Add image and hash snapshot-based testing to `iced_test`

17 files changed, 280 insertions, 105 deletions

diff --git a/Cargo.toml b/Cargo.toml
index 92687812..0b9833d6 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -166,11 +166,13 @@ num-traits = "0.2"
 once_cell = "1.0"
 ouroboros = "0.18"
 palette = "0.7"
+png = "0.17"
 pulldown-cmark = "0.11"
 qrcode = { version = "0.13", default-features = false }
 raw-window-handle = "0.6"
 resvg = "0.42"
 rustc-hash = "2.0"
+sha2 = "0.10"
 smol = "1.0"
 smol_str = "0.2"
 softbuffer = "0.4"
diff --git a/core/src/theme.rs b/core/src/theme.rs
index 6b2c04da..23480cec 100644
--- a/core/src/theme.rs
+++ b/core/src/theme.rs
@@ -3,6 +3,8 @@ pub mod palette;
 
 pub use palette::Palette;
 
+use crate::Color;
+
 use std::fmt;
 use std::sync::Arc;
 
@@ -246,3 +248,35 @@ impl fmt::Display for Custom {
         write!(f, "{}", self.name)
     }
 }
+
+/// The base style of a [`Theme`].
+#[derive(Debug, Clone, Copy, PartialEq)]
+pub struct Style {
+    /// The background [`Color`] of the application.
+    pub background_color: Color,
+
+    /// The default text [`Color`] of the application.
+    pub text_color: Color,
+}
+
+/// The default blank style of a [`Theme`].
+pub trait Base {
+    /// Returns the default base [`Style`] of a [`Theme`].
+    fn base(&self) -> Style;
+}
+
+impl Base for Theme {
+    fn base(&self) -> Style {
+        default(self)
+    }
+}
+
+/// The default [`Style`] of a built-in [`Theme`].
+pub fn default(theme: &Theme) -> Style {
+    let palette = theme.extended_palette();
+
+    Style {
+        background_color: palette.background.base.color,
+        text_color: palette.background.base.text,
+    }
+}
diff --git a/core/src/window.rs b/core/src/window.rs
index 448ffc45..a3389998 100644
--- a/core/src/window.rs
+++ b/core/src/window.rs
@@ -1,5 +1,6 @@
 //! Build window-based GUI applications.
 pub mod icon;
+pub mod screenshot;
 pub mod settings;
 
 mod event;
@@ -17,5 +18,6 @@ pub use level::Level;
 pub use mode::Mode;
 pub use position::Position;
 pub use redraw_request::RedrawRequest;
+pub use screenshot::Screenshot;
 pub use settings::Settings;
 pub use user_attention::UserAttention;
diff --git a/runtime/src/window/screenshot.rs b/core/src/window/screenshot.rs
index d9adbc01..424168bb 100644
--- a/runtime/src/window/screenshot.rs
+++ b/core/src/window/screenshot.rs
@@ -1,5 +1,5 @@
 //! Take screenshots of a window.
-use crate::core::{Rectangle, Size};
+use crate::{Rectangle, Size};
 
 use bytes::Bytes;
 use std::fmt::{Debug, Formatter};
diff --git a/examples/gradient/src/main.rs b/examples/gradient/src/main.rs
index b2de069f..910ea9fc 100644
--- a/examples/gradient/src/main.rs
+++ b/examples/gradient/src/main.rs
@@ -1,5 +1,5 @@
-use iced::application;
 use iced::gradient;
+use iced::theme;
 use iced::widget::{
     checkbox, column, container, horizontal_space, row, slider, text,
 };
@@ -95,16 +95,14 @@ impl Gradient {
         .into()
     }
 
