1.end().min(*range2.end());
-        (start < end).then(|| start..=end)
-    }
-
-    pub(super) fn get_bounds(&self) -> PlotBounds {
-        let mut bounds = PlotBounds::NOTHING;
-        self.values
-            .iter()
-            .for_each(|value| bounds.extend_with(value));
-        bounds
-    }
-}
-
-// ----------------------------------------------------------------------------
-
-#[derive(Debug, PartialEq, Eq, Clone, Copy)]
-pub enum MarkerShape {
-    Circle,
-    Diamond,
-    Square,
-    Cross,
-    Plus,
-    Up,
-    Down,
-    Left,
-    Right,
-    Asterisk,
-}
-
-impl MarkerShape {
-    /// Get a vector containing all marker shapes.
-    pub fn all() -> impl Iterator<Item = MarkerShape> {
-        [
-            Self::Circle,
-            Self::Diamond,
-            Self::Square,
-            Self::Cross,
-            Self::Plus,
-            Self::Up,
-            Self::Down,
-            Self::Left,
-            Self::Right,
-            Self::Asterisk,
-        ]
-        .iter()
-        .copied()
-    }
-}
-
 /// A series of values forming a path.
 pub struct Line {
     pub(super) series: Values,
@@ -706,8 +467,8 @@ impl PlotItem for Line {
         self.highlight
     }
 
-    fn values(&self) -> Option<&Values> {
-        Some(&self.series)
+    fn geometry(&self) -> PlotGeometry<'_> {
+        PlotGeometry::Points(&self.series.values)
     }
 
     fn get_bounds(&self) -> PlotBounds {
@@ -836,8 +597,8 @@ impl PlotItem for Polygon {
         self.highlight
     }
 
-    fn values(&self) -> Option<&Values> {
-        Some(&self.series)
+    fn geometry(&self) -> PlotGeometry<'_> {
+        PlotGeometry::Points(&self.series.values)
     }
 
     fn get_bounds(&self) -> PlotBounds {
@@ -949,8 +710,8 @@ impl PlotItem for Text {
         self.highlight
     }
 
-    fn values(&self) -> Option<&Values> {
-        None
+    fn geometry(&self) -> PlotGeometry<'_> {
+        PlotGeometry::None
     }
 
     fn get_bounds(&self) -> PlotBounds {
@@ -1182,8 +943,8 @@ impl PlotItem for Points {
         self.highlight
     }
 
-    fn values(&self) -> Option<&Values> {
-        Some(&self.series)
+    fn geometry(&self) -> PlotGeometry<'_> {
+        PlotGeometry::Points(&self.series.values)
     }
 
     fn get_bounds(&self) -> PlotBounds {
@@ -1297,8 +1058,8 @@ impl PlotItem for Arrows {
         self.highlight
     }
 
-    fn values(&self) -> Option<&Values> {
-        Some(&self.origins)
+    fn geometry(&self) -> PlotGeometry<'_> {
+        PlotGeometry::Points(&self.origins.values)
     }
 
     fn get_bounds(&self) -> PlotBounds {
@@ -1427,8 +1188,8 @@ impl PlotItem for PlotImage {
         self.highlight
     }
 
-    fn values(&self) -> Option<&Values> {
-        None
+    fn geometry(&self) -> PlotGeometry<'_> {
+        PlotGeometry::None
     }
 
