Introduce type parameter for plot points

demo/src/plot_demo.rs

@@ -2,7 +2,7 @@ use std::f64::consts::TAU;
 use std::ops::RangeInclusive;
 
 use egui::{
-    remap, vec2, Color32, ComboBox, NumExt, Pos2, Response, ScrollArea, Stroke, TextWrapMode,
+    remap, vec2, Color32, ComboBox, Id, NumExt, Pos2, Response, ScrollArea, Stroke, TextWrapMode,
     Vec2b, WidgetInfo, WidgetType,
 };
 
@@ -24,6 +24,7 @@ enum Panel {
     Interaction,
     CustomAxes,
     LinkedAxes,
+    Userdata,
 }
 
 impl Default for Panel {
@@ -44,6 +45,7 @@ pub struct PlotDemo {
     interaction_demo: InteractionDemo,
     custom_axes_demo: CustomAxesDemo,
     linked_axes_demo: LinkedAxesDemo,
+    userdata_demo: UserdataDemo,
     open_panel: Panel,
 }
 
@@ -88,6 +90,7 @@ 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();
@@ -117,6 +120,9 @@ impl PlotDemo {
             Panel::LinkedAxes => {
                 self.linked_axes_demo.ui(ui);
             }
+            Panel::Userdata => {
+                self.userdata_demo.ui(ui);
+            }
         }
     }
 }
@@ -565,7 +571,7 @@ 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),
@@ -1101,6 +1107,61 @@ impl ChartsDemo {
     }
 }
 
+#[derive(PartialEq, serde::Deserialize, serde::Serialize, Default)]
+struct UserdataDemo {}
+
+struct DemoPoint {
+    x: f64,
+    y: f64,
+    custom_thing: bool,
+}
+
+impl UserdataDemo {
+    #[allow(clippy::unused_self, clippy::significant_drop_tightening)]
+    fn ui(&self, ui: &mut egui::Ui) -> Response {
+        let points = (1..=1000)
+            .map(|i| DemoPoint {
+                x: i as f64 / 1000.0,
+                y: ((i as f64) / 1000.0 * std::f64::consts::PI * 2.0).sin(),
+                custom_thing: i % 2 == 0,
+            })
+            .collect::<Vec<_>>();
+
+        let custom_things =
+            std::sync::Arc::new(egui::mutex::Mutex::new(std::collections::HashMap::<
+                Id,
+                Vec<bool>,
+            >::new()));
+
+        let custom_things_ = custom_things.clone();
+        Plot::new("Userdata Plot Demo")
+            .legend(Legend::default())
+            .label_formatter(|_, _, item| {
+                format!(
+                    "item: {:?}\ncustom_thing: {:?}",
+                    item,
+                    item.and_then(|(id, index)| custom_things_
+                        .lock()
+                        .get(&id)
+                        .and_then(|vec| vec.get(index).copied()))
+                )
+            })
+            .show(ui, |plot_ui| {
+                let id = Id::new(1234);
+                let mut lock = custom_things.lock();
+                let entry = lock.entry(id).or_default();
+
+                for p in &points {
+                    entry.push(p.custom_thing);
+                }
+
+                plot_ui
+                    .line(Line::new(points.iter().map(|p| [p.x, p.y]).collect::<Vec<_>>()).id(id));
+            })
+            .response
+    }
+}
+
 fn is_approx_zero(val: f64) -> bool {
     val.abs() < 1e-6
 }

egui_plot/src/items/mod.rs

@@ -64,7 +64,7 @@ pub trait PlotItem {
         match self.geometry() {
             PlotGeometry::None => None,
 
