Simplify theming for `Application`

5 files changed, 91 insertions, 41 deletions

diff --git a/winit/src/application.rs b/winit/src/application.rs
index 05a4f070..fbca6ee4 100644
--- a/winit/src/application.rs
+++ b/winit/src/application.rs
@@ -10,7 +10,7 @@ use crate::core::renderer;
 use crate::core::time::Instant;
 use crate::core::widget::operation;
 use crate::core::window;
-use crate::core::{Event, Point, Size};
+use crate::core::{Color, Event, Point, Size};
 use crate::futures::futures;
 use crate::futures::{Executor, Runtime, Subscription};
 use crate::graphics::compositor::{self, Compositor};
@@ -18,7 +18,7 @@ use crate::runtime::clipboard;
 use crate::runtime::program::Program;
 use crate::runtime::user_interface::{self, UserInterface};
 use crate::runtime::{Command, Debug};
-use crate::style::application::{Appearance, StyleSheet};
+use crate::style::Theme;
 use crate::{Clipboard, Error, Proxy, Settings};
 
 use futures::channel::mpsc;
@@ -39,7 +39,7 @@ use std::sync::Arc;
 /// can be toggled by pressing `F12`.
 pub trait Application: Program
 where
-    Self::Theme: StyleSheet,
+    Style<Self::Theme>: Default,
 {
     /// The data needed to initialize your [`Application`].
     type Flags;
@@ -64,8 +64,8 @@ where
     fn theme(&self) -> Self::Theme;
 
     /// Returns the `Style` variation of the `Theme`.
-    fn style(&self) -> <Self::Theme as StyleSheet>::Style {
-        Default::default()
+    fn style(&self, theme: &Self::Theme) -> Appearance {
+        Style::default().resolve(theme)
     }
 
     /// Returns the event `Subscription` for the current state of the
@@ -95,6 +95,58 @@ where
     }
 }
 
+/// The appearance of an application.
+#[derive(Debug, Clone, Copy, PartialEq)]
+pub struct Appearance {
+    /// The background [`Color`] of the application.
+    pub background_color: Color,
+
+    /// The default text [`Color`] of the application.
+    pub text_color: Color,
+}
+
+/// The style of an [`Application`].
+#[derive(Debug, PartialEq, Eq)]
+pub struct Style<Theme>(pub fn(&Theme) -> Appearance);
+
+impl<Theme> Style<Theme> {
+    /// Resolves the [`Style`] with the given `Theme` to produce
+    /// an [`Appearance`].
+    pub fn resolve(self, theme: &Theme) -> Appearance {
+        (self.0)(theme)
+    }
+}
+
+impl<Theme> Clone for Style<Theme> {
+    fn clone(&self) -> Self {
+        *self
+    }
+}
+
+impl<Theme> Copy for Style<Theme> {}
+
+impl<Theme> From<fn(&Theme) -> Appearance> for Style<Theme> {
+    fn from(f: fn(&Theme) -> Appearance) -> Self {
+        Style(f)
+    }
+}
+
+impl Default for Style<Theme> {
+    fn default() -> Self {
+        Style(default)
+    }
+}
+
+/// The default style of an [`Application`].
+pub fn default(theme: &Theme) -> Appearance {
+    let palette = theme.extended_palette();
+
+    Appearance {
+        background_color: palette.background.base.color,
+        text_color: palette.background.base.text,
+    }
+}
+
 /// Runs an [`Application`] with an executor, compositor, and the provided
 /// settings.
 pub fn run<A, E, C>(
@@ -105,7 +157,7 @@ where
     A: Application + 'static,
     E: Executor + 'static,
     C: Compositor<Renderer = A::Renderer> + 'static,
-    A::Theme: StyleSheet,
+    Style<A::Theme>: Default,
 {
     use futures::task;
     use futures::Future;
@@ -289,7 +341,7 @@ async fn run_instance<A, E, C>(
     A: Application + 'static,
     E: Executor + 'static,
     C: Compositor<Renderer = A::Renderer> + 'static,
-    A::Theme: StyleSheet,
+    Style<A::Theme>: Default,
 {
     use futures::stream::StreamExt;
     use winit::event;
@@ -612,7 +664,7 @@ pub fn build_user_interface<'a, A: Application>(
     debug: &mut Debug,
 ) -> UserInterface<'a, A::Message, A::Theme, A::Renderer>
 where
-    A::Theme: StyleSheet,
+    Style<A::Theme>: Default,
 {
     debug.view_started();
     let view = application.view();
@@ -643,7 +695,7 @@ pub fn update<A: Application, C, E: Executor>(
     window: &winit::window::Window,
 ) where
     C: Compositor<Renderer = A::Renderer> + 'static,
-    A::Theme: StyleSheet,
+    Style<A::Theme>: Default,
 {
     for message in messages.drain(..) {
         debug.log_message(&message);
@@ -694,7 +746,7 @@ pub fn run_command<A, C, E>(
     A: Application,
     E: Executor,
     C: Compositor<Renderer = A::Renderer> + 'static,
-    A::Theme: StyleSheet,
+    Style<A::Theme>: Default,
 {
     use crate::runtime::command;
     use crate::runtime::system;
diff --git a/winit/src/application/state.rs b/winit/src/application/state.rs
index c17a3bcc..b3bdb3a3 100644
--- a/winit/src/application/state.rs
+++ b/winit/src/application/state.rs
@@ -1,4 +1,4 @@
-use crate::application::{self, StyleSheet as _};
+use crate::application;
 use crate::conversion;
 use crate::core::mouse;
 use crate::core::{Color, Size};
@@ -14,7 +14,7 @@ use winit::window::Window;
 #[allow(missing_debug_implementations)]
 pub struct State<A: Application>
 where
-    A::Theme: application::StyleSheet,
+    application::Style<A::Theme>: Default,
 {
     title: String,
     scale_factor: f64,
@@ -29,14 +29,14 @@ where
 