     fn get_bounds(&self) -> PlotBounds {
@@ -1446,3 +1207,477 @@ impl PlotItem for PlotImage {
         bounds
     }
 }
+
+// ----------------------------------------------------------------------------
+
+/// A bar chart.
+pub struct BarChart {
+    pub(super) bars: Vec<Bar>,
+    pub(super) default_color: Color32,
+    pub(super) name: String,
+    /// A custom element formatter
+    pub(super) element_formatter: Option<Box<dyn Fn(&Bar, &BarChart) -> String>>,
+    highlight: bool,
+}
+
+impl BarChart {
+    /// Create a bar chart. It defaults to vertically oriented elements.
+    pub fn new(bars: Vec<Bar>) -> BarChart {
+        BarChart {
+            bars,
+            default_color: Color32::TRANSPARENT,
+            name: String::new(),
+            element_formatter: None,
+            highlight: false,
+        }
+    }
+
+    /// Set the default color. It is set on all elements that do not already have a specific color.
+    /// This is the color that shows up in the legend.
+    /// It can be overridden at the bar level (see [[`Bar`]]).
+    /// Default is `Color32::TRANSPARENT` which means a color will be auto-assigned.
+    pub fn color(mut self, color: impl Into<Color32>) -> Self {
+        let plot_color = color.into();
+        self.default_color = plot_color;
+        self.bars.iter_mut().for_each(|b| {
+            if b.fill == Color32::TRANSPARENT && b.stroke.color == Color32::TRANSPARENT {
+                b.fill = plot_color.linear_multiply(0.2);
+                b.stroke.color = plot_color;
+            }
+        });
+        self
+    }
+
+    /// Name of this chart.
+    ///
+    /// This name will show up in the plot legend, if legends are turned on. Multiple charts may
+    /// share the same name, in which case they will also share an entry in the legend.
+    #[allow(clippy::needless_pass_by_value)]
+    pub fn name(mut self, name: impl ToString) -> Self {
+        self.name = name.to_string();
+        self
+    }
+
+    /// Set all elements to be in a vertical orientation.
+    /// Argument axis will be X and bar values will be on the Y axis.
+    pub fn vertical(mut self) -> Self {
+        self.bars.iter_mut().for_each(|b| {
+            b.orientation = Orientation::Vertical;
+        });
+        self
+    }
+
+    /// Set all elements to be in a horizontal orientation.
+    /// Argument axis will be Y and bar values will be on the X axis.
+    pub fn horizontal(mut self) -> Self {
+        self.bars.iter_mut().for_each(|b| {
+            b.orientation = Orientation::Horizontal;
+        });
+        self
+    }
+
+    /// Set the width (thickness) of all its elements.
+    pub fn width(mut self, width: f64) -> Self {
+        self.bars.iter_mut().for_each(|b| {
+            b.bar_width = width;
+        });
+        self
+    }
+
+    /// Highlight all plot elements.
+    pub fn highlight(mut self) -> Self {
+        self.highlight = true;
+        self
+    }
+
+    /// Add a custom way to format an element.
+    /// Can be used to display a set number of decimals or custom labels.
+    pub fn element_formatter(mut self, formatter: Box<dyn Fn(&Bar, &BarChart) -> String>) -> Self {
+        self.element_formatter = Some(formatter);
+        self
+    }
+
+    /// Stacks the bars on top of another chart.
+    /// Positive values are stacked on top of other positive values.
+    /// Negative values are stacked below other negative values.
+    pub fn stack_on(mut self, others: &[&BarChart]) -> Self {
+        for (index, bar) in self.bars.iter_mut().enumerate() {
+            let new_base_offset = if bar.value.is_sign_positive() {
+                others
+                    .iter()
+                    .filter_map(|other_chart| other_chart.bars.get(index).map(|bar| bar.upper()))
+                    .max_by_key(|value| value.ord())
+            } else {
+                others
+                    .iter()
+                    .filter_map(|other_chart| other_chart.bars.get(index).map(|bar| bar.lower()))
+                    .min_by_key(|value| value.ord())
+            };
+
+            if let Some(value) = new_base_offset {
+                bar.base_offset = Some(value);
+            }
+        }
+        self
+    }
+}
+
+impl PlotItem for BarChart {
+    fn get_shapes(&self, _ui: &mut Ui, transform: &ScreenTransform, shapes: &mut Vec<Shape>) {
+        self.bars.iter().for_each(|b| {
+            b.add_shapes(transform, self.highlight, shapes);
+        });
+    }
+
+    fn initialize(&mut self, _x_range: RangeInclusive<f64>) {
+        // nothing to do
+    }
+
+    fn name(&self) -> &str {
+        self.name.as_str()
+    }
+
+    fn color(&self) -> Color32 {
+        self.default_color
+    }
+
+    fn highlight(&mut self) {
+        self.highlight = true;
+    }
+
+    fn highlighted(&self) -> bool {
+        self.highlight
+    }
+
+    fn geometry(&self) -> PlotGeometry<'_> {
+        PlotGeometry::Rects
+    }
+
+    fn get_bounds(&self) -> PlotBounds {
+        let mut bounds = PlotBounds::NOTHING;
+        self.bars.iter().for_each(|b| {
+            bounds.merge(&b.bounds());
+        });
+        bounds
+    }
+
+    fn find_closest(&self, point: Pos2, transform: &ScreenTransform) -> Option<ClosestElem> {
+        find_closest_rect(&self.bars, point, transform)
+    }
+
+    fn on_hover(&self, elem: ClosestElem, shapes: &mut Vec<Shape>, plot: &PlotConfig<'_>) {
+        let bar = &self.bars[elem.index];
+
+        bar.add_shapes(plot.transform, true, shapes);
+        bar.add_rulers_and_text(self, plot, shapes);
+    }
+}
+
+/// A diagram containing a series of [`BoxElem`] elements.
+pub struct BoxPlot {
+    pub(super) boxes: Vec<BoxElem>,
+    pub(super) default_color: Color32,
+    pub(super) name: String,
+    /// A custom element formatter
+    pub(super) element_formatter: Option<Box<dyn Fn(&BoxElem, &BoxPlot) -> String>>,
+    highlight: bool,
+}
+
+impl BoxPlot {
+    /// Create a plot containing multiple `boxes`. It defaults to vertically oriented elements.
+    pub fn new(boxes: Vec<BoxElem>) -> Self {
+        Self {
+            boxes,
+            default_color: Color32::TRANSPARENT,
+            name: String::new(),
+            element_formatter: None,
+            highlight: false,
+        }
+    }
+
+    /// Set the default color. It is set on all elements that do not already have a specific color.
+    /// This is the color that shows up in the legend.
+    /// It can be overridden at the element level (see [`BoxElem`]).
+    /// Default is `Color32::TRANSPARENT` which means a color will be auto-assigned.
+    pub fn color(mut self, color: impl Into<Color32>) -> Self {
+        let plot_color = color.into();
+        self.default_color = plot_color;
+        self.boxes.iter_mut().for_each(|box_elem| {
+            if box_elem.fill == Color32::TRANSPARENT
+                && box_elem.stroke.color == Color32::TRANSPARENT
+            {
+                box_elem.fill = plot_color.linear_multiply(0.2);
+                box_elem.stroke.color = plot_color;
+            }
+        });
+        self
+    }
+
+    /// Name of this box plot diagram.
+    ///
+    /// This name will show up in the plot legend, if legends are turned on. Multiple series may
+    /// share the same name, in which case they will also share an entry in the legend.
+    #[allow(clippy::needless_pass_by_value)]
+    pub fn name(mut self, name: impl ToString) -> Self {
+        self.name = name.to_string();
+        self
+    }
+
+    /// Set all elements to be in a vertical orientation.
+    /// Argument axis will be X and values will be on the Y axis.
+    pub fn vertical(mut self) -> Self {
