Renaming, comment & better default system

crates/egui/src/context.rs

@@ -38,7 +38,7 @@ use crate::{
     resize, response, scroll_area, theme_plugin,
     util::IdTypeMap,
     viewport::ViewportClass,
-    widget_style::{Classes, StyleStruct, WidgetState},
+    widget_style::{Classes, WidgetState, WidgetStyle},
 };
 
 use crate::IdMap;
@@ -2031,37 +2031,36 @@ impl Context {
 }
 
 impl Context {
-    /// Register a [`ThemeStyle`](crate::theme_plugin::ThemeStyle) for the specified widget [`StyleStruct`](StyleStruct) `S`
+    /// Register a [`ThemeStyle`](crate::theme_plugin::ThemeStyle) for the specified widget type.
     ///
     /// A theme can only be added once for a specified widget.
-    /// This way it's convenient to add themes in `eframe::run_simple_native`.
-    /// If you want to add the theme anyway, use [`Self::replace_theme`] instead.
-    pub fn add_theme<S: StyleStruct + 'static>(
+    /// If a theme is already registered for this widget, this is a no-op (useful for `eframe::run_simple_native`).
+    ///
+    /// If you want to add the theme anyway, use [`Self::replace_widget_theme`] instead.
+    pub fn add_widget_theme<S: WidgetStyle + 'static>(
         &self,
         theme: impl theme_plugin::ThemeStyle<S> + Send + Sync + 'static,
     ) {
         self.write(|ctx| ctx.themes.register::<S>(theme, false));
     }
 
-    /// Register a [`ThemeStyle`](crate::theme_plugin::ThemeStyle) for the specified widget [`StyleStruct`](StyleStruct) `S`
+    /// Register a [`ThemeStyle`](crate::theme_plugin::ThemeStyle) for the specified widget.
     ///
-    /// Overwrite any theme already registered for the specified widget [`StyleStruct`](StyleStruct).
-    /// If you want to avoid overwriting existing theme, use [`Self::add_theme`] instead.
-    pub fn replace_theme<S: StyleStruct + 'static>(
+    /// Overwrite any theme already registered for the specified widget [`WidgetStyle`](WidgetStyle).
+    /// This allow to live edit a theme.
+    pub fn replace_widget_theme<S: WidgetStyle + 'static>(
         &self,
         theme: impl theme_plugin::ThemeStyle<S> + Send + Sync + 'static,
     ) {
         self.write(|ctx| ctx.themes.register::<S>(theme, true));
     }
 
-    /// Compute the [`StyleStruct`] using the registered theme if available.
-    ///
-    /// Return `None` if no theme was registered for the [`StyleStruct`]
-    pub fn get_style<S: StyleStruct + Clone + 'static>(
+    /// Compute the [`WidgetStyle`] using the registered theme.
+    pub(crate) fn get_widget_style<S: WidgetStyle + Clone + 'static>(
         &self,
         classes: &Classes,
         state: WidgetState,
-    ) -> Option<S> {
+    ) -> S {
         self.write(move |ctx| ctx.themes.get::<S>(classes, state))
     }
 }

crates/egui/src/theme_plugin.rs

@@ -1,11 +1,16 @@
-use std::sync::Arc;
+use std::{any::TypeId, sync::Arc};
 
-use epaint::mutex::Mutex;
+use emath::Vec2;
+use epaint::{Shadow, Stroke, mutex::Mutex, text::TextWrapMode};
 
 use crate::{
-    Id, Ui,
+    Frame, Id, Spacing, Style, TextStyle, Ui, Visuals,
+    style::Widgets,
     util::IdTypeMap,
-    widget_style::{Classes, StyleStruct, WidgetState},
+    widget_style::{
+        BaseStyle, ButtonStyle, CheckboxStyle, Classes, HasClasses as _, LabelStyle,
+        SELECTED_CLASS, SeparatorStyle, TextVisuals, WidgetState, WidgetStyle,
+    },
 };
 
