Reconciliation (allowing state-preserving hot-reload)

Cargo.toml

@@ -2835,6 +2835,10 @@ wasm = false
 name = "bsn"
 path = "examples/scene/bsn.rs"
 
+[[example]]
+name = "bsn_reconcile"
+path = "examples/scene/bsn_reconcile.rs"
+
 [[example]]
 name = "ui_scene"
 path = "examples/scene/ui_scene.rs"

crates/bevy_ecs/src/template.rs

@@ -3,7 +3,7 @@
 pub use bevy_ecs_macros::GetTemplate;
 
 use crate::{
-    bundle::Bundle,
+    bundle::{Bundle, BundleInfo},
     entity::{Entity, EntityPath},
     error::{BevyError, Result},
     resource::Resource,
@@ -31,20 +31,20 @@ pub trait Template {
 
 /// The context used to apply the current [`Template`]. This contains a reference to the entity that the template is being
 /// applied to.
-pub struct TemplateContext<'a> {
+pub struct TemplateContext<'w, 'a> {
     /// The current entity the template is being applied to
-    pub entity: &'a mut EntityWorldMut<'a>,
+    pub entity: &'a mut EntityWorldMut<'w>,
     /// The scoped entities mapping for the current template context
     pub scoped_entities: &'a mut ScopedEntities,
     /// The entity scopes for the current template context. This matches
     /// the `scoped_entities`.
     pub entity_scopes: &'a EntityScopes,
 }
 
-impl<'a> TemplateContext<'a> {
+impl<'w, 'a> TemplateContext<'w, 'a> {
     /// Creates a new [`TemplateContext`].
     pub fn new(
-        entity: &'a mut EntityWorldMut<'a>,
+        entity: &'a mut EntityWorldMut<'w>,
         scoped_entities: &'a mut ScopedEntities,
         entity_scopes: &'a EntityScopes,
     ) -> Self {
@@ -127,7 +127,7 @@ impl EntityScopes {
 pub struct ScopedEntities(Vec<Option<Entity>>);
 
 impl ScopedEntities {
-    /// Creates a new [`ScopedEntities`] with the given `size`, intialized to [`None`] (no [`Entity`] assigned).  
+    /// Creates a new [`ScopedEntities`] with the given `size`, intialized to [`None`] (no [`Entity`] assigned).
     pub fn new(size: usize) -> Self {
         Self(vec![None; size])
     }
@@ -160,7 +160,7 @@ impl ScopedEntities {
     }
 }
 
-impl<'a> TemplateContext<'a> {
+impl<'w, 'a> TemplateContext<'w, 'a> {
     /// Retrieves a reference to the given resource `R`.
     pub fn resource<R: Resource>(&self) -> &R {
         self.entity.resource()
@@ -265,6 +265,13 @@ impl GetTemplate for Entity {
 pub trait ErasedTemplate: Downcast + Send + Sync {
     /// Applies this template to the given `entity`.
     fn apply(&mut self, context: &mut TemplateContext) -> Result<(), BevyError>;
+
+    /// Registers the output bundle of this template with the given `world`.
+    ///
+    /// Returns the [`BundleInfo`] of the registered bundle, or `None` if the template does not output a bundle.
+    fn register_bundle<'a>(&self, _: &'a mut World) -> Option<&'a BundleInfo> {
+        None
+    }
 }
 
 impl_downcast!(ErasedTemplate);
@@ -275,6 +282,10 @@ impl<T: Template<Output: Bundle> + Send + Sync + 'static> ErasedTemplate for T {
         context.entity.insert(bundle);
         Ok(())
     }
+
+    fn register_bundle<'a>(&self, world: &'a mut World) -> Option<&'a BundleInfo> {
+        Some(world.register_bundle::<T::Output>())
+    }
 }
 
