Add UiBuilder::layer_id

crates/egui/src/ui.rs

@@ -247,6 +247,7 @@ impl Ui {
         let UiBuilder {
             id_salt,
             ui_stack_info,
+            layer_id,
             max_rect,
             layout,
             disabled,
@@ -262,6 +263,9 @@ impl Ui {
         let max_rect = max_rect.unwrap_or_else(|| self.available_rect_before_wrap());
         let mut layout = layout.unwrap_or(*self.layout());
         let enabled = self.enabled && !disabled && !invisible;
+        if let Some(layer_id) = layer_id {
+            painter.set_layer_id(layer_id);
+        }
         if invisible {
             painter.set_invisible();
         }
@@ -2311,10 +2315,7 @@ impl Ui {
         layer_id: LayerId,
         add_contents: impl FnOnce(&mut Self) -> R,
     ) -> InnerResponse<R> {
-        self.scope(|ui| {
-            ui.painter.set_layer_id(layer_id);
-            add_contents(ui)
-        })
+        self.scope_builder(UiBuilder::new().layer_id(layer_id), add_contents)
     }
 
     /// A [`CollapsingHeader`] that starts out collapsed.

crates/egui/src/ui_builder.rs

@@ -1,6 +1,6 @@
 use std::{hash::Hash, sync::Arc};
 
-use crate::{Id, Layout, Rect, Sense, Style, UiStackInfo};
+use crate::{Id, LayerId, Layout, Rect, Sense, Style, UiStackInfo};
 
 #[allow(unused_imports)] // Used for doclinks
 use crate::Ui;
@@ -15,6 +15,7 @@ use crate::Ui;
 pub struct UiBuilder {
     pub id_salt: Option<Id>,
     pub ui_stack_info: UiStackInfo,
+    pub layer_id: Option<LayerId>,
     pub max_rect: Option<Rect>,
     pub layout: Option<Layout>,
     pub disabled: bool,
@@ -48,6 +49,13 @@ impl UiBuilder {
         self
     }
 
+    /// Show the [`Ui`] in a different [`LayerId`] from its parent.
+    #[inline]
+    pub fn layer_id(mut self, layer_id: LayerId) -> Self {
+        self.layer_id = Some(layer_id);
+        self
+    }
+
     /// Set the max rectangle, within which widgets will go.
     ///
     /// New widgets will *try* to fit within this rectangle.