 /// A cache that can be implemented to reduce computation time of a `ThemeStyle`
@@ -15,12 +20,12 @@ pub struct ThemeCache {
 }
 
 impl ThemeCache {
-    /// Access the cache for the requested [`StyleStruct`] based on the [`Classes`] and
+    /// Access the cache for the requested [`WidgetStyle`] based on the [`Classes`] and
     /// the [`WidgetState`]
     ///
     /// If no entry match the parameter then compute the fallback style and
     /// save the output for later.
-    pub fn get<S: StyleStruct + 'static>(
+    pub fn get<S: WidgetStyle + 'static>(
         &mut self,
         classes: &Classes,
         state: WidgetState,
@@ -37,45 +42,201 @@ impl ThemeCache {
     }
 }
 
-/// A Theme plugin that implement a style computation for a defined `StyleStruct`
+/// A Theme plugin that implement a style computation for a defined `WidgetStyle`
 pub trait ThemeStyle<S> {
     /// The style according to the classes and state of the widget
-    fn style(&mut self, classes: &Classes, state: WidgetState) -> S;
+    fn style(&mut self, themes: &Themes, classes: &Classes, state: WidgetState) -> S;
+
+    /// Help to differ the different themes
+    fn theme_type_id(&self) -> TypeId
+    where
+        Self: 'static,
+    {
+        TypeId::of::<Self>()
+    }
+}
+
+#[derive(Debug, Clone)]
+struct DefaultStyle;
+
+impl ThemeStyle<BaseStyle> for DefaultStyle {
+    fn style(&mut self, _themes: &Themes, _classes: &Classes, state: WidgetState) -> BaseStyle {
+        let visuals = Widgets::dark();
+        let spacing = Spacing::default();
+
+        let visuals = match state {
+            WidgetState::Noninteractive => visuals.noninteractive,
+            WidgetState::Inactive => visuals.inactive,
+            WidgetState::Hovered => visuals.hovered,
+            WidgetState::Active => visuals.active,
+        };
+
+        BaseStyle {
+            frame: Frame {
+                fill: visuals.bg_fill,
+                stroke: visuals.bg_stroke,
+                corner_radius: visuals.corner_radius,
+                inner_margin: spacing.button_padding.into(),
+                ..Default::default()
+            },
+            stroke: visuals.fg_stroke,
+            text: TextVisuals {
+                color: visuals.text_color(),
+                font_id: TextStyle::Body.resolve(&Style::default()),
+                strikethrough: Stroke::NONE,
+                underline: Stroke::NONE,
+            },
+        }
+    }
+}
+
+impl ThemeStyle<ButtonStyle> for DefaultStyle {
+    fn style(&mut self, themes: &Themes, classes: &Classes, state: WidgetState) -> ButtonStyle {
+        let widget_visuals = Widgets::dark();
+        let spacing = Spacing::default();
+
+        let mut widget_visuals = match state {
+            WidgetState::Noninteractive => widget_visuals.noninteractive,
+            WidgetState::Inactive => widget_visuals.inactive,
+            WidgetState::Hovered => widget_visuals.hovered,
+            WidgetState::Active => widget_visuals.active,
+        };
+
+        let mut ws: BaseStyle = themes.get(classes, state);
+
+        if classes.has(SELECTED_CLASS) {
+            let visuals = Visuals::default();
+            widget_visuals.weak_bg_fill = visuals.selection.bg_fill;
+            widget_visuals.bg_fill = visuals.selection.bg_fill;
+            widget_visuals.fg_stroke = visuals.selection.stroke;
+            ws.text.color = visuals.selection.stroke.color;
+        }
+
+        ButtonStyle {
+            frame: Frame {
+                fill: widget_visuals.weak_bg_fill,
+                stroke: widget_visuals.bg_stroke,
+                corner_radius: widget_visuals.corner_radius,
+                outer_margin: (-Vec2::splat(widget_visuals.expansion)).into(),
+                inner_margin: (spacing.button_padding + Vec2::splat(widget_visuals.expansion)
+                    - Vec2::splat(widget_visuals.bg_stroke.width))
+                .into(),
+                ..Default::default()
+            },
+            text_style: ws.text,
+        }
+    }
+}
+
+impl ThemeStyle<CheckboxStyle> for DefaultStyle {
+    fn style(&mut self, themes: &Themes, classes: &Classes, state: WidgetState) -> CheckboxStyle {
+        let widget_visuals = Widgets::dark();
+        let spacing = Spacing::default();
+
+        let widget_visuals = match state {
+            WidgetState::Noninteractive => widget_visuals.noninteractive,
+            WidgetState::Inactive => widget_visuals.inactive,
+            WidgetState::Hovered => widget_visuals.hovered,
+            WidgetState::Active => widget_visuals.active,
+        };
+
+        let ws: BaseStyle = themes.get(classes, state);
+
+        CheckboxStyle {
+            frame: Frame::new(),
+            checkbox_size: spacing.icon_width,
+            check_size: spacing.icon_width_inner,
+            checkbox_frame: Frame {
+                fill: widget_visuals.bg_fill,
+                corner_radius: widget_visuals.corner_radius,
+                stroke: widget_visuals.bg_stroke,
+                ..Default::default()
+            },
+            text_style: ws.text,
+            check_stroke: ws.stroke,
+        }
+    }
+}
+
+impl ThemeStyle<LabelStyle> for DefaultStyle {
+    fn style(&mut self, themes: &Themes, classes: &Classes, state: WidgetState) -> LabelStyle {
+        let ws: BaseStyle = themes.get(classes, state);
+
+        LabelStyle {
+            frame: Frame {
+                fill: ws.frame.fill,
+                inner_margin: 0.0.into(),
+                outer_margin: 0.0.into(),
+                stroke: Stroke::NONE,
+                shadow: Shadow::NONE,
+                corner_radius: 0.into(),
+            },
+            text: ws.text,
+            wrap_mode: TextWrapMode::Wrap,
+        }
+    }
+}
+
+impl ThemeStyle<SeparatorStyle> for DefaultStyle {
+    fn style(&mut self, themes: &Themes, classes: &Classes, state: WidgetState) -> SeparatorStyle {
+        let ws: BaseStyle = themes.get(classes, state);
+
+        SeparatorStyle {
+            spacing: 6.0,
+            stroke: ws.frame.stroke,
+        }
+    }
 }
 