-    fn style(&self, theme: &Theme) -> application::Appearance {
-        use application::DefaultStyle;
-
+    fn style(&self, theme: &Theme) -> theme::Style {
         if self.transparent {
-            application::Appearance {
+            theme::Style {
                 background_color: Color::TRANSPARENT,
                 text_color: theme.palette().text,
             }
         } else {
-            Theme::default_style(theme)
+            theme::default(theme)
         }
     }
 }
diff --git a/examples/todos/snapshots/creates_a_new_task.sha256 b/examples/todos/snapshots/creates_a_new_task.sha256
new file mode 100644
index 00000000..fcfee315
--- /dev/null
+++ b/examples/todos/snapshots/creates_a_new_task.sha256
@@ -0,0 +1 @@
+5047c10c4ea050393b686185b8d03b3c3738b47182f9892fb68df589ec46bd4b
\ No newline at end of file
diff --git a/examples/todos/src/main.rs b/examples/todos/src/main.rs
index 51d09962..ff38c6ce 100644
--- a/examples/todos/src/main.rs
+++ b/examples/todos/src/main.rs
@@ -15,7 +15,7 @@ pub fn main() -> iced::Result {
 
     iced::application(Todos::title, Todos::update, Todos::view)
         .subscription(Todos::subscription)
-        .font(include_bytes!("../fonts/icons.ttf").as_slice())
+        .font(Todos::ICON_FONT)
         .window_size((500.0, 800.0))
         .run_with(Todos::new)
 }
@@ -48,6 +48,8 @@ enum Message {
 }
 
 impl Todos {
+    const ICON_FONT: &[u8] = include_bytes!("../fonts/icons.ttf");
+
     fn new() -> (Self, Command<Message>) {
         (
             Self::Loading,
@@ -449,11 +451,10 @@ fn empty_message(message: &str) -> Element<'_, Message> {
 }
 
 // Fonts
-const ICONS: Font = Font::with_name("Iced-Todos-Icons");
 
 fn icon(unicode: char) -> Text<'static> {
     text(unicode.to_string())
-        .font(ICONS)
+        .font(Font::with_name("Iced-Todos-Icons"))
         .width(20)
         .align_x(Center)
 }
@@ -594,6 +595,8 @@ mod tests {
 
     #[test]
     fn it_creates_a_new_task() -> Result<(), test::Error> {
+        test::load_font(Todos::ICON_FONT)?;
+
         let (mut todos, _command) = Todos::new();
         let _command = todos.update(Message::Loaded(Err(LoadError::File)));
 
@@ -610,6 +613,12 @@ mod tests {
         let mut interface = test::interface(todos.view());
         let _ = interface.find(selector::text("Create the universe"))?;
 
+        let snapshot = interface.snapshot()?;
+        assert!(
+            snapshot.matches_hash("snapshots/creates_a_new_task")?,
+            "snapshots should match!"
+        );
+
         Ok(())
     }
 }
diff --git a/runtime/src/window.rs b/runtime/src/window.rs
index 382f4518..0ebdba2f 100644
--- a/runtime/src/window.rs
+++ b/runtime/src/window.rs
@@ -1,11 +1,7 @@
 //! Build window-based GUI applications.
-pub mod screenshot;
-
-pub use screenshot::Screenshot;
-
 use crate::core::time::Instant;
 use crate::core::window::{
-    Event, Icon, Id, Level, Mode, Settings, UserAttention,
+    Event, Icon, Id, Level, Mode, Screenshot, Settings, UserAttention,
 };
 use crate::core::{Point, Size};
 use crate::futures::event;
diff --git a/src/application.rs b/src/application.rs
index 2ba764be..c79ed62b 100644
--- a/src/application.rs
+++ b/src/application.rs
@@ -31,6 +31,7 @@
 //! }
 //! ```
 use crate::program::{self, Program};
+use crate::theme;
 use crate::window;
 use crate::{
     Element, Executor, Font, Result, Settings, Size, Subscription, Task,
@@ -38,8 +39,6 @@ use crate::{
 
 use std::borrow::Cow;
 