+        self.boxes.iter_mut().for_each(|box_elem| {
+            box_elem.orientation = Orientation::Vertical;
+        });
+        self
+    }
+
+    /// Set all elements to be in a horizontal orientation.
+    /// Argument axis will be Y and values will be on the X axis.
+    pub fn horizontal(mut self) -> Self {
+        self.boxes.iter_mut().for_each(|box_elem| {
+            box_elem.orientation = Orientation::Horizontal;
+        });
+        self
+    }
+
+    /// Highlight all plot elements.
+    pub fn highlight(mut self) -> Self {
+        self.highlight = true;
+        self
+    }
+
+    /// Add a custom way to format an element.
+    /// Can be used to display a set number of decimals or custom labels.
+    pub fn element_formatter(
+        mut self,
+        formatter: Box<dyn Fn(&BoxElem, &BoxPlot) -> String>,
+    ) -> Self {
+        self.element_formatter = Some(formatter);
+        self
+    }
+}
+
+impl PlotItem for BoxPlot {
+    fn get_shapes(&self, _ui: &mut Ui, transform: &ScreenTransform, shapes: &mut Vec<Shape>) {
+        self.boxes.iter().for_each(|b| {
+            b.add_shapes(transform, self.highlight, shapes);
+        });
+    }
+
+    fn initialize(&mut self, _x_range: RangeInclusive<f64>) {
+        // nothing to do
+    }
+
+    fn name(&self) -> &str {
+        self.name.as_str()
+    }
+
+    fn color(&self) -> Color32 {
+        self.default_color
+    }
+
+    fn highlight(&mut self) {
+        self.highlight = true;
+    }
+
+    fn highlighted(&self) -> bool {
+        self.highlight
+    }
+
+    fn geometry(&self) -> PlotGeometry<'_> {
+        PlotGeometry::Rects
+    }
+
+    fn get_bounds(&self) -> PlotBounds {
+        let mut bounds = PlotBounds::NOTHING;
+        self.boxes.iter().for_each(|b| {
+            bounds.merge(&b.bounds());
+        });
+        bounds
+    }
+
+    fn find_closest(&self, point: Pos2, transform: &ScreenTransform) -> Option<ClosestElem> {
+        find_closest_rect(&self.boxes, point, transform)
+    }
+
+    fn on_hover(&self, elem: ClosestElem, shapes: &mut Vec<Shape>, plot: &PlotConfig<'_>) {
+        let box_plot = &self.boxes[elem.index];
+
+        box_plot.add_shapes(plot.transform, true, shapes);
+        box_plot.add_rulers_and_text(self, plot, shapes);
+    }
+}
+
+// ----------------------------------------------------------------------------
+// Helper functions
+
+fn rulers_color(ui: &Ui) -> Color32 {
+    if ui.visuals().dark_mode {
+        Color32::from_gray(100).additive()
+    } else {
+        Color32::from_black_alpha(180)
+    }
+}
+
+fn vertical_line(pointer: Pos2, transform: &ScreenTransform, line_color: Color32) -> Shape {
+    let frame = transform.frame();
+    Shape::line_segment(
+        [
+            pos2(pointer.x, frame.top()),
+            pos2(pointer.x, frame.bottom()),
+        ],
+        (1.0, line_color),
+    )
+}
+
+fn horizontal_line(pointer: Pos2, transform: &ScreenTransform, line_color: Color32) -> Shape {
+    let frame = transform.frame();
+    Shape::line_segment(
+        [
+            pos2(frame.left(), pointer.y),
+            pos2(frame.right(), pointer.y),
+        ],
+        (1.0, line_color),
+    )
+}
+
+fn add_rulers_and_text(
+    elem: &dyn RectElement,
+    plot: &PlotConfig<'_>,
+    text: Option<String>,
+    shapes: &mut Vec<Shape>,
+) {
+    let orientation = elem.orientation();
+    let show_argument = plot.show_x && orientation == Orientation::Vertical
+        || plot.show_y && orientation == Orientation::Horizontal;
+    let show_values = plot.show_y && orientation == Orientation::Vertical
+        || plot.show_x && orientation == Orientation::Horizontal;
+
+    let line_color = rulers_color(plot.ui);
+
+    // Rulers for argument (usually vertical)
+    if show_argument {
+        let push_argument_ruler = |argument: Value, shapes: &mut Vec<Shape>| {
+            let position = plot.transform.position_from_value(&argument);
+            let line = match orientation {
+                Orientation::Horizontal => horizontal_line(position, plot.transform, line_color),
+                Orientation::Vertical => vertical_line(position, plot.transform, line_color),
+            };
+            shapes.push(line);
+        };
+
+        for pos in elem.arguments_with_ruler() {
+            push_argument_ruler(pos, shapes);
+        }
+    }
+
+    // Rulers for values (usually horizontal)
+    if show_values {
+        let push_value_ruler = |value: Value, shapes: &mut Vec<Shape>| {
+            let position = plot.transform.position_from_value(&value);
+            let line = match orientation {
+                Orientation::Horizontal => vertical_line(position, plot.transform, line_color),
+                Orientation::Vertical => horizontal_line(position, plot.transform, line_color),
+            };
+            shapes.push(line);
+        };
+
+        for pos in elem.values_with_ruler() {
+            push_value_ruler(pos, shapes);
+        }
+    }
+
+    // Text
+    let text = text.unwrap_or({
+        let mut text = elem.name().to_string(); // could be empty
+
+        if show_values {
+            text.push_str(&elem.default_values_format(plot.transform));
+        }
+
+        text
+    });
+
+    let corner_value = elem.corner_value();
+    shapes.push(Shape::text(
+        plot.ui.fonts(),
+        plot.transform.position_from_value(&corner_value) + vec2(3.0, -2.0),
+        Align2::LEFT_BOTTOM,
+        text,
+        TextStyle::Body,
+        plot.ui.visuals().text_color(),
+    ));
+}
+
+/// Draws a cross of horizontal and vertical ruler at the `pointer` position.
+/// `value` is used to for text displaying X/Y coordinates.
+#[allow(clippy::too_many_arguments)]
+pub(super) fn rulers_at_value(
+    pointer: Pos2,
+    value: Value,
+    name: &str,
+    plot: &PlotConfig<'_>,
+    shapes: &mut Vec<Shape>,
+) {
+    let line_color = rulers_color(plot.ui);
+    if plot.show_x {
+        shapes.push(vertical_line(pointer, plot.transform, line_color));
+    }
+    if plot.show_y {
+        shapes.push(horizontal_line(pointer, plot.transform, line_color));
+    }
+
+    let mut prefix = String::new();
+
+    if !name.is_empty() {
+        prefix = format!("{}\n", name);
+    }
+
+    let text = {
+        let scale = plot.transform.dvalue_dpos();
+        let x_decimals = ((-scale[0].abs().log10()).ceil().at_least(0.0) as usize).at_most(6);
+        let y_decimals = ((-scale[1].abs().log10()).ceil().at_least(0.0) as usize).at_most(6);
+        if plot.show_x && plot.show_y {
+            format!(
+                "{}x = {:.*}\ny = {:.*}",
+                prefix, x_decimals, value.x, y_decimals, value.y
+            )
+        } else if plot.show_x {
+            format!("{}x = {:.*}", prefix, x_decimals, value.x)
+        } else if plot.show_y {
+            format!("{}y = {:.*}", prefix, y_decimals, value.y)
+        } else {
+            unreachable!()
+        }
+    };
+
+    shapes.push(Shape::text(
+        plot.ui.fonts(),
+        pointer + vec2(3.0, -2.0),
+        Align2::LEFT_BOTTOM,
+        text,
+        TextStyle::Body,
+        plot.ui.visuals().text_color(),
+    ));
+}
+
+fn find_closest_rect<'a, T>(
+    rects: impl IntoIterator<Item = &'a T>,
+    point: Pos2,
+    transform: &ScreenTransform,
+) -> Option<ClosestElem>
+where
+    T: 'a + RectElement,
+{
+    rects
+        .into_iter()
+        .enumerate()
+        .map(|(index, bar)| {
+            let bar_rect: Rect = transform.rect_from_values(&bar.bounds_min(), &bar.bounds_max());
+            let dist_sq = bar_rect.distance_sq_to_pos(point);
+
+            ClosestElem { index, dist_sq }
+        })
+        .min_by_key(|e| e.dist_sq.ord())
+}