 impl Ui {
-    /// Access the installed theme plugin if there is one and fetch the requested widget style if it exist.
-    /// Fallback to the default style if not found.
+    /// Access the register theme and fetch the requested [`WidgetStyle`].
     ///
-    /// Requested widget style must implement [`StyleStruct`].
-    pub fn widget_style<S: StyleStruct + Clone + 'static>(
+    /// Requested widget style must implement [`WidgetStyle`].
+    pub fn widget_style<S: WidgetStyle + Clone + 'static>(
         &self,
         id: crate::Id,
         classes: &Classes,
     ) -> S {
         // Fetch the current state of the widget
         let state = self
-            .ctx()
             .read_response(id)
             .map(|r| r.widget_state())
             .unwrap_or_default();
 
-        if let Some(style) = self.get_style::<S>(classes, state) {
-            style
-        } else {
-            S::default_style(classes, state)
-        }
+        self.get_widget_style::<S>(classes, state)
     }
 }
 
-#[derive(Default)]
-pub(crate) struct Themes {
+pub struct Themes {
     themes: IdTypeMap,
 }
 
+type ThemeWrap<S> = Arc<Mutex<Box<dyn ThemeStyle<S> + Send + Sync>>>;
+
+impl Default for Themes {
+    /// Register the default egui theme
+    fn default() -> Self {
+        let mut themes = IdTypeMap::default();
+
+        themes.insert_temp::<ThemeWrap<BaseStyle>>(
+            Id::NULL,
+            Arc::new(Mutex::new(Box::new(DefaultStyle))),
+        );
+
+        themes.insert_temp::<ThemeWrap<ButtonStyle>>(
+            Id::NULL,
+            Arc::new(Mutex::new(Box::new(DefaultStyle))),
+        );
+
+        Self { themes }
+    }
+}
+
 impl Themes {
-    /// Register a theme and the style associated
-    pub(crate) fn register<S: StyleStruct + 'static>(
+    /// Register a [`ThemeStyle`](crate::theme_plugin::ThemeStyle) for the specified widget [`WidgetStyle`](WidgetStyle) `S`
+    ///
+    /// Existing themes are overwritten if `force` is `true` or the new theme differs.
+    pub(crate) fn register<S: WidgetStyle + 'static>(
         &mut self,
         theme: impl ThemeStyle<S> + Send + Sync + 'static,
         force: bool,
@@ -84,10 +245,11 @@ impl Themes {
             && self
                 .themes
                 .get_temp::<Arc<Mutex<Box<dyn ThemeStyle<S> + Send + Sync>>>>(Id::NULL)
-                .is_some()
+                .is_some_and(|t| t.lock().theme_type_id() == theme.theme_type_id())
         {
             return;
         }
+
         self.themes
             .insert_temp::<Arc<Mutex<Box<dyn ThemeStyle<S> + Send + Sync>>>>(
                 Id::NULL,
@@ -96,14 +258,13 @@ impl Themes {
     }
 