-pub use crate::shell::program::{Appearance, DefaultStyle};
-
 /// Creates an iced [`Application`] given its title, update, and view logic.
 ///
 /// # Example
@@ -76,7 +75,7 @@ pub fn application<State, Message, Theme, Renderer>(
 where
     State: 'static,
     Message: Send + std::fmt::Debug + 'static,
-    Theme: Default + DefaultStyle,
+    Theme: Default + theme::Base,
     Renderer: program::Renderer,
 {
     use std::marker::PhantomData;
@@ -94,7 +93,7 @@ where
         for Instance<State, Message, Theme, Renderer, Update, View>
     where
         Message: Send + std::fmt::Debug + 'static,
-        Theme: Default + DefaultStyle,
+        Theme: Default + theme::Base,
         Renderer: program::Renderer,
         Update: self::Update<State, Message>,
         View: for<'a> self::View<'a, State, Message, Theme, Renderer>,
@@ -352,7 +351,7 @@ impl<P: Program> Application<P> {
     /// Sets the style logic of the [`Application`].
     pub fn style(
         self,
-        f: impl Fn(&P::State, &P::Theme) -> Appearance,
+        f: impl Fn(&P::State, &P::Theme) -> theme::Style,
     ) -> Application<
         impl Program<State = P::State, Message = P::Message, Theme = P::Theme>,
     > {
diff --git a/src/daemon.rs b/src/daemon.rs
index 81254bf9..fd6d0278 100644
--- a/src/daemon.rs
+++ b/src/daemon.rs
@@ -1,13 +1,12 @@
 //! Create and run daemons that run in the background.
 use crate::application;
 use crate::program::{self, Program};
+use crate::theme;
 use crate::window;
 use crate::{Element, Executor, Font, Result, Settings, Subscription, Task};
 
 use std::borrow::Cow;
 
-pub use crate::shell::program::{Appearance, DefaultStyle};
-
 /// Creates an iced [`Daemon`] given its title, update, and view logic.
 ///
 /// A [`Daemon`] will not open a window by default, but will run silently
@@ -26,7 +25,7 @@ pub fn daemon<State, Message, Theme, Renderer>(
 where
     State: 'static,
     Message: Send + std::fmt::Debug + 'static,
-    Theme: Default + DefaultStyle,
+    Theme: Default + theme::Base,
     Renderer: program::Renderer,
 {
     use std::marker::PhantomData;
@@ -44,7 +43,7 @@ where
         for Instance<State, Message, Theme, Renderer, Update, View>
     where
         Message: Send + std::fmt::Debug + 'static,
-        Theme: Default + DefaultStyle,
+        Theme: Default + theme::Base,
         Renderer: program::Renderer,
         Update: application::Update<State, Message>,
         View: for<'a> self::View<'a, State, Message, Theme, Renderer>,
@@ -201,7 +200,7 @@ impl<P: Program> Daemon<P> {
     /// Sets the style logic of the [`Daemon`].
     pub fn style(
         self,
-        f: impl Fn(&P::State, &P::Theme) -> Appearance,
+        f: impl Fn(&P::State, &P::Theme) -> theme::Style,
     ) -> Daemon<
         impl Program<State = P::State, Message = P::Message, Theme = P::Theme>,
     > {
diff --git a/src/lib.rs b/src/lib.rs
index d7628ea1..e7486909 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -688,7 +688,7 @@ pub fn run<State, Message, Theme, Renderer>(
 where
     State: Default + 'static,
     Message: std::fmt::Debug + Send + 'static,
-    Theme: Default + program::DefaultStyle + 'static,
+    Theme: Default + theme::Base + 'static,
     Renderer: program::Renderer + 'static,
 {
     application(title, update, view).run()
diff --git a/src/program.rs b/src/program.rs
index 94cb9a7d..ace4da74 100644
--- a/src/program.rs
+++ b/src/program.rs
@@ -1,11 +1,10 @@
 use crate::core::text;
 use crate::graphics::compositor;
 use crate::shell;
+use crate::theme;
 use crate::window;
 use crate::{Element, Executor, Result, Settings, Subscription, Task};
 
-pub use crate::shell::program::{Appearance, DefaultStyle};
-
 /// The internal definition of a [`Program`].
 ///
 /// You should not need to implement this trait directly. Instead, use the
@@ -19,7 +18,7 @@ pub trait Program: Sized {
     type Message: Send + std::fmt::Debug + 'static;
 
     /// The theme of the program.
-    type Theme: Default + DefaultStyle;
+    type Theme: Default + theme::Base;
 