-            PlotGeometry::Points(points) => points
+            PlotGeometry::Points(points, _) => points
                 .iter()
                 .enumerate()
                 .map(|(index, value)| {
@@ -88,8 +88,8 @@ 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")
             }
@@ -112,6 +112,7 @@ pub trait PlotItem {
         rulers_at_value(
             pointer,
             value,
+            id.map(|id| (id, elem.index)),
             self.name(),
             plot,
             shapes,
@@ -606,7 +607,7 @@ impl<'a> PlotItem for Line<'a> {
     }
 
     fn geometry(&self) -> PlotGeometry<'_> {
-        PlotGeometry::Points(self.series.points())
+        PlotGeometry::Points(self.series.points(), self.id())
     }
 
     fn bounds(&self) -> PlotBounds {
@@ -762,7 +763,7 @@ impl<'a> PlotItem for Polygon<'a> {
     }
 
     fn geometry(&self) -> PlotGeometry<'_> {
-        PlotGeometry::Points(self.series.points())
+        PlotGeometry::Points(self.series.points(), self.id())
     }
 
     fn bounds(&self) -> PlotBounds {
@@ -1183,7 +1184,7 @@ impl<'a> PlotItem for Points<'a> {
     }
 
     fn geometry(&self) -> PlotGeometry<'_> {
-        PlotGeometry::Points(self.series.points())
+        PlotGeometry::Points(self.series.points(), self.id())
     }
 
     fn bounds(&self) -> PlotBounds {
@@ -1340,7 +1341,7 @@ impl<'a> PlotItem for Arrows<'a> {
     }
 
     fn geometry(&self) -> PlotGeometry<'_> {
-        PlotGeometry::Points(self.origins.points())
+        PlotGeometry::Points(self.origins.points(), self.id())
     }
 
     fn bounds(&self) -> PlotBounds {
@@ -2040,6 +2041,7 @@ fn add_rulers_and_text(
 pub(super) fn rulers_at_value(
     pointer: Pos2,
     value: PlotPoint,
+    item: Option<(Id, usize)>,
     name: &str,
     plot: &PlotConfig<'_>,
     shapes: &mut Vec<Shape>,
@@ -2064,7 +2066,7 @@ pub(super) fn rulers_at_value(
         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 let Some(custom_label) = label_formatter {
-            custom_label(name, &value)
+            custom_label(name, &value, item)
         } else if plot.show_x && plot.show_y {
             format!(
                 "{}x = {:.*}\ny = {:.*}",

egui_plot/src/items/values.rs

@@ -1,6 +1,6 @@
 use std::ops::{Bound, RangeBounds, RangeInclusive};
 
-use egui::{lerp, Pos2, Shape, Stroke, Vec2};
+use egui::{lerp, Id, Pos2, Shape, Stroke, Vec2};
 
 use crate::transform::PlotBounds;
 
@@ -382,7 +382,7 @@ 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.

egui_plot/src/lib.rs

@@ -41,7 +41,7 @@ use axis::AxisWidget;
 use items::{horizontal_line, rulers_color, vertical_line};
 use legend::LegendWidget;
 
-type LabelFormatterFn<'a> = dyn Fn(&str, &PlotPoint) -> String + 'a;
+type LabelFormatterFn<'a> = dyn Fn(&str, &PlotPoint, Option<(Id, usize)>) -> String + 'a;
 pub type LabelFormatter<'a> = Option<Box<LabelFormatterFn<'a>>>;
 
 type GridSpacerFn<'a> = dyn Fn(GridInput) -> Vec<GridMark> + 'a;
@@ -397,7 +397,7 @@ impl<'a> Plot<'a> {
     /// }).collect();
     /// let line = Line::new(sin);
     /// Plot::new("my_plot").view_aspect(2.0)
-    /// .label_formatter(|name, value| {
+    /// .label_formatter(|name, value, _| {
     ///     if !name.is_empty() {
     ///         format!("{}: {:.*}%", name, 1, value.y)
     ///     } else {
@@ -409,7 +409,7 @@ impl<'a> Plot<'a> {
     /// ```
     pub fn label_formatter(
         mut self,
-        label_formatter: impl Fn(&str, &PlotPoint) -> String + 'a,
+        label_formatter: impl Fn(&str, &PlotPoint, Option<(Id, usize)>) -> String + 'a,
     ) -> Self {
         self.label_formatter = Some(Box::new(label_formatter));
         self
@@ -1716,6 +1716,7 @@ impl<'a> PreparedPlot<'a> {
             items::rulers_at_value(
                 pointer,
                 value,
+                None,
                 "",
                 &plot,
                 shapes,