     /// Fetch the style of the current theme
-    pub(crate) fn get<S: StyleStruct + 'static>(
-        &self,
-        classes: &Classes,
-        state: WidgetState,
-    ) -> Option<S> {
+    pub fn get<S: WidgetStyle + 'static>(&self, classes: &Classes, state: WidgetState) -> S {
         let v = self
             .themes
             .get_temp::<Arc<Mutex<Box<dyn ThemeStyle<S> + Send + Sync>>>>(Id::NULL);
-        v.map(|engine| engine.lock().style(classes, state))
+
+        v.unwrap_or_else(|| panic!("A style should be set for {:?}", std::any::type_name::<S>()))
+            .lock()
+            .style(self, classes, state)
     }
 }

crates/egui/src/widget_style.rs

@@ -3,22 +3,16 @@ use std::{
     fmt::{self, Debug},
 };
 
-use emath::Vec2;
-use epaint::{Color32, FontId, Shadow, Stroke, text::TextWrapMode};
+use epaint::{Color32, FontId, Stroke, text::TextWrapMode};
 use smallvec::SmallVec;
 
 use crate::{
-    Frame, Response, Spacing, Style, TextBuffer as _, TextStyle, Visuals,
+    Frame, Response, TextBuffer as _,
     style::{WidgetVisuals, Widgets},
 };
 
 /// Each dedicated style must implement this trait to be used in the theme plugin system
-pub trait StyleStruct: Debug + Clone + Send + Sync + std::any::Any + 'static {
-    /// The default style for this struct based on classes and state of the widget.
-    fn default_style(classes: &Classes, state: WidgetState) -> Self
-    where
-        Self: Sized;
-}
+pub trait WidgetStyle: Debug + Clone + Send + Sync + std::any::Any + 'static {}
 
 /// General text style
 #[derive(Debug, Clone)]
@@ -36,7 +30,7 @@ pub struct TextVisuals {
 
 /// General widget style
 #[derive(Debug, Clone)]
-pub struct WidgetStyle {
+pub struct BaseStyle {
     pub frame: Frame,
 
     pub text: TextVisuals,
@@ -44,36 +38,7 @@ pub struct WidgetStyle {
     pub stroke: Stroke,
 }
 
-impl StyleStruct for WidgetStyle {
-    fn default_style(_classes: &Classes, state: WidgetState) -> Self {
-        let visuals = Widgets::dark();
-        let spacing = Spacing::default();
-
-        let visuals = match state {
-            WidgetState::Noninteractive => visuals.noninteractive,
-            WidgetState::Inactive => visuals.inactive,
-            WidgetState::Hovered => visuals.hovered,
-            WidgetState::Active => visuals.active,
-        };
-
-        Self {
-            frame: Frame {
-                fill: visuals.bg_fill,
-                stroke: visuals.bg_stroke,
-                corner_radius: visuals.corner_radius,
-                inner_margin: spacing.button_padding.into(),
-                ..Default::default()
-            },
-            stroke: visuals.fg_stroke,
-            text: TextVisuals {
-                color: visuals.text_color(),
-                font_id: TextStyle::Button.resolve(&Style::default()),
-                strikethrough: Stroke::NONE,
-                underline: Stroke::NONE,
-            },
-        }
-    }
-}
+impl WidgetStyle for BaseStyle {}
 
 /// Dedicated button style
 #[derive(Debug, Clone)]
@@ -82,43 +47,7 @@ pub struct ButtonStyle {
     pub text_style: TextVisuals,
 }
 