     /// The renderer of the program.
     type Renderer: Renderer;
@@ -51,11 +50,11 @@ pub trait Program: Sized {
     }
 
     fn theme(&self, _state: &Self::State, _window: window::Id) -> Self::Theme {
-        Self::Theme::default()
+        <Self::Theme as Default>::default()
     }
 
-    fn style(&self, _state: &Self::State, theme: &Self::Theme) -> Appearance {
-        DefaultStyle::default_style(theme)
+    fn style(&self, _state: &Self::State, theme: &Self::Theme) -> theme::Style {
+        theme::Base::base(theme)
     }
 
     fn scale_factor(&self, _state: &Self::State, _window: window::Id) -> f64 {
@@ -153,7 +152,7 @@ pub trait Program: Sized {
                 self.program.theme(&self.state, window)
             }
 
-            fn style(&self, theme: &Self::Theme) -> Appearance {
+            fn style(&self, theme: &Self::Theme) -> theme::Style {
                 self.program.style(&self.state, theme)
             }
 
@@ -252,7 +251,7 @@ pub fn with_title<P: Program>(
             &self,
             state: &Self::State,
             theme: &Self::Theme,
-        ) -> Appearance {
+        ) -> theme::Style {
             self.program.style(state, theme)
         }
 
@@ -322,7 +321,7 @@ pub fn with_subscription<P: Program>(
             &self,
             state: &Self::State,
             theme: &Self::Theme,
-        ) -> Appearance {
+        ) -> theme::Style {
             self.program.style(state, theme)
         }
 
@@ -395,7 +394,7 @@ pub fn with_theme<P: Program>(
             &self,
             state: &Self::State,
             theme: &Self::Theme,
-        ) -> Appearance {
+        ) -> theme::Style {
             self.program.style(state, theme)
         }
 
@@ -409,7 +408,7 @@ pub fn with_theme<P: Program>(
 
 pub fn with_style<P: Program>(
     program: P,
-    f: impl Fn(&P::State, &P::Theme) -> Appearance,
+    f: impl Fn(&P::State, &P::Theme) -> theme::Style,
 ) -> impl Program<State = P::State, Message = P::Message, Theme = P::Theme> {
     struct WithStyle<P, F> {
         program: P,
@@ -418,7 +417,7 @@ pub fn with_style<P: Program>(
 
     impl<P: Program, F> Program for WithStyle<P, F>
     where
-        F: Fn(&P::State, &P::Theme) -> Appearance,
+        F: Fn(&P::State, &P::Theme) -> theme::Style,
     {
         type State = P::State;
         type Message = P::Message;
@@ -430,7 +429,7 @@ pub fn with_style<P: Program>(
             &self,
             state: &Self::State,
             theme: &Self::Theme,
-        ) -> Appearance {
+        ) -> theme::Style {
             (self.style)(state, theme)
         }
 
@@ -535,7 +534,7 @@ pub fn with_scale_factor<P: Program>(
             &self,
             state: &Self::State,
             theme: &Self::Theme,
-        ) -> Appearance {
+        ) -> theme::Style {
             self.program.style(state, theme)
         }
 
@@ -609,7 +608,7 @@ pub fn with_executor<P: Program, E: Executor>(
             &self,
             state: &Self::State,
             theme: &Self::Theme,
-        ) -> Appearance {
+        ) -> theme::Style {
             self.program.style(state, theme)
         }
 
diff --git a/test/Cargo.toml b/test/Cargo.toml
index c09a196d..f6f4f45a 100644
--- a/test/Cargo.toml
+++ b/test/Cargo.toml
@@ -19,3 +19,6 @@ iced_tiny_skia.workspace = true
 
 iced_renderer.workspace = true
 iced_renderer.features = ["tiny-skia"]
+
+png.workspace = true
+sha2.workspace = true
diff --git a/test/src/lib.rs b/test/src/lib.rs
index 211ed4a2..c9096211 100644
--- a/test/src/lib.rs
+++ b/test/src/lib.rs
@@ -12,15 +12,26 @@ use iced_tiny_skia as tiny_skia;
 use crate::core::clipboard;
 use crate::core::keyboard;
 use crate::core::mouse;
+use crate::core::theme;
+use crate::core::time;
 use crate::core::widget;
+use crate::core::window;
 use crate::core::{Element, Event, Font, Pixels, Rectangle, Size, SmolStr};
 use crate::renderer::Renderer;
 use crate::runtime::user_interface;
 use crate::runtime::UserInterface;
 
