Let a Theme control the background color of an application

... and remove `Application::background_color`

examples/pure/game_of_life/src/main.rs

@@ -12,7 +12,7 @@ use iced::pure::{Application, Element};
 use iced::theme::{self, Theme};
 use iced::time;
 use iced::window;
-use iced::{Alignment, Color, Command, Length, Settings, Subscription};
+use iced::{Alignment, Command, Length, Settings, Subscription};
 use preset::Preset;
 use std::time::{Duration, Instant};
 
@@ -71,10 +71,6 @@ impl Application for GameOfLife {
         String::from("Game of Life - Iced")
     }
 
-    fn background_color(&self) -> Color {
-        style::BACKGROUND
-    }
-
     fn update(&mut self, message: Message) -> Command<Message> {
         match message {
             Message::Grid(message, version) => {

glutin/src/application.rs

@@ -9,6 +9,7 @@ use iced_winit::application;
 use iced_winit::conversion;
 use iced_winit::futures;
 use iced_winit::futures::channel::mpsc;
+use iced_winit::theme::{self, Definition as _};
 use iced_winit::user_interface;
 use iced_winit::{Clipboard, Debug, Proxy, Settings};
 
@@ -25,6 +26,7 @@ where
     A: Application + 'static,
     E: Executor + 'static,
     C: window::GLCompositor<Renderer = A::Renderer> + 'static,
+    <A::Renderer as iced_native::Renderer>::Theme: theme::Definition,
 {
     use futures::task;
     use futures::Future;
@@ -203,6 +205,7 @@ async fn run_instance<A, E, C>(
     A: Application + 'static,
     E: Executor + 'static,
     C: window::GLCompositor<Renderer = A::Renderer> + 'static,
+    <A::Renderer as iced_native::Renderer>::Theme: theme::Definition,
 {
     use glutin::event;
     use iced_winit::futures::stream::StreamExt;
@@ -376,7 +379,7 @@ async fn run_instance<A, E, C>(
                 compositor.present(
                     &mut renderer,
                     state.viewport(),
-                    state.background_color(),
+                    theme.background_color(),
                     &debug.overlay(),
                 );
 

src/application.rs

@@ -1,5 +1,6 @@
+use crate::theme;
 use crate::window;
-use crate::{Color, Command, Element, Executor, Settings, Subscription};
+use crate::{Command, Element, Executor, Settings, Subscription};
 
 /// An interactive cross-platform application.
 ///
@@ -101,7 +102,7 @@ pub trait Application: Sized {
     type Message: std::fmt::Debug + Send;
 
     /// The theme of your [`Application`].
-    type Theme: Default;
+    type Theme: Default + theme::Definition;
 
     /// The data needed to initialize your [`Application`].
     type Flags;
@@ -167,13 +168,6 @@ pub trait Application: Sized {
         window::Mode::Windowed
     }
 
-    /// Returns the background color of the [`Application`].
-    ///
-    /// By default, it returns [`Color::WHITE`].
-    fn background_color(&self) -> Color {
-        Color::WHITE
-    }
-
     /// Returns the scale factor of the [`Application`].
     ///
     /// It can be used to dynamically control the size of the UI at runtime
@@ -277,10 +271,6 @@ where
         self.0.subscription()
     }
 
-    fn background_color(&self) -> Color {
-        self.0.background_color()
-    }
-
     fn scale_factor(&self) -> f64 {
         self.0.scale_factor()
     }

src/pure/application.rs

@@ -1,6 +1,7 @@
 use crate::pure::{self, Pure};
+use crate::theme;
 use crate::window;
-use crate::{Color, Command, Executor, Settings, Subscription};
+use crate::{Command, Executor, Settings, Subscription};
 
 /// A pure version of [`Application`].
 ///
@@ -22,7 +23,7 @@ pub trait Application: Sized {
     type Message: std::fmt::Debug + Send;
 
     /// The theme of your [`Application`].
-    type Theme: Default;
+    type Theme: Default + theme::Definition;
 
     /// The data needed to initialize your [`Application`].
     type Flags;
@@ -88,13 +89,6 @@ pub trait Application: Sized {
         window::Mode::Windowed
     }
 
-    /// Returns the background color of the [`Application`].
-    ///
-    /// By default, it returns [`Color::WHITE`].
-    fn background_color(&self) -> Color {
-        Color::WHITE
-    }
-
     /// Returns the scale factor of the [`Application`].
     ///
     /// It can be used to dynamically control the size of the UI at runtime
@@ -185,10 +179,6 @@ where
         A::mode(&self.application)
     }
 
-    fn background_color(&self) -> Color {
-        A::background_color(&self.application)
-    }
-
     fn scale_factor(&self) -> f64 {
         A::scale_factor(&self.application)
     }

src/pure/sandbox.rs

@@ -1,5 +1,5 @@
 use crate::pure;
-use crate::{Color, Command, Error, Settings, Subscription, Theme};
+use crate::{Command, Error, Settings, Subscription, Theme};
 
 /// A pure version of [`Sandbox`].
 ///
@@ -44,13 +44,6 @@ pub trait Sandbox {
         Theme::default()
     }
 
-    /// Returns the background color of the [`Sandbox`].
-    ///
-    /// By default, it returns [`Color::WHITE`].
-    fn background_color(&self) -> Color {
-        Color::WHITE
-    }
-
     /// Returns the scale factor of the [`Sandbox`].
     ///
     /// It can be used to dynamically control the size of the UI at runtime
@@ -120,10 +113,6 @@ where
         Subscription::none()
     }
 