-impl StyleStruct for ButtonStyle {
-    fn default_style(classes: &Classes, state: WidgetState) -> Self {
-        let widget_visuals = Widgets::dark();
-        let spacing = Spacing::default();
-
-        let mut widget_visuals = match state {
-            WidgetState::Noninteractive => widget_visuals.noninteractive,
-            WidgetState::Inactive => widget_visuals.inactive,
-            WidgetState::Hovered => widget_visuals.hovered,
-            WidgetState::Active => widget_visuals.active,
-        };
-
-        let mut ws = WidgetStyle::default_style(classes, state);
-
-        if classes.has(SELECTED_CLASS) {
-            let visuals = Visuals::default();
-            widget_visuals.weak_bg_fill = visuals.selection.bg_fill;
-            widget_visuals.bg_fill = visuals.selection.bg_fill;
-            widget_visuals.fg_stroke = visuals.selection.stroke;
-            ws.text.color = visuals.selection.stroke.color;
-        }
-
-        Self {
-            frame: Frame {
-                fill: widget_visuals.weak_bg_fill,
-                stroke: widget_visuals.bg_stroke,
-                corner_radius: widget_visuals.corner_radius,
-                outer_margin: (-Vec2::splat(widget_visuals.expansion)).into(),
-                inner_margin: (spacing.button_padding + Vec2::splat(widget_visuals.expansion)
-                    - Vec2::splat(widget_visuals.bg_stroke.width))
-                .into(),
-                ..Default::default()
-            },
-            text_style: ws.text,
-        }
-    }
-}
+impl WidgetStyle for ButtonStyle {}
 
 /// Dedicated checkbox style
 #[derive(Debug, Clone)]
@@ -142,35 +71,7 @@ pub struct CheckboxStyle {
     pub check_stroke: Stroke,
 }
 
-impl StyleStruct for CheckboxStyle {
-    fn default_style(classes: &Classes, state: WidgetState) -> Self {
-        let widget_visuals = Widgets::dark();
-        let spacing = Spacing::default();
-
-        let widget_visuals = match state {
-            WidgetState::Noninteractive => widget_visuals.noninteractive,
-            WidgetState::Inactive => widget_visuals.inactive,
-            WidgetState::Hovered => widget_visuals.hovered,
-            WidgetState::Active => widget_visuals.active,
-        };
-
-        let ws = WidgetStyle::default_style(classes, state);
-
-        Self {
-            frame: Frame::new(),
-            checkbox_size: spacing.icon_width,
-            check_size: spacing.icon_width_inner,
-            checkbox_frame: Frame {
-                fill: widget_visuals.bg_fill,
-                corner_radius: widget_visuals.corner_radius,
-                stroke: widget_visuals.bg_stroke,
-                ..Default::default()
-            },
-            text_style: ws.text,
-            check_stroke: ws.stroke,
-        }
-    }
-}
+impl WidgetStyle for CheckboxStyle {}
 
 /// Dedicated label style
 #[derive(Debug, Clone)]
@@ -185,6 +86,8 @@ pub struct LabelStyle {
     pub wrap_mode: TextWrapMode,
 }
 
+impl WidgetStyle for LabelStyle {}
+
 /// Dedicated separator style
 #[derive(Debug, Clone)]
 pub struct SeparatorStyle {
@@ -195,6 +98,8 @@ pub struct SeparatorStyle {
     pub stroke: Stroke,
 }
 
+impl WidgetStyle for SeparatorStyle {}
+
 /// The different state of a widget can be
 #[derive(Default, Clone, Copy, Debug, PartialEq, Eq, Hash)]
 pub enum WidgetState {
@@ -231,109 +136,6 @@ impl Response {
     }
 }
 