+use std::borrow::Cow;
+use std::fs;
+use std::io;
+use std::path::Path;
+use std::sync::Arc;
+
 pub fn interface<'a, Message, Theme>(
     element: impl Into<Element<'a, Message, Theme, Renderer>>,
 ) -> Interface<'a, Message, Theme, Renderer> {
+    let size = Size::new(512.0, 512.0);
+
     let mut renderer = Renderer::Secondary(tiny_skia::Renderer::new(
         Font::default(),
         Pixels(16.0),
@@ -28,7 +39,7 @@ pub fn interface<'a, Message, Theme>(
 
     let raw = UserInterface::build(
         element,
-        Size::new(1024.0, 1024.0),
+        size,
         user_interface::Cache::default(),
         &mut renderer,
     );
@@ -36,13 +47,24 @@ pub fn interface<'a, Message, Theme>(
     Interface {
         raw,
         renderer,
+        size,
         messages: Vec::new(),
     }
 }
 
+pub fn load_font(font: impl Into<Cow<'static, [u8]>>) -> Result<(), Error> {
+    renderer::graphics::text::font_system()
+        .write()
+        .expect("Write to font system")
+        .load_font(font.into());
+
+    Ok(())
+}
+
 pub struct Interface<'a, Message, Theme, Renderer> {
     raw: UserInterface<'a, Message, Theme, Renderer>,
     renderer: Renderer,
+    size: Size,
     messages: Vec<Message>,
 }
 
@@ -50,9 +72,9 @@ pub struct Target {
     bounds: Rectangle,
 }
 
-impl<Message, Theme, Renderer> Interface<'_, Message, Theme, Renderer>
+impl<Message, Theme> Interface<'_, Message, Theme, Renderer>
 where
-    Renderer: core::Renderer,
+    Theme: Default + theme::Base,
 {
     pub fn find(
         &mut self,
@@ -256,11 +278,129 @@ where
         );
     }
 
+    pub fn snapshot(&mut self) -> Result<Snapshot, Error> {
+        let theme = Theme::default();
+        let base = theme.base();
+
+        let _ = self.raw.update(
+            &[Event::Window(window::Event::RedrawRequested(
+                time::Instant::now(),
+            ))],
+            mouse::Cursor::Unavailable,
+            &mut self.renderer,
+            &mut clipboard::Null,
+            &mut self.messages,
+        );
+
+        let _ = self.raw.draw(
+            &mut self.renderer,
+            &theme,
+            &core::renderer::Style {
+                text_color: base.text_color,
+            },
+            mouse::Cursor::Unavailable,
+        );
+
+        if let Renderer::Secondary(renderer) = &mut self.renderer {
+            let scale_factor = 2.0;
+
+            let viewport = renderer::graphics::Viewport::with_physical_size(
+                Size::new(
+                    (self.size.width * scale_factor).round() as u32,
+                    (self.size.height * scale_factor).round() as u32,
+                ),
+                f64::from(scale_factor),
+            );
+
+            let rgba = tiny_skia::window::compositor::screenshot::<&str>(
+                renderer,
+                &viewport,
+                base.background_color,
+                &[],
+            );
+
+            Ok(Snapshot {
+                screenshot: window::Screenshot::new(
+                    rgba,
+                    viewport.physical_size(),
+                    viewport.scale_factor(),
+                ),
+            })
+        } else {
+            unreachable!()
+        }
+    }
+
     pub fn into_messages(self) -> impl IntoIterator<Item = Message> {
         self.messages
     }
 }
 