 // TODO: Consider cutting this

crates/bevy_feathers/src/controls/button.rs

@@ -28,6 +28,11 @@ use bevy_input_focus::tab_navigation::TabIndex;
 /// system to identify which entities are buttons.
 #[derive(Component, Default, Clone, Reflect, Debug, PartialEq, Eq)]
 #[reflect(Component, Clone, Default)]
+#[require(
+    Hovered,
+    ThemeBackgroundColor(tokens::BUTTON_BG),
+    ThemeFontColor(tokens::BUTTON_TEXT)
+)]
 pub enum ButtonVariant {
     /// The standard button appearance
     #[default]
@@ -61,11 +66,8 @@ pub fn button(props: ButtonProps) -> impl Scene {
             flex_grow: 1.0,
         }
         Button
-        Hovered
         EntityCursor::System(bevy_window::SystemCursorIcon::Pointer)
         TabIndex(0)
-        ThemeBackgroundColor(tokens::BUTTON_BG)
-        ThemeFontColor(tokens::BUTTON_TEXT)
         template_value(props.variant)
         template_value(props.corners.to_border_radius(4.0))
         InheritableFont {
@@ -89,11 +91,8 @@ pub fn tool_button(props: ButtonProps) -> impl Scene {
             flex_grow: 1.0,
         }
         Button
-        Hovered
         EntityCursor::System(bevy_window::SystemCursorIcon::Pointer)
         TabIndex(0)
-        ThemeBackgroundColor(tokens::BUTTON_BG)
-        ThemeFontColor(tokens::BUTTON_TEXT)
         InheritableFont {
             font: fonts::REGULAR,
             font_size: 14.0,

crates/bevy_feathers/src/controls/checkbox.rs

@@ -32,16 +32,22 @@ use crate::{
 /// Marker for the checkbox frame (contains both checkbox and label)
 #[derive(Component, Default, Clone, Reflect)]
 #[reflect(Component, Clone, Default)]
+#[require(Hovered, ThemeFontColor(tokens::CHECKBOX_TEXT))]
 struct CheckboxFrame;
 
 /// Marker for the checkbox outline
 #[derive(Component, Default, Clone, Reflect)]
 #[reflect(Component, Clone, Default)]
+#[require(
+    ThemeBackgroundColor(tokens::CHECKBOX_BG),
+    ThemeBorderColor(tokens::CHECKBOX_BORDER)
+)]
 struct CheckboxOutline;
 
 /// Marker for the checkbox check mark
 #[derive(Component, Default, Clone, Reflect)]
 #[reflect(Component, Clone, Default)]
+#[require(ThemeBorderColor(tokens::CHECKBOX_MARK))]
 struct CheckboxMark;
 
 /// Checkbox scene function.
@@ -59,10 +65,8 @@ pub fn checkbox() -> impl Scene {
         }
         Checkbox
         CheckboxFrame
-        Hovered
         EntityCursor::System(bevy_window::SystemCursorIcon::Pointer)
         TabIndex(0)
-        ThemeFontColor(tokens::CHECKBOX_TEXT)
         InheritableFont {
             font: fonts::REGULAR,
             font_size: 14.0,
@@ -75,8 +79,6 @@ pub fn checkbox() -> impl Scene {
             }
             CheckboxOutline
             BorderRadius::all(Val::Px(4.0))
-            ThemeBackgroundColor(tokens::CHECKBOX_BG)
-            ThemeBorderColor(tokens::CHECKBOX_BORDER)
             [(
                 // Cheesy checkmark: rotated node with L-shaped border.
                 Node {
@@ -92,7 +94,6 @@ pub fn checkbox() -> impl Scene {
                 }
                 UiTransform::from_rotation(Rot2::FRAC_PI_4)
                 CheckboxMark
-                ThemeBorderColor(tokens::CHECKBOX_MARK)
             )]
         )]
     }

crates/bevy_feathers/src/controls/color_slider.rs

@@ -167,8 +167,38 @@ pub struct ColorSlider {
 #[derive(Component, Default, Clone)]
 struct ColorSliderTrack;
 