-impl Style {
-    /// The general widget style. The style is computed according to the classes and state of the widget.
-    pub fn widget_style(&self, _classes: &Classes, state: WidgetState) -> WidgetStyle {
-        let visuals = self.visuals.widgets.state(state);
-        let font_id = self.override_font_id.clone();
-        WidgetStyle {
-            frame: Frame {
-                fill: visuals.bg_fill,
-                stroke: visuals.bg_stroke,
-                corner_radius: visuals.corner_radius,
-                inner_margin: self.spacing.button_padding.into(),
-                ..Default::default()
-            },
-            stroke: visuals.fg_stroke,
-            text: TextVisuals {
-                color: self
-                    .visuals
-                    .override_text_color
-                    .unwrap_or_else(|| visuals.text_color()),
-                font_id: font_id.unwrap_or_else(|| TextStyle::Body.resolve(self)),
-                strikethrough: Stroke::NONE,
-                underline: Stroke::NONE,
-            },
-        }
-    }
-
-    /// The dedicated button style. The style is computed according to the classes and state of the widget.
-    /// It depend on the general widget style.
-    pub fn button_style(&self, classes: &Classes, state: WidgetState) -> ButtonStyle {
-        let mut visuals = *self.visuals.widgets.state(state);
-        let mut ws = self.widget_style(classes, state);
-
-        if classes.has(SELECTED_CLASS) {
-            visuals.weak_bg_fill = self.visuals.selection.bg_fill;
-            visuals.bg_fill = self.visuals.selection.bg_fill;
-            visuals.fg_stroke = self.visuals.selection.stroke;
-            ws.text.color = self.visuals.selection.stroke.color;
-        }
-
-        ButtonStyle {
-            frame: Frame {
-                fill: visuals.weak_bg_fill,
-                stroke: visuals.bg_stroke,
-                corner_radius: visuals.corner_radius,
-                outer_margin: (-Vec2::splat(visuals.expansion)).into(),
-                inner_margin: (self.spacing.button_padding + Vec2::splat(visuals.expansion)
-                    - Vec2::splat(visuals.bg_stroke.width))
-                .into(),
-                ..Default::default()
-            },
-            text_style: ws.text,
-        }
-    }
-
-    /// The dedicated checkbox style. The style is computed according to the classes and state of the widget.
-    /// It depend on the general widget style.
-    pub fn checkbox_style(&self, classes: &Classes, state: WidgetState) -> CheckboxStyle {
-        let visuals = self.visuals.widgets.state(state);
-        let ws = self.widget_style(classes, state);
-        CheckboxStyle {
-            frame: Frame::new(),
-            checkbox_size: self.spacing.icon_width,
-            check_size: self.spacing.icon_width_inner,
-            checkbox_frame: Frame {
-                fill: visuals.bg_fill,
-                corner_radius: visuals.corner_radius,
-                stroke: visuals.bg_stroke,
-                ..Default::default()
-            },
-            text_style: ws.text,
-            check_stroke: ws.stroke,
-        }
-    }
-
-    /// The dedicated label style. The style is computed according to the classes and state of the widget.
-    /// It depend on the general widget style.
-    pub fn label_style(&self, classes: &Classes, state: WidgetState) -> LabelStyle {
-        let ws = self.widget_style(classes, state);
-        LabelStyle {
-            frame: Frame {
-                fill: ws.frame.fill,
-                inner_margin: 0.0.into(),
-                outer_margin: 0.0.into(),
-                stroke: Stroke::NONE,
-                shadow: Shadow::NONE,
-                corner_radius: 0.into(),
-            },
-            text: ws.text,
-            wrap_mode: TextWrapMode::Wrap,
-        }
-    }
-
-    /// The dedicated separator style. The style is computed according to the classes and state of the widget.
-    /// It depend on the general widget style.
-    pub fn separator_style(&self, _classes: &Classes, _state: WidgetState) -> SeparatorStyle {
-        let visuals = self.visuals.noninteractive();
-        SeparatorStyle {
-            spacing: 6.0,
-            stroke: visuals.bg_stroke,
-        }
-    }
-}
-
 /// The root class is a special class present on every top-level [`crate::Ui`].
 pub const ROOT_CLASS: &str = "root";
 

crates/egui/src/widgets/button.rs

@@ -328,7 +328,6 @@ impl<'a> Button<'a> {
 
         classes.add_class_if(SELECTED_CLASS, selected.unwrap_or(false));
 