+pub struct Snapshot {
+    screenshot: window::Screenshot,
+}
+
+impl Snapshot {
+    pub fn matches_image(&self, path: impl AsRef<Path>) -> Result<bool, Error> {
+        let path = path.as_ref().with_extension("png");
+
+        if path.exists() {
+            let file = fs::File::open(&path)?;
+            let decoder = png::Decoder::new(file);
+
+            let mut reader = decoder.read_info()?;
+            let mut bytes = vec![0; reader.output_buffer_size()];
+            let info = reader.next_frame(&mut bytes)?;
+
+            Ok(self.screenshot.bytes == bytes[..info.buffer_size()])
+        } else {
+            if let Some(directory) = path.parent() {
+                fs::create_dir_all(directory)?;
+            }
+
+            let file = fs::File::create(path)?;
+
+            let mut encoder = png::Encoder::new(
+                file,
+                self.screenshot.size.width,
+                self.screenshot.size.height,
+            );
+            encoder.set_color(png::ColorType::Rgba);
+
+            let mut writer = encoder.write_header()?;
+            writer.write_image_data(&self.screenshot.bytes)?;
+            writer.finish()?;
+
+            Ok(true)
+        }
+    }
+
+    pub fn matches_hash(&self, path: impl AsRef<Path>) -> Result<bool, Error> {
+        use sha2::{Digest, Sha256};
+
+        let path = path.as_ref().with_extension("sha256");
+
+        let hash = {
+            let mut hasher = Sha256::new();
+            hasher.update(&self.screenshot.bytes);
+            format!("{:x}", hasher.finalize())
+        };
+
+        if path.exists() {
+            let saved_hash = fs::read_to_string(&path)?;
+
+            Ok(hash == saved_hash)
+        } else {
+            if let Some(directory) = path.parent() {
+                fs::create_dir_all(directory)?;
+            }
+
+            fs::write(path, hash)?;
+            Ok(true)
+        }
+    }
+}
+
 fn key_press_and_release(
     key: impl Into<keyboard::Key>,
     text: Option<SmolStr>,
@@ -293,4 +433,25 @@ fn key_press_and_release(
 #[derive(Debug, Clone)]
 pub enum Error {
     NotFound(Selector),
+    IOFailed(Arc<io::Error>),
+    PngDecodingFailed(Arc<png::DecodingError>),
+    PngEncodingFailed(Arc<png::EncodingError>),
+}
+
+impl From<io::Error> for Error {
+    fn from(error: io::Error) -> Self {
+        Self::IOFailed(Arc::new(error))
+    }
+}
+
+impl From<png::DecodingError> for Error {
+    fn from(error: png::DecodingError) -> Self {
+        Self::PngDecodingFailed(Arc::new(error))
+    }
+}
+
+impl From<png::EncodingError> for Error {
+    fn from(error: png::EncodingError) -> Self {
+        Self::PngEncodingFailed(Arc::new(error))
+    }
 }
diff --git a/winit/src/program.rs b/winit/src/program.rs
index 13873edd..26b713f3 100644
--- a/winit/src/program.rs
+++ b/winit/src/program.rs
@@ -8,10 +8,11 @@ use crate::conversion;
 use crate::core;
 use crate::core::mouse;
 use crate::core::renderer;
+use crate::core::theme;
 use crate::core::time::Instant;
 use crate::core::widget::operation;
 use crate::core::window;
-use crate::core::{Color, Element, Point, Size, Theme};
+use crate::core::{Element, Point, Size};
 use crate::futures::futures::channel::mpsc;
 use crate::futures::futures::channel::oneshot;
 use crate::futures::futures::task;
@@ -46,7 +47,7 @@ use std::sync::Arc;
 pub trait Program
 where
     Self: Sized,
-    Self::Theme: DefaultStyle,
+    Self::Theme: theme::Base,
 {
     /// The type of __messages__ your [`Program`] will produce.
     type Message: std::fmt::Debug + Send;
@@ -106,8 +107,8 @@ where
     fn theme(&self, window: window::Id) -> Self::Theme;
 
     /// Returns the `Style` variation of the `Theme`.
-    fn style(&self, theme: &Self::Theme) -> Appearance {
-        theme.default_style()
+    fn style(&self, theme: &Self::Theme) -> theme::Style {
+        theme::Base::base(theme)
     }
 
     /// Returns the event `Subscription` for the current state of the
@@ -138,37 +139,6 @@ where
     }
 }
 
