Introduce type parameter for plot points

demo/src/plot_demo.rs

@@ -1,8 +1,10 @@
+use std::collections::HashMap;
 use std::ops::RangeInclusive;
 use std::{f64::consts::TAU, sync::Arc};
 
+use egui::mutex::Mutex;
 use egui::{
-    Checkbox, Color32, ComboBox, NumExt as _, Pos2, Response, ScrollArea, Stroke, TextWrapMode,
+    Checkbox, Color32, ComboBox, Id, NumExt as _, Pos2, Response, ScrollArea, Stroke, TextWrapMode,
     Vec2b, WidgetInfo, WidgetType, remap, vec2,
 };
 
@@ -24,6 +26,7 @@ enum Panel {
     Interaction,
     CustomAxes,
     LinkedAxes,
+    Userdata,
 }
 
 impl Default for Panel {
@@ -44,6 +47,7 @@ pub struct PlotDemo {
     interaction_demo: InteractionDemo,
     custom_axes_demo: CustomAxesDemo,
     linked_axes_demo: LinkedAxesDemo,
+    userdata_demo: UserdataDemo,
     open_panel: Panel,
 }
 
@@ -124,6 +128,7 @@ impl PlotDemo {
             ui.selectable_value(&mut self.open_panel, Panel::Interaction, "Interaction");
             ui.selectable_value(&mut self.open_panel, Panel::CustomAxes, "Custom Axes");
             ui.selectable_value(&mut self.open_panel, Panel::LinkedAxes, "Linked Axes");
+            ui.selectable_value(&mut self.open_panel, Panel::Userdata, "Userdata");
         });
         ui.separator();
 
@@ -152,6 +157,9 @@ impl PlotDemo {
             Panel::LinkedAxes => {
                 self.linked_axes_demo.ui(ui);
             }
+            Panel::Userdata => {
+                self.userdata_demo.ui(ui);
+            }
         }
     }
 }
@@ -642,7 +650,7 @@ impl CustomAxesDemo {
             }
         };
 
-        let label_fmt = |_s: &str, val: &PlotPoint| {
+        let label_fmt = |_s: &str, val: &PlotPoint, _| {
             format!(
                 "Day {d}, {h}:{m:02}\n{p:.2}%",
                 d = day(val.x),
@@ -1197,6 +1205,145 @@ impl ChartsDemo {
     }
 }
 