-        // let ButtonStyle { frame, text_style } = ui.style().button_style(&classes, state);
         let ButtonStyle { frame, text_style } = ui.widget_style(id, &classes);
 
         let mut button_padding = if has_frame_margin {

crates/egui/src/widgets/checkbox.rs

@@ -80,7 +80,7 @@ impl Widget for Checkbox<'_> {
             frame,
             check_stroke,
             text_style,
-        } = ui.style().checkbox_style(&classes, state);
+        } = ui.widget_style(id, &classes);
 
         let mut min_size = Vec2::splat(ui.spacing().interact_size.y);
         min_size.y = min_size.y.at_least(checkbox_size);

crates/egui/src/widgets/separator.rs

@@ -106,7 +106,7 @@ impl Widget for Separator {
         let SeparatorStyle {
             spacing: spacing_style,
             stroke,
-        } = ui.style().separator_style(&classes, state);
+        } = ui.widget_style(id, &classes);
 
         // override the spacing if not set
         let spacing = spacing.unwrap_or(spacing_style);

examples/styling_engine/src/custom_engine.rs

@@ -2,9 +2,9 @@ use std::collections::HashMap;
 
 use eframe::egui::{
     Color32,
-    theme_plugin::{ThemeCache, ThemeStyle},
+    theme_plugin::{ThemeCache, ThemeStyle, Themes},
     widget_style::{
-        ButtonStyle, Classes, HasClasses as _, StyleStruct as _, WidgetState, WidgetStyle,
+        BaseStyle, ButtonStyle, Classes, HasClasses as _, WidgetState, WidgetStyle as _,
     },
 };
 use logos::Logos;
@@ -79,16 +79,16 @@ impl ESSEngine {
 }
 
 /// This implementation basically do nothing. This is only the minimum requirement with caching.
-impl ThemeStyle<WidgetStyle> for ESSEngine {
-    fn style(&mut self, classes: &Classes, state: WidgetState) -> WidgetStyle {
-        self.cache.get(classes, state, || {
-            WidgetStyle::default_style(classes, state)
-        })
+impl ThemeStyle<BaseStyle> for ESSEngine {
+    fn style(&mut self, themes: &Themes, classes: &Classes, state: WidgetState) -> BaseStyle {
+        let current = themes.get::<BaseStyle>(classes, state);
+        self.cache
+            .get(classes, state, || BaseStyle::default_style(classes, state))
     }
 }
 
 impl ThemeStyle<ButtonStyle> for ESSEngine {
-    fn style(&mut self, classes: &Classes, state: WidgetState) -> ButtonStyle {
+    fn style(&mut self, themes: &Themes, classes: &Classes, state: WidgetState) -> ButtonStyle {
         self.cache.get(classes, state, || {
             let mut default = ButtonStyle::default_style(classes, state);
             for classe in classes.list() {

examples/styling_engine/src/main.rs

@@ -1,7 +1,7 @@
 #![cfg_attr(not(debug_assertions), windows_subsystem = "windows")] // hide console window on Windows in release
 #![expect(rustdoc::missing_crate_level_docs)] // it's an example
 
-use eframe::egui::widget_style::WidgetStyle;
+use eframe::egui::widget_style::BaseStyle;
 use eframe::egui::{
     self, Button, Frame, Margin, Panel, UiBuilder,
     widget_style::{ButtonStyle, HasClasses as _},
@@ -36,8 +36,8 @@ fn main() -> eframe::Result {
     eframe::run_ui_native("My egui App", options, move |ui, _frame| {
         // Register the theme plugin and which style they implement
         if let Ok(engine) = ESSEngine::try_parse(&style_code) {
-            ui.add_theme::<WidgetStyle>(engine.clone());
-            ui.add_theme::<ButtonStyle>(engine);
+            ui.add_widget_theme::<BaseStyle>(engine.clone());
+            ui.add_widget_theme::<ButtonStyle>(engine);
         }
 
         ui.scope_builder(UiBuilder::new().with_class("body"), |ui| {
@@ -54,8 +54,8 @@ fn main() -> eframe::Result {
                         && let Ok(engine) = ESSEngine::try_parse(&style_code)
                     {
                         // Overwrite the current theme with the new one.clear
-                        ui.replace_theme::<WidgetStyle>(engine.clone());
-                        ui.replace_theme::<ButtonStyle>(engine);
+                        ui.replace_widget_theme::<BaseStyle>(engine.clone());
+                        ui.replace_widget_theme::<ButtonStyle>(engine);
                     }
                 });
             });