-    fn background_color(&self) -> Color {
-        T::background_color(self)
-    }
-
     fn scale_factor(&self) -> f64 {
         T::scale_factor(self)
     }

src/sandbox.rs

@@ -1,5 +1,5 @@
 use crate::{
-    Application, Color, Command, Element, Error, Settings, Subscription, Theme,
+    Application, Command, Element, Error, Settings, Subscription, Theme,
 };
 
 /// A sandboxed [`Application`].
@@ -121,13 +121,6 @@ pub trait Sandbox {
         Theme::default()
     }
 
-    /// Returns the background color of the [`Sandbox`].
-    ///
-    /// By default, it returns [`Color::WHITE`].
-    fn background_color(&self) -> Color {
-        Color::WHITE
-    }
-
     /// Returns the scale factor of the [`Sandbox`].
     ///
     /// It can be used to dynamically control the size of the UI at runtime
@@ -197,10 +190,6 @@ where
         Subscription::none()
     }
 
-    fn background_color(&self) -> Color {
-        T::background_color(self)
-    }
-
     fn scale_factor(&self) -> f64 {
         T::scale_factor(self)
     }

style/src/theme.rs

@@ -4,7 +4,7 @@ pub use self::palette::Palette;
 
 use crate::button;
 
-use iced_core::Background;
+use iced_core::{Background, Color};
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub enum Theme {
@@ -34,6 +34,18 @@ impl Default for Theme {
     }
 }
 
+pub trait Definition {
+    fn background_color(&self) -> Color;
+}
+
+impl Definition for Theme {
+    fn background_color(&self) -> Color {
+        let palette = self.extended_palette();
+
+        palette.background.base
+    }
+}
+
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub enum Button {
     Primary,

winit/src/application.rs

@@ -6,9 +6,10 @@ pub use state::State;
 use crate::clipboard::{self, Clipboard};
 use crate::conversion;
 use crate::mouse;
+use crate::theme::{self, Definition as _};
 use crate::{
-    Color, Command, Debug, Error, Executor, Mode, Proxy, Runtime, Settings,
-    Size, Subscription,
+    Command, Debug, Error, Executor, Mode, Proxy, Runtime, Settings, Size,
+    Subscription,
 };
 
 use iced_futures::futures;
@@ -77,13 +78,6 @@ pub trait Application: Program {
         Mode::Windowed
     }
 
-    /// Returns the background [`Color`] of the [`Application`].
-    ///
-    /// By default, it returns [`Color::WHITE`].
-    fn background_color(&self) -> Color {
-        Color::WHITE
-    }
-
     /// Returns the scale factor of the [`Application`].
     ///
     /// It can be used to dynamically control the size of the UI at runtime
@@ -115,6 +109,7 @@ where
     A: Application + 'static,
     E: Executor + 'static,
     C: window::Compositor<Renderer = A::Renderer> + 'static,
+    <A::Renderer as iced_native::Renderer>::Theme: theme::Definition,
 {
     use futures::task;
     use futures::Future;
@@ -250,6 +245,7 @@ async fn run_instance<A, E, C>(
     A: Application + 'static,
     E: Executor + 'static,
     C: window::Compositor<Renderer = A::Renderer> + 'static,
+    <A::Renderer as iced_native::Renderer>::Theme: theme::Definition,
 {
     use iced_futures::futures::stream::StreamExt;
     use winit::event;
@@ -425,7 +421,7 @@ async fn run_instance<A, E, C>(
                     &mut renderer,
                     &mut surface,
                     state.viewport(),
-                    state.background_color(),
+                    theme.background_color(),
                     &debug.overlay(),
                 ) {
                     Ok(()) => {

winit/src/application/state.rs

@@ -1,5 +1,5 @@
 use crate::conversion;
-use crate::{Application, Color, Debug, Mode, Point, Size, Viewport};
+use crate::{Application, Debug, Mode, Point, Size, Viewport};
 
 use std::marker::PhantomData;
 use winit::event::{Touch, WindowEvent};
@@ -10,7 +10,6 @@ use winit::window::Window;
 pub struct State<A: Application> {
     title: String,
     mode: Mode,
-    background_color: Color,
     scale_factor: f64,
     viewport: Viewport,
     viewport_version: usize,
@@ -24,7 +23,6 @@ impl<A: Application> State<A> {
     pub fn new(application: &A, window: &Window) -> Self {
         let title = application.title();
         let mode = application.mode();
-        let background_color = application.background_color();
         let scale_factor = application.scale_factor();
 
         let viewport = {
@@ -39,7 +37,6 @@ impl<A: Application> State<A> {
         Self {
             title,
             mode,
-            background_color,
             scale_factor,
             viewport,
             viewport_version: 0,
@@ -50,11 +47,6 @@ impl<A: Application> State<A> {
         }
     }
 
-    /// Returns the current background [`Color`] of the [`State`].
-    pub fn background_color(&self) -> Color {
-        self.background_color
-    }
-
     /// Returns the current [`Viewport`] of the [`State`].
     pub fn viewport(&self) -> &Viewport {
         &self.viewport
@@ -187,9 +179,6 @@ impl<A: Application> State<A> {
             self.mode = new_mode;
         }
 
-        // Update background color
-        self.background_color = application.background_color();
-
         // Update scale factor
         let new_scale_factor = application.scale_factor();