+#[derive(PartialEq, serde::Deserialize, serde::Serialize, Default)]
+struct UserdataDemo {}
+
+#[derive(Clone)]
+struct DemoPoint {
+    x: f64,
+    y: f64,
+    custom_label: String,
+    importance: f32,
+}
+
+impl UserdataDemo {
+    #[expect(clippy::unused_self, clippy::significant_drop_tightening)]
+    fn ui(&self, ui: &mut egui::Ui) -> Response {
+        ui.label(
+            "This demo shows how to attach custom data to plot items and display it in tooltips.",
+        );
+        ui.separator();
+
+        // Create multiple datasets with custom metadata
+        let sine_points = (0..=500)
+            .map(|i| {
+                let x = i as f64 / 100.0;
+                DemoPoint {
+                    x,
+                    y: x.sin(),
+                    custom_label: format!("Sine #{i}"),
+                    importance: (i % 100) as f32 / 100.0,
+                }
+            })
+            .collect::<Vec<_>>();
+
+        let cosine_points = (0..=500)
+            .map(|i| {
+                let x = i as f64 / 100.0;
+                DemoPoint {
+                    x,
+                    y: x.cos(),
+                    custom_label: format!("Cosine #{i}"),
+                    importance: (1.0 - (i % 100) as f32 / 100.0),
+                }
+            })
+            .collect::<Vec<_>>();
+
+        let damped_points = (0..=500)
+            .map(|i| {
+                let x = i as f64 / 100.0;
+                DemoPoint {
+                    x,
+                    y: (-x * 0.5).exp() * (2.0 * x).sin(),
+                    custom_label: format!("Damped #{i}"),
+                    importance: if i % 50 == 0 { 1.0 } else { 0.3 },
+                }
+            })
+            .collect::<Vec<_>>();
+
+        // Store custom data in a shared map
+        let custom_data = Arc::new(Mutex::new(HashMap::<Id, Vec<DemoPoint>>::new()));
+
+        let custom_data_ = custom_data.clone();
+        Plot::new("Userdata Plot Demo")
+            .legend(Legend::default().position(Corner::LeftTop))
+            .label_formatter(move |name, value, item| {
+                if let Some((id, index)) = item {
+                    let lock = custom_data_.lock();
+                    if let Some(points) = lock.get(&id) {
+                        if let Some(point) = points.get(index) {
+                            return format!(
+                                "{}\nPosition: ({:.3}, {:.3})\nLabel: {}\nImportance: {:.1}%",
+                                name,
+                                value.x,
+                                value.y,
+                                point.custom_label,
+                                point.importance * 100.0
+                            );
+                        }
+                    }
+                }
+                format!("{}\n({:.3}, {:.3})", name, value.x, value.y)
+            })
+            .show(ui, |plot_ui| {
+                let mut lock = custom_data.lock();
+
+                // Sine wave with custom data
+                let sine_id = Id::new("sine_wave");
+                lock.insert(sine_id, sine_points.clone());
+                plot_ui.line(
+                    Line::new(
+                        "sin(x)",
+                        sine_points.iter().map(|p| [p.x, p.y]).collect::<Vec<_>>(),
+                    )
+                    .id(sine_id)
+                    .color(Color32::from_rgb(200, 100, 100)),
+                );
+
+                // Cosine wave with custom data
+                let cosine_id = Id::new("cosine_wave");
+                lock.insert(cosine_id, cosine_points.clone());
+                plot_ui.line(
+                    Line::new(
+                        "cos(x)",
+                        cosine_points.iter().map(|p| [p.x, p.y]).collect::<Vec<_>>(),
+                    )
+                    .id(cosine_id)
+                    .color(Color32::from_rgb(100, 200, 100)),
+                );
+
+                // Damped sine wave with custom data
+                let damped_id = Id::new("damped_wave");
+                lock.insert(damped_id, damped_points.clone());
+                plot_ui.line(
+                    Line::new(
+                        "e^(-0.5x) · sin(2x)",
+                        damped_points.iter().map(|p| [p.x, p.y]).collect::<Vec<_>>(),
+                    )
+                    .id(damped_id)
+                    .color(Color32::from_rgb(100, 100, 200)),
+                );
+
+                // Add some points with high importance as markers
+                let important_points: Vec<_> = damped_points
+                    .iter()
+                    .filter(|p| p.importance > 0.9)
+                    .map(|p| [p.x, p.y])
+                    .collect();
+
+                if !important_points.is_empty() {
+                    plot_ui.points(
+                        Points::new("Important Points", important_points)
+                            .color(Color32::from_rgb(255, 150, 0))
+                            .radius(4.0)
+                            .shape(MarkerShape::Diamond),
+                    );
+                }
+            })
+            .response
+    }
+}
+
 fn is_approx_zero(val: f64) -> bool {
     val.abs() < 1e-6
 }

egui_plot/src/items/mod.rs

@@ -143,7 +143,7 @@ pub trait PlotItem {
         match self.geometry() {
             PlotGeometry::None => None,
 