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

@@ -0,0 +1,61 @@
+use super::{Orientation, Value};
+use crate::plot::transform::{PlotBounds, ScreenTransform};
+use epaint::emath::NumExt;
+use epaint::{Color32, Rgba, Stroke};
+
+/// Trait that abstracts from rectangular 'Value'-like elements, such as bars or boxes
+pub(super) trait RectElement {
+    fn name(&self) -> &str;
+    fn bounds_min(&self) -> Value;
+    fn bounds_max(&self) -> Value;
+
+    fn bounds(&self) -> PlotBounds {
+        let mut bounds = PlotBounds::NOTHING;
+        bounds.extend_with(&self.bounds_min());
+        bounds.extend_with(&self.bounds_max());
+        bounds
+    }
+
+    /// At which argument (input; usually X) there is a ruler (usually vertical)
+    fn arguments_with_ruler(&self) -> Vec<Value> {
+        // Default: one at center
+        vec![self.bounds().center()]
+    }
+
+    /// At which value (output; usually Y) there is a ruler (usually horizontal)
+    fn values_with_ruler(&self) -> Vec<Value>;
+
+    /// The diagram's orientation (vertical/horizontal)
+    fn orientation(&self) -> Orientation;
+
+    /// Get X/Y-value for (argument, value) pair, taking into account orientation
+    fn point_at(&self, argument: f64, value: f64) -> Value {
+        match self.orientation() {
+            Orientation::Horizontal => Value::new(value, argument),
+            Orientation::Vertical => Value::new(argument, value),
+        }
+    }
+
+    /// Right top of the rectangle (position of text)
+    fn corner_value(&self) -> Value {
+        //self.point_at(self.position + self.width / 2.0, value)
+        Value {
+            x: self.bounds_max().x,
+            y: self.bounds_max().y,
+        }
+    }
+
+    /// Debug formatting for hovered-over value, if none is specified by the user
+    fn default_values_format(&self, transform: &ScreenTransform) -> String;
+}
+
+// ----------------------------------------------------------------------------
+// Helper functions
+
+pub(super) fn highlighted_color(mut stroke: Stroke, fill: Color32) -> (Stroke, Color32) {
+    stroke.width *= 2.0;
+    let fill = Rgba::from(fill);
+    let fill_alpha = (2.0 * fill.a()).at_most(1.0);
+    let fill = fill.to_opaque().multiply(fill_alpha);
+    (stroke, fill.into())
+}

