From cf012a69646d28ce7c5825a998aa969734ba4d37 Mon Sep 17 00:00:00 2001
From: York Xiang <bombless@126.com>
Date: Tue, 14 Oct 2025 09:31:26 +0800
Subject: [PATCH] Implement virtual element to allow elements to escape from
 auto bounds calculation

---
 egui_plot/src/items/mod.rs | 54 ++++++++++++++++++++++++++++++++++++++
 egui_plot/src/lib.rs       |  3 +++
 2 files changed, 57 insertions(+)

diff --git a/egui_plot/src/items/mod.rs b/egui_plot/src/items/mod.rs
index 89806f95..68b008ab 100644
--- a/egui_plot/src/items/mod.rs
+++ b/egui_plot/src/items/mod.rs
@@ -35,6 +35,7 @@ pub struct PlotItemBase {
     id: Id,
     highlight: bool,
     allow_hover: bool,
+    is_overlay: bool,
 }
 
 impl PlotItemBase {
@@ -45,6 +46,7 @@ impl PlotItemBase {
             id,
             highlight: false,
             allow_hover: true,
+            is_overlay: false,
         }
     }
 }
@@ -90,6 +92,14 @@ macro_rules! builder_methods_for_base {
             self.base_mut().id = id.into();
             self
         }
+
+        /// Places this element in the overlay layer, exempting it from automatic bounds calculation.
+        /// Default: `false`.
+        #[inline]
+        pub fn overlay(mut self, is_overlay: bool) -> Self {
+            self.base_mut().is_overlay = is_overlay;
+            self
+        }
     };
 }
 
@@ -198,6 +208,7 @@ pub trait PlotItem {
             label_formatter,
         );
     }
+    fn is_overlay(&self) -> bool;
 }
 
 // ----------------------------------------------------------------------------
@@ -298,6 +309,10 @@ impl PlotItem for HLine {
         bounds.max[1] = self.y;
         bounds
     }
+
+    fn is_overlay(&self) -> bool {
+        self.base().is_overlay
+    }
 }
 
 /// A vertical line in a plot, filling the full width
@@ -396,6 +411,10 @@ impl PlotItem for VLine {
         bounds.max[0] = self.x;
         bounds
     }
+
+    fn is_overlay(&self) -> bool {
+        self.base().is_overlay
+    }
 }
 
 /// A series of values forming a path.
@@ -424,6 +443,9 @@ impl<'a> Line<'a> {
         }
     }
 
+    /// Places this element in the overlay layer, exempting it from automatic bounds calculation.
+    /// Default: `false`.
+
     /// Add a stroke.
     #[inline]
     pub fn stroke(mut self, stroke: impl Into<Stroke>) -> Self {
@@ -609,6 +631,10 @@ impl PlotItem for Line<'_> {
     fn bounds(&self) -> PlotBounds {
         self.series.bounds()
     }
+
+    fn is_overlay(&self) -> bool {
+        self.base().is_overlay
+    }
 }
 
 /// A convex polygon.
@@ -719,6 +745,10 @@ impl PlotItem for Polygon<'_> {
     fn base_mut(&mut self) -> &mut PlotItemBase {
         &mut self.base
     }
+
+    fn is_overlay(&self) -> bool {
+        self.base().is_overlay
+    }
 }
 
 /// Text inside the plot.
@@ -812,6 +842,10 @@ impl PlotItem for Text {
     fn base_mut(&mut self) -> &mut PlotItemBase {
         &mut self.base
     }
+
+    fn is_overlay(&self) -> bool {
+        self.base().is_overlay
+    }
 }
 
 /// A set of points.
@@ -1039,6 +1073,10 @@ impl PlotItem for Points<'_> {
     fn base_mut(&mut self) -> &mut PlotItemBase {
         &mut self.base
     }
+
+    fn is_overlay(&self) -> bool {
+        self.base().is_overlay
+    }
 }
 
 /// A set of arrows.
@@ -1150,6 +1188,10 @@ impl PlotItem for Arrows<'_> {
     fn base_mut(&mut self) -> &mut PlotItemBase {
         &mut self.base
     }
+
+    fn is_overlay(&self) -> bool {
+        self.base().is_overlay
+    }
 }
 
 /// An image in the plot.
@@ -1307,6 +1349,10 @@ impl PlotItem for PlotImage {
     fn base_mut(&mut self) -> &mut PlotItemBase {
         &mut self.base
     }
+
+    fn is_overlay(&self) -> bool {
+        self.base().is_overlay
+    }
 }
 
 // ----------------------------------------------------------------------------
@@ -1468,6 +1514,10 @@ impl PlotItem for BarChart {
     fn base_mut(&mut self) -> &mut PlotItemBase {
         &mut self.base
     }
+
+    fn is_overlay(&self) -> bool {
+        self.base().is_overlay
+    }
 }
 
 /// A diagram containing a series of [`BoxElem`] elements.
@@ -1595,6 +1645,10 @@ impl PlotItem for BoxPlot {
     fn base_mut(&mut self) -> &mut PlotItemBase {
         &mut self.base
     }
+
+    fn is_overlay(&self) -> bool {
+        self.base().is_overlay
+    }
 }
 
 // ----------------------------------------------------------------------------
diff --git a/egui_plot/src/lib.rs b/egui_plot/src/lib.rs
index 506453f3..658e2fc8 100644
--- a/egui_plot/src/lib.rs
+++ b/egui_plot/src/lib.rs
@@ -1102,6 +1102,9 @@ impl<'a> Plot<'a> {
         // Set bounds automatically based on content.
         if auto_x || auto_y {
             for item in &items {
+                if item.is_overlay() {
+                    continue;
+                }
                 let item_bounds = item.bounds();
                 if auto_x {
                     bounds.merge_x(&item_bounds);