-/// The appearance of a program.
-#[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 default style of a [`Program`].
-pub trait DefaultStyle {
-    /// Returns the default style of a [`Program`].
-    fn default_style(&self) -> Appearance;
-}
-
-impl DefaultStyle for Theme {
-    fn default_style(&self) -> Appearance {
-        default(self)
-    }
-}
-
-/// The default [`Appearance`] of a [`Program`] with the built-in [`Theme`].
-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 a [`Program`] with an executor, compositor, and the provided
 /// settings.
 pub fn run<P, C>(
@@ -180,7 +150,7 @@ pub fn run<P, C>(
 where
     P: Program + 'static,
     C: Compositor<Renderer = P::Renderer> + 'static,
-    P::Theme: DefaultStyle,
+    P::Theme: theme::Base,
 {
     use winit::event_loop::EventLoop;
 
@@ -674,7 +644,7 @@ async fn run_instance<P, C>(
 ) where
     P: Program + 'static,
     C: Compositor<Renderer = P::Renderer> + 'static,
-    P::Theme: DefaultStyle,
+    P::Theme: theme::Base,
 {
     use winit::event;
     use winit::event_loop::ControlFlow;
@@ -1170,7 +1140,7 @@ fn build_user_interface<'a, P: Program>(
     id: window::Id,
 ) -> UserInterface<'a, P::Message, P::Theme, P::Renderer>
 where
-    P::Theme: DefaultStyle,
+    P::Theme: theme::Base,
 {
     debug.view_started();
     let view = program.view(id);
@@ -1189,7 +1159,7 @@ fn update<P: Program, E: Executor>(
     debug: &mut Debug,
     messages: &mut Vec<P::Message>,
 ) where
-    P::Theme: DefaultStyle,
+    P::Theme: theme::Base,
 {
     for message in messages.drain(..) {
         debug.log_message(&message);
@@ -1226,7 +1196,7 @@ fn run_action<P, C>(
 ) where
     P: Program,
     C: Compositor<Renderer = P::Renderer> + 'static,
-    P::Theme: DefaultStyle,
+    P::Theme: theme::Base,
 {
     use crate::runtime::clipboard;
     use crate::runtime::system;
@@ -1461,7 +1431,7 @@ fn run_action<P, C>(
                         &debug.overlay(),
                     );
 
-                    let _ = channel.send(window::Screenshot::new(
+                    let _ = channel.send(core::window::Screenshot::new(
                         bytes,
                         window.state.physical_size(),
                         window.state.viewport().scale_factor(),
@@ -1536,7 +1506,7 @@ pub fn build_user_interfaces<'a, P: Program, C>(
 ) -> FxHashMap<window::Id, UserInterface<'a, P::Message, P::Theme, P::Renderer>>
 where
     C: Compositor<Renderer = P::Renderer>,
-    P::Theme: DefaultStyle,
+    P::Theme: theme::Base,
 {
     cached_user_interfaces
         .drain()
diff --git a/winit/src/program/state.rs b/winit/src/program/state.rs
index b8a58960..e883d04a 100644
--- a/winit/src/program/state.rs
+++ b/winit/src/program/state.rs
@@ -1,17 +1,18 @@
 use crate::conversion;
-use crate::core::{mouse, window};
+use crate::core::{mouse, theme, window};
 use crate::core::{Color, Size};
 use crate::graphics::Viewport;
-use crate::program::{self, Program};
-use std::fmt::{Debug, Formatter};
+use crate::program::Program;
 
 use winit::event::{Touch, WindowEvent};
 use winit::window::Window;
 