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

@@ -0,0 +1,352 @@
+use epaint::{Pos2, Shape, Stroke, Vec2};
+use std::ops::{Bound, RangeBounds, RangeInclusive};
+
+use crate::plot::transform::PlotBounds;
+
+/// A value in the value-space of the plot.
+///
+/// Uses f64 for improved accuracy to enable plotting
+/// large values (e.g. unix time on x axis).
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub struct Value {
+    /// This is often something monotonically increasing, such as time, but doesn't have to be.
+    /// Goes from left to right.
+    pub x: f64,
+    /// Goes from bottom to top (inverse of everything else in egui!).
+    pub y: f64,
+}
+
+impl Value {
+    #[inline(always)]
+    pub fn new(x: impl Into<f64>, y: impl Into<f64>) -> Self {
+        Self {
+            x: x.into(),
+            y: y.into(),
+        }
+    }
+
+    #[inline(always)]
+    pub fn to_pos2(self) -> Pos2 {
+        Pos2::new(self.x as f32, self.y as f32)
+    }
+
+    #[inline(always)]
+    pub fn to_vec2(self) -> Vec2 {
+        Vec2::new(self.x as f32, self.y as f32)
+    }
+}
+
+// ----------------------------------------------------------------------------
+
+#[derive(Debug, PartialEq, Clone, Copy)]
+pub enum LineStyle {
+    Solid,
+    Dotted { spacing: f32 },
+    Dashed { length: f32 },
+}
+
+impl LineStyle {
+    pub fn dashed_loose() -> Self {
+        Self::Dashed { length: 10.0 }
+    }
+
+    pub fn dashed_dense() -> Self {
+        Self::Dashed { length: 5.0 }
+    }
+
+    pub fn dotted_loose() -> Self {
+        Self::Dotted { spacing: 10.0 }
+    }
+
+    pub fn dotted_dense() -> Self {
+        Self::Dotted { spacing: 5.0 }
+    }
+
+    pub(super) fn style_line(
+        &self,
+        line: Vec<Pos2>,
+        mut stroke: Stroke,
+        highlight: bool,
+        shapes: &mut Vec<Shape>,
+    ) {
+        match line.len() {
+            0 => {}
+            1 => {
+                let mut radius = stroke.width / 2.0;
+                if highlight {
+                    radius *= 2f32.sqrt();
+                }
+                shapes.push(Shape::circle_filled(line[0], radius, stroke.color));
+            }
+            _ => {
+                match self {
+                    LineStyle::Solid => {
+                        if highlight {
+                            stroke.width *= 2.0;
+                        }
+                        shapes.push(Shape::line(line, stroke));
+                    }
+                    LineStyle::Dotted { spacing } => {
+                        // Take the stroke width for the radius even though it's not "correct", otherwise
+                        // the dots would become too small.
+                        let mut radius = stroke.width;
+                        if highlight {
+                            radius *= 2f32.sqrt();
+                        }
+                        shapes.extend(Shape::dotted_line(&line, stroke.color, *spacing, radius));
+                    }
+                    LineStyle::Dashed { length } => {
+                        if highlight {
+                            stroke.width *= 2.0;
+                        }
+                        let golden_ratio = (5.0_f32.sqrt() - 1.0) / 2.0; // 0.61803398875
+                        shapes.extend(Shape::dashed_line(
+                            &line,
+                            stroke,
+                            *length,
+                            length * golden_ratio,
+                        ));
+                    }
+                }
+            }
+        }
+    }
+}
+
+impl ToString for LineStyle {
+    fn to_string(&self) -> String {
+        match self {
+            LineStyle::Solid => "Solid".into(),
+            LineStyle::Dotted { spacing } => format!("Dotted{}Px", spacing),
+            LineStyle::Dashed { length } => format!("Dashed{}Px", length),
+        }
+    }
+}
+
+// ----------------------------------------------------------------------------
+
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+pub enum Orientation {
+    Horizontal,
+    Vertical,
+}
+
+impl Default for Orientation {
+    fn default() -> Self {
+        Self::Vertical
+    }
+}
+
+// ----------------------------------------------------------------------------
+
+pub struct Values {
+    pub(super) values: Vec<Value>,
+    generator: Option<ExplicitGenerator>,
+}
+
+impl Default for Values {
+    fn default() -> Self {
+        Self {
+            values: Vec::new(),
+            generator: None,
+        }
+    }
+}
+
+impl Values {
+    pub fn from_values(values: Vec<Value>) -> Self {
+        Self {
+            values,
+            generator: None,
+        }
+    }
+
+    pub fn from_values_iter(iter: impl Iterator<Item = Value>) -> Self {
+        Self::from_values(iter.collect())
+    }
+
+    /// Draw a line based on a function `y=f(x)`, a range (which can be infinite) for x and the number of points.
+    pub fn from_explicit_callback(
+        function: impl Fn(f64) -> f64 + 'static,
+        x_range: impl RangeBounds<f64>,
+        points: usize,
+    ) -> Self {
+        let start = match x_range.start_bound() {
+            Bound::Included(x) | Bound::Excluded(x) => *x,
+            Bound::Unbounded => f64::NEG_INFINITY,
+        };
+        let end = match x_range.end_bound() {
+            Bound::Included(x) | Bound::Excluded(x) => *x,
+            Bound::Unbounded => f64::INFINITY,
+        };
+        let x_range = start..=end;
+
+        let generator = ExplicitGenerator {
+            function: Box::new(function),
+            x_range,
+            points,
+        };
+
+        Self {
+            values: Vec::new(),
+            generator: Some(generator),
+        }
+    }
+
+    /// Draw a line based on a function `(x,y)=f(t)`, a range for t and the number of points.
+    /// The range may be specified as start..end or as start..=end.
+    pub fn from_parametric_callback(
+        function: impl Fn(f64) -> (f64, f64),
+        t_range: impl RangeBounds<f64>,
+        points: usize,
+    ) -> Self {
+        let start = match t_range.start_bound() {
+            Bound::Included(x) => x,
+            Bound::Excluded(_) => unreachable!(),
+            Bound::Unbounded => panic!("The range for parametric functions must be bounded!"),
+        };
+        let end = match t_range.end_bound() {
+            Bound::Included(x) | Bound::Excluded(x) => x,
+            Bound::Unbounded => panic!("The range for parametric functions must be bounded!"),
+        };
+        let last_point_included = matches!(t_range.end_bound(), Bound::Included(_));
+        let increment = if last_point_included {
+            (end - start) / (points - 1) as f64
+        } else {
+            (end - start) / points as f64
+        };
+        let values = (0..points).map(|i| {
+            let t = start + i as f64 * increment;
+            let (x, y) = function(t);
+            Value { x, y }
+        });
+        Self::from_values_iter(values)
+    }
+
+    /// From a series of y-values.
+    /// The x-values will be the indices of these values
+    pub fn from_ys_f32(ys: &[f32]) -> Self {
+        let values: Vec<Value> = ys
+            .iter()
+            .enumerate()
+            .map(|(i, &y)| Value {
+                x: i as f64,
+                y: y as f64,
+            })
+            .collect();
+        Self::from_values(values)
+    }
+
+    /// Returns true if there are no data points available and there is no function to generate any.
+    pub(crate) fn is_empty(&self) -> bool {
+        self.generator.is_none() && self.values.is_empty()
+    }
+
+    /// If initialized with a generator function, this will generate `n` evenly spaced points in the
+    /// given range.
+    pub(super) fn generate_points(&mut self, x_range: RangeInclusive<f64>) {
+        if let Some(generator) = self.generator.take() {
+            if let Some(intersection) = Self::range_intersection(&x_range, &generator.x_range) {
+                let increment =
+                    (intersection.end() - intersection.start()) / (generator.points - 1) as f64;
+                self.values = (0..generator.points)
+                    .map(|i| {
+                        let x = intersection.start() + i as f64 * increment;
+                        let y = (generator.function)(x);
+                        Value { x, y }
+                    })
+                    .collect();
+            }
+        }
+    }
+
+    /// Returns the intersection of two ranges if they intersect.
+    fn range_intersection(
+        range1: &RangeInclusive<f64>,
+        range2: &RangeInclusive<f64>,
+    ) -> Option<RangeInclusive<f64>> {
+        let start = range1.start().max(*range2.start());
+        let end = range1.end().min(*range2.end());
+        (start < end).then(|| start..=end)
+    }
+
+    pub(super) fn get_bounds(&self) -> PlotBounds {
+        let mut bounds = PlotBounds::NOTHING;
+        self.values
+            .iter()
+            .for_each(|value| bounds.extend_with(value));
+        bounds
+    }
+}
+
+// ----------------------------------------------------------------------------
+
+#[derive(Debug, PartialEq, Eq, Clone, Copy)]
+pub enum MarkerShape {
+    Circle,
+    Diamond,
+    Square,
+    Cross,
+    Plus,
+    Up,
+    Down,
+    Left,
+    Right,
+    Asterisk,
+}
+
+impl MarkerShape {
+    /// Get a vector containing all marker shapes.
+    pub fn all() -> impl Iterator<Item = MarkerShape> {
+        [
+            Self::Circle,
+            Self::Diamond,
+            Self::Square,
+            Self::Cross,
+            Self::Plus,
+            Self::Up,
+            Self::Down,
+            Self::Left,
+            Self::Right,
+            Self::Asterisk,
+        ]
+        .iter()
+        .copied()
+    }
+}
+
+// ----------------------------------------------------------------------------
+
+/// Query the values of the plot, for geometric relations like closest checks
+pub(crate) enum PlotGeometry<'a> {
+    /// No geometry based on single elements (examples: text, image, horizontal/vertical line)
+    None,
+
+    /// Point values (X-Y graphs)
+    Points(&'a [Value]),
+
+    /// Rectangles (examples: boxes or bars)
+    // Has currently no data, as it would require copying rects or iterating a list of pointers.
+    // Instead, geometry-based functions are directly implemented in the respective PlotItem impl.
+    Rects,
+}
+
+// ----------------------------------------------------------------------------
+
+/// Describes a function y = f(x) with an optional range for x and a number of points.
+struct ExplicitGenerator {
+    function: Box<dyn Fn(f64) -> f64>,
+    x_range: RangeInclusive<f64>,
+    points: usize,
+}
+
+// ----------------------------------------------------------------------------
+
+/// Result of [`PlotItem::find_closest()`] search, identifies an element inside the item for immediate use
+pub(crate) struct ClosestElem {
+    /// Position of hovered-over value (or bar/box-plot/...) in PlotItem
+    pub index: usize,
+
+    /// Squared distance from the mouse cursor (needed to compare against other PlotItems, which might be nearer)
+    pub dist_sq: f32,
+}