 impl<A: Application> State<A>
 where
-    A::Theme: application::StyleSheet,
+    application::Style<A::Theme>: Default,
 {
     /// Creates a new [`State`] for the provided [`Application`] and window.
     pub fn new(application: &A, window: &Window) -> Self {
         let title = application.title();
         let scale_factor = application.scale_factor();
         let theme = application.theme();
-        let appearance = theme.appearance(&application.style());
+        let appearance = application.style(&theme);
 
         let viewport = {
             let physical_size = window.inner_size();
@@ -216,6 +216,6 @@ where
 
         // Update theme and appearance
         self.theme = application.theme();
-        self.appearance = self.theme.appearance(&application.style());
+        self.appearance = application.style(&self.theme);
     }
 }
diff --git a/winit/src/multi_window.rs b/winit/src/multi_window.rs
index 03066d6c..19951ed3 100644
--- a/winit/src/multi_window.rs
+++ b/winit/src/multi_window.rs
@@ -20,9 +20,10 @@ use crate::runtime::command::{self, Command};
 use crate::runtime::multi_window::Program;
 use crate::runtime::user_interface::{self, UserInterface};
 use crate::runtime::Debug;
-use crate::style::application::StyleSheet;
 use crate::{Clipboard, Error, Proxy, Settings};
 
+pub use crate::application::{default, Appearance, Style};
+
 use std::collections::HashMap;
 use std::mem::ManuallyDrop;
 use std::sync::Arc;
@@ -41,7 +42,7 @@ use std::time::Instant;
 /// can be toggled by pressing `F12`.
 pub trait Application: Program
 where
-    Self::Theme: StyleSheet,
+    Style<Self::Theme>: Default,
 {
     /// The data needed to initialize your [`Application`].
     type Flags;
@@ -66,8 +67,8 @@ where
     fn theme(&self, window: window::Id) -> Self::Theme;
 
     /// Returns the `Style` variation of the `Theme`.
-    fn style(&self) -> <Self::Theme as StyleSheet>::Style {
-        Default::default()
+    fn style(&self, theme: &Self::Theme) -> Appearance {
+        Style::default().resolve(theme)
     }
 
     /// Returns the event `Subscription` for the current state of the
@@ -108,7 +109,7 @@ where
     A: Application + 'static,
     E: Executor + 'static,
     C: Compositor<Renderer = A::Renderer> + 'static,
-    A::Theme: StyleSheet,
+    Style<A::Theme>: Default,
 {
     use winit::event_loop::EventLoopBuilder;
 
@@ -349,7 +350,7 @@ async fn run_instance<A, E, C>(
     A: Application + 'static,
     E: Executor + 'static,
     C: Compositor<Renderer = A::Renderer> + 'static,
-    A::Theme: StyleSheet,
+    Style<A::Theme>: Default,
 {
     use winit::event;
     use winit::event_loop::ControlFlow;
@@ -819,7 +820,7 @@ fn build_user_interface<'a, A: Application>(
     id: window::Id,
 ) -> UserInterface<'a, A::Message, A::Theme, A::Renderer>
 where
-    A::Theme: StyleSheet,
+    Style<A::Theme>: Default,
 {
     debug.view_started();
     let view = application.view(id);
@@ -847,7 +848,7 @@ fn update<A: Application, C, E: Executor>(
     ui_caches: &mut HashMap<window::Id, user_interface::Cache>,
 ) where
     C: Compositor<Renderer = A::Renderer> + 'static,
-    A::Theme: StyleSheet,
+    Style<A::Theme>: Default,
 {
     for message in messages.drain(..) {
         debug.log_message(&message);
@@ -890,7 +891,7 @@ fn run_command<A, C, E>(
     A: Application,
     E: Executor,
     C: Compositor<Renderer = A::Renderer> + 'static,
-    A::Theme: StyleSheet,
+    Style<A::Theme>: Default,
 {
     use crate::runtime::clipboard;
     use crate::runtime::system;
@@ -1216,8 +1217,8 @@ pub fn build_user_interfaces<'a, A: Application, C: Compositor>(
     mut cached_user_interfaces: HashMap<window::Id, user_interface::Cache>,
 ) -> HashMap<window::Id, UserInterface<'a, A::Message, A::Theme, A::Renderer>>
 where
-    A::Theme: StyleSheet,
     C: Compositor<Renderer = A::Renderer>,
+    Style<A::Theme>: Default,
 {
     cached_user_interfaces
         .drain()
diff --git a/winit/src/multi_window/state.rs b/winit/src/multi_window/state.rs
index 2e97a13d..8a332176 100644
--- a/winit/src/multi_window/state.rs
+++ b/winit/src/multi_window/state.rs
@@ -2,18 +2,16 @@ use crate::conversion;
 use crate::core::{mouse, window};
 use crate::core::{Color, Size};
 use crate::graphics::Viewport;
-use crate::multi_window::Application;
-use crate::style::application;
+use crate::multi_window::{self, Application};
 use std::fmt::{Debug, Formatter};
 