+/// Marker for the left/right endcaps
+#[derive(Component, Default, Clone)]
+#[require(BackgroundColor)]
+struct ColorSliderEndCap;
+
+#[derive(Component, Default, Clone)]
+#[require(
+    BackgroundGradient(vec![Gradient::Linear(LinearGradient {
+        angle: PI * 0.5,
+        stops: vec![
+            ColorStop::new(Color::NONE, Val::Percent(0.)),
+            ColorStop::new(Color::NONE, Val::Percent(50.)),
+            ColorStop::new(Color::NONE, Val::Percent(100.)),
+        ],
+        color_space: InterpolationColorSpace::Srgba,
+    })])
+)]
+struct ColorSliderGradient;
+
 /// Marker for the thumb
 #[derive(Component, Default, Clone)]
+#[require(
+    Node {
+        position_type: PositionType::Absolute,
+        left: Val::Percent(0.),
+        top: Val::Percent(50.),
+        width: Val::Px(THUMB_SIZE),
+        height: Val::Px(THUMB_SIZE),
+        border: UiRect::all(Val::Px(2.0)),
+        ..Default::default()
+    }
+)]
 struct ColorSliderThumb;
 
 /// Spawn a new slider widget.
@@ -213,36 +243,20 @@ pub fn color_slider(props: ColorSliderProps) -> impl Scene {
                 [
                     // Left endcap
                     (
+                        ColorSliderEndCap
                         Node {
                             width: Val::Px({THUMB_SIZE * 0.5}),
                         }
                         template_value(RoundedCorners::Left.to_border_radius(TRACK_RADIUS))
-                        BackgroundColor({palette::X_AXIS})
                     ),
                     // Track with gradient
                     (
+                        ColorSliderGradient
                         Node {
                             flex_grow: 1.0,
                         }
-                        BackgroundGradient({vec![Gradient::Linear(LinearGradient {
-                            angle: PI * 0.5,
-                            stops: vec![
-                                ColorStop::new(Color::NONE, Val::Percent(0.)),
-                                ColorStop::new(Color::NONE, Val::Percent(50.)),
-                                ColorStop::new(Color::NONE, Val::Percent(100.)),
-                            ],
-                            color_space: InterpolationColorSpace::Srgba,
-                        })]})
                         ZIndex(1)
                         [(
-                            Node {
-                                position_type: PositionType::Absolute,
-                                left: Val::Percent(0.),
-                                top: Val::Percent(50.),
-                                width: Val::Px(THUMB_SIZE),
-                                height: Val::Px(THUMB_SIZE),
-                                border: UiRect::all(Val::Px(2.0)),
-                            }
                             SliderThumb
                             ColorSliderThumb
                             BorderRadius::MAX
@@ -260,11 +274,11 @@ pub fn color_slider(props: ColorSliderProps) -> impl Scene {
                     ),
                     // Right endcap
                     (
+                        ColorSliderEndCap
                         Node {
                             width: Val::Px({THUMB_SIZE * 0.5}),
                         }
                         template_value(RoundedCorners::Right.to_border_radius(TRACK_RADIUS))
-                        BackgroundColor({palette::Z_AXIS})
                     ),
                 ]
             )

crates/bevy_feathers/src/controls/radio.rs

@@ -31,13 +31,21 @@ use bevy_scene2::prelude::*;
 /// Marker for the radio outline
 #[derive(Component, Default, Clone, Reflect)]
 #[reflect(Component, Clone, Default)]
+#[require(ThemeBorderColor(tokens::RADIO_BORDER))]
 struct RadioOutline;
 
 /// Marker for the radio check mark
 #[derive(Component, Default, Clone, Reflect)]
 #[reflect(Component, Clone, Default)]
+#[require(ThemeBackgroundColor(tokens::RADIO_MARK))]
 struct RadioMark;
 