egui/src/widgets/plot/mod.rs

@@ -1,23 +1,23 @@
 //! Simple plotting library.
 
+use crate::util::float_ord::FloatOrd;
+use crate::*;
+use color::Hsva;
+use epaint::ahash::AHashSet;
+use items::PlotItem;
+use legend::LegendWidget;
+use transform::{PlotBounds, ScreenTransform};
+
+pub use items::{
+    Arrows, Bar, BarChart, BoxElem, BoxPlot, BoxSpread, HLine, Line, LineStyle, MarkerShape,
+    PlotImage, Points, Polygon, Text, VLine, Value, Values,
+};
+pub use legend::{Corner, Legend};
+
 mod items;
 mod legend;
 mod transform;
 
-use items::PlotItem;
-pub use items::{
-    Arrows, HLine, Line, LineStyle, MarkerShape, PlotImage, Points, Polygon, Text, VLine, Value,
-    Values,
-};
-use legend::LegendWidget;
-pub use legend::{Corner, Legend};
-pub use transform::PlotBounds;
-use transform::ScreenTransform;
-
-use crate::*;
-use color::Hsva;
-use epaint::ahash::AHashSet;
-
 // ----------------------------------------------------------------------------
 
 /// Information about the plot that has to persist between frames.
@@ -581,6 +581,32 @@ impl PlotUi {
         }
         self.items.push(Box::new(vline));
     }
+
+    /// Add a box plot diagram.
+    pub fn box_plot(&mut self, mut box_plot: BoxPlot) {
+        if box_plot.boxes.is_empty() {
+            return;
+        }
+
+        // Give the elements an automatic color if no color has been assigned.
+        if box_plot.default_color == Color32::TRANSPARENT {
+            box_plot = box_plot.color(self.auto_color());
+        }
+        self.items.push(Box::new(box_plot));
+    }
+
+    /// Add a bar chart.
+    pub fn bar_chart(&mut self, mut chart: BarChart) {
+        if chart.bars.is_empty() {
+            return;
+        }
+
+        // Give the elements an automatic color if no color has been assigned.
+        if chart.default_color == Color32::TRANSPARENT {
+            chart = chart.color(self.auto_color());
+        }
+        self.items.push(Box::new(chart));
+    }
 }
 
 struct PreparedPlot {
@@ -713,88 +739,31 @@ impl PreparedPlot {
             return;
         }
 
-        let interact_radius: f32 = 16.0;
-        let mut closest_value = None;
-        let mut closest_item = None;
-        let mut closest_dist_sq = interact_radius.powi(2);
-        for item in items {
-            if let Some(values) = item.values() {
-                for value in &values.values {
-                    let pos = transform.position_from_value(value);
-                    let dist_sq = pointer.distance_sq(pos);
-                    if dist_sq < closest_dist_sq {
-                        closest_dist_sq = dist_sq;
-                        closest_value = Some(value);
-                        closest_item = Some(item.name());
-                    }
-                }
-            }
-        }
+        let interact_radius_sq: f32 = (16.0f32).powi(2);
 
-        let mut prefix = String::new();
-        if let Some(name) = closest_item {
-            if !name.is_empty() {
-                prefix = format!("{}\n", name);
-            }
-        }
+        let candidates = items.iter().filter_map(|item| {
+            let item = &**item;
+            let closest = item.find_closest(pointer, transform);
 
-        let line_color = if ui.visuals().dark_mode {
-            Color32::from_gray(100).additive()
-        } else {
-            Color32::from_black_alpha(180)
+            Some(item).zip(closest)
+        });
+
+        let closest = candidates
+            .min_by_key(|(_, elem)| elem.dist_sq.ord())
+            .filter(|(_, elem)| elem.dist_sq <= interact_radius_sq);
+
+        let plot = items::PlotConfig {
+            ui,
+            transform,
+            show_x: *show_x,
+            show_y: *show_y,
         };
 
-        let value = if let Some(value) = closest_value {
-            let position = transform.position_from_value(value);
-            shapes.push(Shape::circle_filled(position, 3.0, line_color));
-            *value
+        if let Some((item, elem)) = closest {
+            item.on_hover(elem, shapes, &plot);
         } else {
-            transform.value_from_position(pointer)
-        };
-        let pointer = transform.position_from_value(&value);
-
-        let rect = transform.frame();
-
-        if *show_x {
-            // vertical line
-            shapes.push(Shape::line_segment(
-                [pos2(pointer.x, rect.top()), pos2(pointer.x, rect.bottom())],
-                (1.0, line_color),
-            ));
+            let value = transform.value_from_position(pointer);
+            items::rulers_at_value(pointer, value, "", &plot, shapes);
         }
-        if *show_y {
-            // horizontal line
-            shapes.push(Shape::line_segment(
-                [pos2(rect.left(), pointer.y), pos2(rect.right(), pointer.y)],
-                (1.0, line_color),
-            ));
-        }
-
-        let text = {
-            let scale = transform.dvalue_dpos();
-            let x_decimals = ((-scale[0].abs().log10()).ceil().at_least(0.0) as usize).at_most(6);
-            let y_decimals = ((-scale[1].abs().log10()).ceil().at_least(0.0) as usize).at_most(6);
-            if *show_x && *show_y {
-                format!(
-                    "{}x = {:.*}\ny = {:.*}",
-                    prefix, x_decimals, value.x, y_decimals, value.y
-                )
-            } else if *show_x {
-                format!("{}x = {:.*}", prefix, x_decimals, value.x)
-            } else if *show_y {
-                format!("{}y = {:.*}", prefix, y_decimals, value.y)
-            } else {
-                unreachable!()
-            }
-        };
-
-        shapes.push(Shape::text(
-            ui.fonts(),
-            pointer + vec2(3.0, -2.0),
-            Align2::LEFT_BOTTOM,
-            text,
-            TextStyle::Body,
-            ui.visuals().text_color(),
-        ));
     }
 }