+use std::fmt::{Debug, Formatter};
+
 /// The state of a multi-windowed [`Program`].
 pub struct State<P: Program>
 where
-    P::Theme: program::DefaultStyle,
+    P::Theme: theme::Base,
 {
     title: String,
     scale_factor: f64,
@@ -20,12 +21,12 @@ where
     cursor_position: Option<winit::dpi::PhysicalPosition<f64>>,
     modifiers: winit::keyboard::ModifiersState,
     theme: P::Theme,
-    appearance: program::Appearance,
+    style: theme::Style,
 }
 
 impl<P: Program> Debug for State<P>
 where
-    P::Theme: program::DefaultStyle,
+    P::Theme: theme::Base,
 {
     fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
         f.debug_struct("multi_window::State")
@@ -34,14 +35,14 @@ where
             .field("viewport", &self.viewport)
             .field("viewport_version", &self.viewport_version)
             .field("cursor_position", &self.cursor_position)
-            .field("appearance", &self.appearance)
+            .field("style", &self.style)
             .finish()
     }
 }
 
 impl<P: Program> State<P>
 where
-    P::Theme: program::DefaultStyle,
+    P::Theme: theme::Base,
 {
     /// Creates a new [`State`] for the provided [`Program`]'s `window`.
     pub fn new(
@@ -52,7 +53,7 @@ where
         let title = application.title(window_id);
         let scale_factor = application.scale_factor(window_id);
         let theme = application.theme(window_id);
-        let appearance = application.style(&theme);
+        let style = application.style(&theme);
 
         let viewport = {
             let physical_size = window.inner_size();
@@ -71,7 +72,7 @@ where
             cursor_position: None,
             modifiers: winit::keyboard::ModifiersState::default(),
             theme,
-            appearance,
+            style,
         }
     }
 
@@ -127,12 +128,12 @@ where
 
     /// Returns the current background [`Color`] of the [`State`].
     pub fn background_color(&self) -> Color {
-        self.appearance.background_color
+        self.style.background_color
     }
 
     /// Returns the current text [`Color`] of the [`State`].
     pub fn text_color(&self) -> Color {
-        self.appearance.text_color
+        self.style.text_color
     }
 
     /// Processes the provided window event and updates the [`State`] accordingly.
@@ -237,6 +238,6 @@ where
 
         // Update theme and appearance
         self.theme = application.theme(window_id);
-        self.appearance = application.style(&self.theme);
+        self.style = application.style(&self.theme);
     }
 }
diff --git a/winit/src/program/window_manager.rs b/winit/src/program/window_manager.rs
index 10a973fe..451b2caf 100644
--- a/winit/src/program/window_manager.rs
+++ b/winit/src/program/window_manager.rs
@@ -1,9 +1,10 @@
 use crate::core::mouse;
+use crate::core::theme;
 use crate::core::time::Instant;
 use crate::core::window::Id;
 use crate::core::{Point, Size};
 use crate::graphics::Compositor;
-use crate::program::{DefaultStyle, Program, State};
+use crate::program::{Program, State};
 
 use std::collections::BTreeMap;
 use std::sync::Arc;
@@ -14,7 +15,7 @@ pub struct WindowManager<P, C>
 where
     P: Program,
     C: Compositor<Renderer = P::Renderer>,
-    P::Theme: DefaultStyle,
+    P::Theme: theme::Base,
 {
     aliases: BTreeMap<winit::window::WindowId, Id>,
     entries: BTreeMap<Id, Window<P, C>>,
@@ -24,7 +25,7 @@ impl<P, C> WindowManager<P, C>
 where
     P: Program,
     C: Compositor<Renderer = P::Renderer>,
-    P::Theme: DefaultStyle,
+    P::Theme: theme::Base,
 {
     pub fn new() -> Self {
         Self {
@@ -132,7 +133,7 @@ impl<P, C> Default for WindowManager<P, C>
 where
     P: Program,
     C: Compositor<Renderer = P::Renderer>,
-    P::Theme: DefaultStyle,
+    P::Theme: theme::Base,
 {
     fn default() -> Self {
         Self::new()
@@ -144,7 +145,7 @@ pub struct Window<P, C>
 where
     P: Program,
     C: Compositor<Renderer = P::Renderer>,
-    P::Theme: DefaultStyle,
+    P::Theme: theme::Base,
 {
     pub raw: Arc<winit::window::Window>,
     pub state: State<P>,
@@ -160,7 +161,7 @@ impl<P, C> Window<P, C>
 where
     P: Program,
     C: Compositor<Renderer = P::Renderer>,
-    P::Theme: DefaultStyle,
+    P::Theme: theme::Base,
 {
     pub fn position(&self) -> Option<Point> {
         self.raw