-use iced_style::application::StyleSheet;
 use winit::event::{Touch, WindowEvent};
 use winit::window::Window;
 
 /// The state of a multi-windowed [`Application`].
 pub struct State<A: Application>
 where
-    A::Theme: application::StyleSheet,
+    multi_window::Style<A::Theme>: Default,
 {
     title: String,
     scale_factor: f64,
@@ -22,12 +20,12 @@ where
     cursor_position: Option<winit::dpi::PhysicalPosition<f64>>,
     modifiers: winit::keyboard::ModifiersState,
     theme: A::Theme,
-    appearance: application::Appearance,
+    appearance: multi_window::Appearance,
 }
 
 impl<A: Application> Debug for State<A>
 where
-    A::Theme: application::StyleSheet,
+    multi_window::Style<A::Theme>: Default,
 {
     fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
         f.debug_struct("multi_window::State")
@@ -43,7 +41,7 @@ where
 
 impl<A: Application> State<A>
 where
-    A::Theme: application::StyleSheet,
+    multi_window::Style<A::Theme>: Default,
 {
     /// Creates a new [`State`] for the provided [`Application`]'s `window`.
     pub fn new(
@@ -54,7 +52,7 @@ where
         let title = application.title(window_id);
         let scale_factor = application.scale_factor(window_id);
         let theme = application.theme(window_id);
-        let appearance = theme.appearance(&application.style());
+        let appearance = application.style(&theme);
 
         let viewport = {
             let physical_size = window.inner_size();
@@ -236,6 +234,6 @@ where
 
         // Update theme and appearance
         self.theme = application.theme(window_id);
-        self.appearance = self.theme.appearance(&application.style());
+        self.appearance = application.style(&self.theme);
     }
 }
diff --git a/winit/src/multi_window/window_manager.rs b/winit/src/multi_window/window_manager.rs
index 23f3c0ba..2800e923 100644
--- a/winit/src/multi_window/window_manager.rs
+++ b/winit/src/multi_window/window_manager.rs
@@ -2,8 +2,7 @@ use crate::core::mouse;
 use crate::core::window::Id;
 use crate::core::{Point, Size};
 use crate::graphics::Compositor;
-use crate::multi_window::{Application, State};
-use crate::style::application::StyleSheet;
+use crate::multi_window::{Application, State, Style};
 
 use std::collections::BTreeMap;
 use std::sync::Arc;
@@ -12,8 +11,8 @@ use winit::monitor::MonitorHandle;
 #[allow(missing_debug_implementations)]
 pub struct WindowManager<A: Application, C: Compositor>
 where
-    A::Theme: StyleSheet,
     C: Compositor<Renderer = A::Renderer>,
+    Style<A::Theme>: Default,
 {
     aliases: BTreeMap<winit::window::WindowId, Id>,
     entries: BTreeMap<Id, Window<A, C>>,
@@ -23,7 +22,7 @@ impl<A, C> WindowManager<A, C>
 where
     A: Application,
     C: Compositor<Renderer = A::Renderer>,
-    A::Theme: StyleSheet,
+    Style<A::Theme>: Default,
 {
     pub fn new() -> Self {
         Self {
@@ -109,7 +108,7 @@ impl<A, C> Default for WindowManager<A, C>
 where
     A: Application,
     C: Compositor<Renderer = A::Renderer>,
-    A::Theme: StyleSheet,
+    Style<A::Theme>: Default,
 {
     fn default() -> Self {
         Self::new()
@@ -121,7 +120,7 @@ pub struct Window<A, C>
 where
     A: Application,
     C: Compositor<Renderer = A::Renderer>,
-    A::Theme: StyleSheet,
+    Style<A::Theme>: Default,
 {
     pub raw: Arc<winit::window::Window>,
     pub state: State<A>,
@@ -136,7 +135,7 @@ impl<A, C> Window<A, C>
 where
     A: Application,
     C: Compositor<Renderer = A::Renderer>,
-    A::Theme: StyleSheet,
+    Style<A::Theme>: Default,
 {
     pub fn position(&self) -> Option<Point> {
         self.raw