egui/src/widgets/plot/transform.rs

@@ -52,6 +52,14 @@ impl PlotBounds {
         self.max[1] - self.min[1]
     }
 
+    pub fn center(&self) -> Value {
+        Value {
+            x: (self.min[0] + self.max[0]) / 2.0,
+            y: (self.min[1] + self.max[1]) / 2.0,
+        }
+    }
+
+    /// Expand to include the given (x,y) value
     pub(crate) fn extend_with(&mut self, value: &Value) {
         self.extend_with_x(value.x);
         self.extend_with_y(value.y);
@@ -225,6 +233,20 @@ impl ScreenTransform {
         Value::new(x, y)
     }
 
+    /// Transform a rectangle of plot values to a screen-coordinate rectangle.
+    ///
+    /// This typically means that the rect is mirrored vertically (top becomes bottom and vice versa),
+    /// since the plot's coordinate system has +Y up, while egui has +Y down.
+    pub fn rect_from_values(&self, value1: &Value, value2: &Value) -> Rect {
+        let pos1 = self.position_from_value(value1);
+        let pos2 = self.position_from_value(value2);
+
+        let mut rect = Rect::NOTHING;
+        rect.extend_with(pos1);
+        rect.extend_with(pos2);
+        rect
+    }
+
     /// delta position / delta value
     pub fn dpos_dvalue_x(&self) -> f64 {
         self.frame.width() as f64 / self.bounds.width()

egui_demo_lib/src/apps/demo/plot_demo.rs

@@ -1,9 +1,10 @@
+use std::f64::consts::TAU;
+
 use egui::*;
 use plot::{
-    Arrows, Corner, HLine, Legend, Line, LineStyle, MarkerShape, Plot, PlotImage, Points, Polygon,
-    Text, VLine, Value, Values,
+    Arrows, Bar, BarChart, BoxElem, BoxPlot, BoxSpread, Corner, HLine, Legend, Line, LineStyle,
+    MarkerShape, Plot, PlotImage, Points, Polygon, Text, VLine, Value, Values,
 };
-use std::f64::consts::TAU;
 
 #[derive(PartialEq)]
 struct LineDemo {
@@ -430,18 +431,203 @@ impl Widget for &mut InteractionDemo {
     }
 }
 
