Add optional legend title

demo/src/plot_demo.rs

@@ -326,7 +326,7 @@ impl LineDemo {
             self.time += ui.input(|i| i.unstable_dt).at_most(1.0 / 30.0) as f64;
         };
         let mut plot = Plot::new("lines_demo")
-            .legend(Legend::default())
+            .legend(Legend::default().title("Lines"))
             .show_axes(self.show_axes)
             .show_grid(self.show_grid);
         if self.square {
@@ -417,7 +417,7 @@ impl MarkerDemo {
 
         let markers_plot = Plot::new("markers_demo")
             .data_aspect(1.0)
-            .legend(Legend::default());
+            .legend(Legend::default().title("Markers"));
         markers_plot
             .show(ui, |plot_ui| {
                 for marker in self.markers() {
@@ -805,7 +805,11 @@ impl ItemsDemo {
         );
 
         let plot = Plot::new("items_demo")
-            .legend(Legend::default().position(Corner::RightBottom))
+            .legend(
+                Legend::default()
+                    .position(Corner::RightBottom)
+                    .title("Items"),
+            )
             .show_x(false)
             .show_y(false)
             .data_aspect(1.0);

demo/tests/plot.rs

@@ -16,7 +16,7 @@ fn test_demos() {
     let mut errors = Vec::new();
 
     for name in demo_names {
-        harness.get_by_label(&name).click();
+        harness.get_by_role_and_label(Role::Button, &name).click();
         harness.run();
 
         if let Err(error) = harness.try_snapshot(&format!("demos/{name}")) {

egui_plot/src/legend.rs

@@ -46,6 +46,7 @@ pub struct Legend {
     pub text_style: TextStyle,
     pub background_alpha: f32,
     pub position: Corner,
+    pub title: Option<String>,
 
     follow_insertion_order: bool,
     color_conflict_handling: ColorConflictHandling,
@@ -60,6 +61,7 @@ impl Default for Legend {
             text_style: TextStyle::Body,
             background_alpha: 0.75,
             position: Corner::RightTop,
+            title: None,
             follow_insertion_order: false,
             color_conflict_handling: ColorConflictHandling::RemoveColor,
             hidden_items: None,
@@ -89,6 +91,13 @@ impl Legend {
         self
     }
 
+    /// Set the title of the legend. Default: `None`.
+    #[inline]
+    pub fn title(mut self, title: &str) -> Self {
+        self.title = Some(title.to_owned());
+        self
+    }
+
     /// Specifies hidden items in the legend configuration to override the existing ones. This
     /// allows the legend traces' visibility to be controlled from the application code.
     #[inline]
@@ -329,6 +338,12 @@ impl Widget for &mut LegendWidget {
                 .multiply_with_opacity(config.background_alpha);
                 background_frame
                     .show(ui, |ui| {
+                        // always show on top of the legend - so we need to use a new scope
+                        if main_dir == Direction::TopDown {
+                            if let Some(title) = &config.title {
+                                ui.heading(title);
+                            }
+                        }
                         let mut focus_on_item = None;
 
                         let response_union = entries
@@ -348,6 +363,12 @@ impl Widget for &mut LegendWidget {
                             .reduce(|r1, r2| r1.union(r2))
                             .expect("No entries in the legend");
 
+                        if main_dir == Direction::BottomUp {
+                            if let Some(title) = &config.title {
+                                ui.heading(title);
+                            }
+                        }
+
                         if let Some(focus_on_item) = focus_on_item {
                             handle_focus_on_legend_item(&focus_on_item, entries);
                         }