+/// Marker for the radio frame
+#[derive(Component, Default, Clone, Reflect)]
+#[reflect(Component, Clone, Default)]
+#[require(Hovered, ThemeFontColor(tokens::RADIO_TEXT))]
+pub struct RadioFrame;
+
 /// Radio scene function.
 pub fn radio() -> impl Scene {
     bsn! {
@@ -49,10 +57,9 @@ pub fn radio() -> impl Scene {
             column_gap: Val::Px(4.0),
         }
         RadioButton
-        Hovered
+        RadioFrame
         EntityCursor::System(bevy_window::SystemCursorIcon::Pointer)
         TabIndex(0)
-        ThemeFontColor(tokens::RADIO_TEXT)
         InheritableFont {
             font: fonts::REGULAR,
             font_size: 14.0,
@@ -68,7 +75,6 @@ pub fn radio() -> impl Scene {
             }
             RadioOutline
             BorderRadius::MAX
-            ThemeBorderColor(tokens::RADIO_BORDER)
             [(
                 // Cheesy checkmark: rotated node with L-shaped border.
                 Node {
@@ -77,7 +83,6 @@ pub fn radio() -> impl Scene {
                 }
                 BorderRadius::MAX
                 RadioMark
-                ThemeBackgroundColor(tokens::RADIO_MARK)
             )]
         )]
     }

crates/bevy_feathers/src/controls/slider.rs

@@ -34,8 +34,6 @@ use crate::{
 
 /// Slider template properties, passed to [`slider`] function.
 pub struct SliderProps {
-    /// Slider current value
-    pub value: f32,
     /// Slider minimum value
     pub min: f32,
     /// Slider maximum value
@@ -44,22 +42,31 @@ pub struct SliderProps {
 
 impl Default for SliderProps {
     fn default() -> Self {
-        Self {
-            value: 0.0,
-            min: 0.0,
-            max: 1.0,
-        }
+        Self { min: 0.0, max: 1.0 }
     }
 }
 
 #[derive(Component, Default, Clone, Reflect)]
-#[require(Slider)]
 #[reflect(Component, Clone, Default)]
+#[require(
+    SliderValue,
+    BackgroundGradient(vec![Gradient::Linear(LinearGradient {
+        angle: PI * 0.5,
+        stops: vec![
+            ColorStop::new(Color::NONE, Val::Percent(0.)),
+            ColorStop::new(Color::NONE, Val::Percent(50.)),
+            ColorStop::new(Color::NONE, Val::Percent(50.)),
+            ColorStop::new(Color::NONE, Val::Percent(100.)),
+        ],
+        color_space: InterpolationColorSpace::Srgba,
+    })])
+)]
 struct SliderStyle;
 
 /// Marker for the text
 #[derive(Component, Default, Clone, Reflect)]
 #[reflect(Component, Clone, Default)]
+#[require(Text)]
 struct SliderValueText;
 
 /// Slider scene function.
@@ -80,22 +87,10 @@ pub fn slider(props: SliderProps) -> impl Scene {
             track_click: TrackClick::Drag,
         }
         SliderStyle
-        SliderValue({props.value})
         SliderRange::new(props.min, props.max)
         EntityCursor::System(bevy_window::SystemCursorIcon::EwResize)
         TabIndex(0)
         template_value(RoundedCorners::All.to_border_radius(6.0))
-        // Use a gradient to draw the moving bar
-        BackgroundGradient({vec![Gradient::Linear(LinearGradient {
-            angle: PI * 0.5,
-            stops: vec![
-                ColorStop::new(Color::NONE, Val::Percent(0.)),
-                ColorStop::new(Color::NONE, Val::Percent(50.)),
-                ColorStop::new(Color::NONE, Val::Percent(50.)),
-                ColorStop::new(Color::NONE, Val::Percent(100.)),
-            ],
-            color_space: InterpolationColorSpace::Srgba,
-        })]})
         [(
             // Text container
             Node {
@@ -110,7 +105,7 @@ pub fn slider(props: SliderProps) -> impl Scene {
                 font: fonts::MONO,
                 font_size: 12.0,
             }
-            [(Text::new("10.0") ThemedText SliderValueText)]
+            [(ThemedText SliderValueText)]
         )]
     }
 }