+#[derive(PartialEq, Eq)]
+enum Chart {
+    GaussBars,
+    StackedBars,
+    BoxPlot,
+}
+
+impl Default for Chart {
+    fn default() -> Self {
+        Self::GaussBars
+    }
+}
+
+#[derive(PartialEq)]
+struct ChartsDemo {
+    chart: Chart,
+    vertical: bool,
+}
+
+impl Default for ChartsDemo {
+    fn default() -> Self {
+        Self {
+            vertical: true,
+            chart: Chart::default(),
+        }
+    }
+}
+
+impl ChartsDemo {
+    fn bar_gauss(&self, ui: &mut Ui) -> Response {
+        let mut chart = BarChart::new(
+            (-395..=395)
+                .step_by(10)
+                .map(|x| x as f64 * 0.01)
+                .map(|x| {
+                    (
+                        x,
+                        (-x * x / 2.0).exp() / (2.0 * std::f64::consts::PI).sqrt(),
+                    )
+                })
+                // The 10 factor here is purely for a nice 1:1 aspect ratio
+                .map(|(x, f)| Bar::new(x, f * 10.0).width(0.095))
+                .collect(),
+        )
+        .color(Color32::LIGHT_BLUE)
+        .name("Normal Distribution");
+        if !self.vertical {
+            chart = chart.horizontal();
+        }
+
+        Plot::new("Normal Distribution Demo")
+            .legend(Legend::default())
+            .data_aspect(1.0)
+            .show(ui, |plot_ui| plot_ui.bar_chart(chart))
+            .response
+    }
+
+    fn bar_stacked(&self, ui: &mut Ui) -> Response {
+        let mut chart1 = BarChart::new(vec![
+            Bar::new(0.5, 1.0).name("Day 1"),
+            Bar::new(1.5, 3.0).name("Day 2"),
+            Bar::new(2.5, 1.0).name("Day 3"),
+            Bar::new(3.5, 2.0).name("Day 4"),
+            Bar::new(4.5, 4.0).name("Day 5"),
+        ])
+        .width(0.7)
+        .name("Set 1");
+
+        let mut chart2 = BarChart::new(vec![
+            Bar::new(0.5, 1.0),
+            Bar::new(1.5, 1.5),
+            Bar::new(2.5, 0.1),
+            Bar::new(3.5, 0.7),
+            Bar::new(4.5, 0.8),
+        ])
+        .width(0.7)
+        .name("Set 2")
+        .stack_on(&[&chart1]);
+
+        let mut chart3 = BarChart::new(vec![
+            Bar::new(0.5, -0.5),
+            Bar::new(1.5, 1.0),
+            Bar::new(2.5, 0.5),
+            Bar::new(3.5, -1.0),
+            Bar::new(4.5, 0.3),
+        ])
+        .width(0.7)
+        .name("Set 3")
+        .stack_on(&[&chart1, &chart2]);
+
+        let mut chart4 = BarChart::new(vec![
+            Bar::new(0.5, 0.5),
+            Bar::new(1.5, 1.0),
+            Bar::new(2.5, 0.5),
+            Bar::new(3.5, -0.5),
+            Bar::new(4.5, -0.5),
+        ])
+        .width(0.7)
+        .name("Set 4")
+        .stack_on(&[&chart1, &chart2, &chart3]);
+
+        if !self.vertical {
+            chart1 = chart1.horizontal();
+            chart2 = chart2.horizontal();
+            chart3 = chart3.horizontal();
+            chart4 = chart4.horizontal();
+        }
+
+        Plot::new("Stacked Bar Chart Demo")
+            .legend(Legend::default())
+            .data_aspect(1.0)
+            .show(ui, |plot_ui| {
+                plot_ui.bar_chart(chart1);
+                plot_ui.bar_chart(chart2);
+                plot_ui.bar_chart(chart3);
+                plot_ui.bar_chart(chart4);
+            })
+            .response
+    }
+
+    fn box_plot(&self, ui: &mut Ui) -> Response {
+        let yellow = Color32::from_rgb(248, 252, 168);
+        let mut box1 = BoxPlot::new(vec![
+            BoxElem::new(0.5, BoxSpread::new(1.5, 2.2, 2.5, 2.6, 3.1)).name("Day 1"),
+            BoxElem::new(2.5, BoxSpread::new(0.4, 1.0, 1.1, 1.4, 2.1)).name("Day 2"),
+            BoxElem::new(4.5, BoxSpread::new(1.7, 2.0, 2.2, 2.5, 2.9)).name("Day 3"),
+        ])
+        .name("Experiment A");
+
+        let mut box2 = BoxPlot::new(vec![
+            BoxElem::new(1.0, BoxSpread::new(0.2, 0.5, 1.0, 2.0, 2.7)).name("Day 1"),
+            BoxElem::new(3.0, BoxSpread::new(1.5, 1.7, 2.1, 2.9, 3.3))
+                .name("Day 2: interesting")
+                .stroke(Stroke::new(1.5, yellow))
+                .fill(yellow.linear_multiply(0.2)),
+            BoxElem::new(5.0, BoxSpread::new(1.3, 2.0, 2.3, 2.9, 4.0)).name("Day 3"),
+        ])
+        .name("Experiment B");
+
+        let mut box3 = BoxPlot::new(vec![
+            BoxElem::new(1.5, BoxSpread::new(2.1, 2.2, 2.6, 2.8, 3.0)).name("Day 1"),
+            BoxElem::new(3.5, BoxSpread::new(1.3, 1.5, 1.9, 2.2, 2.4)).name("Day 2"),
+            BoxElem::new(5.5, BoxSpread::new(0.2, 0.4, 1.0, 1.3, 1.5)).name("Day 3"),
+        ])
+        .name("Experiment C");
+
+        if !self.vertical {
+            box1 = box1.horizontal();
+            box2 = box2.horizontal();
+            box3 = box3.horizontal();
+        }
+
+        Plot::new("Box Plot Demo")
+            .legend(Legend::default())
+            .show(ui, |plot_ui| {
+                plot_ui.box_plot(box1);
+                plot_ui.box_plot(box2);
+                plot_ui.box_plot(box3);
+            })
+            .response
+    }
+}
+
+impl Widget for &mut ChartsDemo {
+    fn ui(self, ui: &mut Ui) -> Response {
+        ui.label("Type:");
+        ui.horizontal(|ui| {
+            ui.selectable_value(&mut self.chart, Chart::GaussBars, "Histogram");
+            ui.selectable_value(&mut self.chart, Chart::StackedBars, "Stacked Bar Chart");
+            ui.selectable_value(&mut self.chart, Chart::BoxPlot, "Box Plot");
+        });
+        ui.label("Orientation:");
+        ui.horizontal(|ui| {
+            ui.selectable_value(&mut self.vertical, true, "Vertical");
+            ui.selectable_value(&mut self.vertical, false, "Horizontal");
+        });
+        match self.chart {
+            Chart::GaussBars => self.bar_gauss(ui),
+            Chart::StackedBars => self.bar_stacked(ui),
+            Chart::BoxPlot => self.box_plot(ui),
+        }
+    }
+}
+
 #[derive(PartialEq, Eq)]
 enum Panel {
     Lines,
     Markers,
     Legend,
+    Charts,
     Items,
     Interaction,
 }
 
 impl Default for Panel {
     fn default() -> Self {
-        Self::Lines
+        Self::Charts
     }
 }
 
@@ -450,6 +636,7 @@ pub struct PlotDemo {
     line_demo: LineDemo,
     marker_demo: MarkerDemo,
     legend_demo: LegendDemo,
+    charts_demo: ChartsDemo,
     items_demo: ItemsDemo,
     interaction_demo: InteractionDemo,
     open_panel: Panel,
@@ -492,6 +679,7 @@ impl super::View for PlotDemo {
             ui.selectable_value(&mut self.open_panel, Panel::Lines, "Lines");
             ui.selectable_value(&mut self.open_panel, Panel::Markers, "Markers");
             ui.selectable_value(&mut self.open_panel, Panel::Legend, "Legend");
+            ui.selectable_value(&mut self.open_panel, Panel::Charts, "Charts");
             ui.selectable_value(&mut self.open_panel, Panel::Items, "Items");
             ui.selectable_value(&mut self.open_panel, Panel::Interaction, "Interaction");
         });
@@ -507,6 +695,9 @@ impl super::View for PlotDemo {
             Panel::Legend => {
                 ui.add(&mut self.legend_demo);
             }
+            Panel::Charts => {
+                ui.add(&mut self.charts_demo);
+            }
             Panel::Items => {
                 ui.add(&mut self.items_demo);
             }

emath/src/rect.rs

@@ -309,6 +309,27 @@ impl Rect {
         self.width() * self.height()
     }
 
+    #[inline]
+    pub fn distance_sq_to_pos(&self, pos: Pos2) -> f32 {
+        let dx = if self.min.x > pos.x {
+            self.min.x - pos.x
+        } else if pos.x > self.max.x {
+            pos.x - self.max.x
+        } else {
+            0.0
+        };
+
+        let dy = if self.min.y > pos.y {
+            self.min.y - pos.y
+        } else if pos.y > self.max.y {
+            pos.y - self.max.y
+        } else {
+            0.0
+        };
+
+        dx * dx + dy * dy
+    }
+
     #[inline(always)]
     pub fn x_range(&self) -> RangeInclusive<f32> {
         self.min.x..=self.max.x