-            PlotGeometry::Points(points) => points
+            PlotGeometry::Points(points, _) => points
                 .iter()
                 .enumerate()
                 .map(|(index, value)| {
@@ -168,8 +168,8 @@ pub trait PlotItem {
         plot: &PlotConfig<'_>,
         label_formatter: &LabelFormatter<'_>,
     ) {
-        let points = match self.geometry() {
-            PlotGeometry::Points(points) => points,
+        let (points, id) = match self.geometry() {
+            PlotGeometry::Points(points, id) => (points, id),
             PlotGeometry::None => {
                 panic!("If the PlotItem has no geometry, on_hover() must not be called")
             }
@@ -192,6 +192,7 @@ pub trait PlotItem {
         rulers_and_tooltip_at_value(
             plot_area_response,
             value,
+            id.map(|id| (id, elem.index)),
             self.name(),
             plot,
             cursors,
@@ -603,7 +604,7 @@ impl PlotItem for Line<'_> {
     }
 
     fn geometry(&self) -> PlotGeometry<'_> {
-        PlotGeometry::Points(self.series.points())
+        PlotGeometry::Points(self.series.points(), Some(self.id()))
     }
 
     fn bounds(&self) -> PlotBounds {
@@ -705,7 +706,7 @@ impl PlotItem for Polygon<'_> {
     }
 
     fn geometry(&self) -> PlotGeometry<'_> {
-        PlotGeometry::Points(self.series.points())
+        PlotGeometry::Points(self.series.points(), Some(self.id()))
     }
 
     fn bounds(&self) -> PlotBounds {
@@ -1025,7 +1026,7 @@ impl PlotItem for Points<'_> {
     }
 
     fn geometry(&self) -> PlotGeometry<'_> {
-        PlotGeometry::Points(self.series.points())
+        PlotGeometry::Points(self.series.points(), Some(self.id()))
     }
 
     fn bounds(&self) -> PlotBounds {
@@ -1136,7 +1137,7 @@ impl PlotItem for Arrows<'_> {
     }
 
     fn geometry(&self) -> PlotGeometry<'_> {
-        PlotGeometry::Points(self.origins.points())
+        PlotGeometry::Points(self.origins.points(), Some(self.id()))
     }
 
     fn bounds(&self) -> PlotBounds {
@@ -1705,6 +1706,7 @@ fn add_rulers_and_text(
 pub(super) fn rulers_and_tooltip_at_value(
     plot_area_response: &egui::Response,
     value: PlotPoint,
+    item: Option<(Id, usize)>,
     name: &str,
     plot: &PlotConfig<'_>,
     cursors: &mut Vec<Cursor>,
@@ -1718,7 +1720,7 @@ pub(super) fn rulers_and_tooltip_at_value(
     }
 
     let text = if let Some(custom_label) = label_formatter {
-        let label = custom_label(name, &value);
+        let label = custom_label(name, &value, None);
         if label.is_empty() {
             return;
         }
@@ -1732,7 +1734,9 @@ pub(super) fn rulers_and_tooltip_at_value(
         let scale = plot.transform.dvalue_dpos();
         let x_decimals = ((-scale[0].abs().log10()).ceil().at_least(0.0) as usize).clamp(1, 6);
         let y_decimals = ((-scale[1].abs().log10()).ceil().at_least(0.0) as usize).clamp(1, 6);
-        if plot.show_x && plot.show_y {
+        if let Some(custom_label) = label_formatter {
+            custom_label(name, &value, item)
+        } else if plot.show_x && plot.show_y {
             format!(
                 "{}x = {:.*}\ny = {:.*}",
                 prefix, x_decimals, value.x, y_decimals, value.y

egui_plot/src/items/values.rs

@@ -1,7 +1,7 @@
 use std::ops::{Bound, RangeBounds, RangeInclusive};
 
 use egui::{
-    Pos2, Rect, Shape, Stroke, Vec2,
+    Id, Pos2, Rect, Shape, Stroke, Vec2,
     epaint::{ColorMode, PathStroke},
     lerp, pos2,
 };
@@ -397,7 +397,7 @@ pub enum PlotGeometry<'a> {
     None,
 
     /// Point values (X-Y graphs)
-    Points(&'a [PlotPoint]),
+    Points(&'a [PlotPoint], Option<Id>),
 
     /// Rectangles (examples: boxes or bars)
     // Has currently no data, as it would require copying rects or iterating a list of pointers.