Implement styling for `Scrollable`

9 files changed, 191 insertions, 37 deletions

diff --git a/examples/styling.rs b/examples/styling.rs
index c368ea07..61c8bcba 100644
--- a/examples/styling.rs
+++ b/examples/styling.rs
@@ -1,6 +1,6 @@
 use iced::{
-    button, text_input, Button, Column, Container, Element, Length, Radio, Row,
-    Sandbox, Settings, Text, TextInput,
+    button, scrollable, text_input, Button, Column, Container, Element, Length,
+    Radio, Row, Sandbox, Scrollable, Settings, Text, TextInput,
 };
 
 pub fn main() {
@@ -10,6 +10,7 @@ pub fn main() {
 #[derive(Default)]
 struct Styling {
     theme: style::Theme,
+    scroll: scrollable::State,
     input: text_input::State,
     input_value: String,
     button: button::State,
@@ -76,10 +77,13 @@ impl Sandbox for Styling {
             .push(choose_theme)
             .push(Row::new().spacing(10).push(text_input).push(button));
 
-        Container::new(content)
+        let scrollable = Scrollable::new(&mut self.scroll)
+            .style(self.theme)
+            .push(Container::new(content).width(Length::Fill).center_x());
+
+        Container::new(scrollable)
             .width(Length::Fill)
             .height(Length::Fill)
-            .center_x()
             .center_y()
             .style(self.theme)
             .into()
@@ -87,7 +91,7 @@ impl Sandbox for Styling {
 }
 
 mod style {
-    use iced::{button, container, text_input};
+    use iced::{button, container, scrollable, text_input};
 
     #[derive(Debug, Clone, Copy, PartialEq, Eq)]
     pub enum Theme {
@@ -132,6 +136,15 @@ mod style {
         }
     }
 
+    impl From<Theme> for Box<dyn scrollable::StyleSheet> {
+        fn from(theme: Theme) -> Self {
+            match theme {
+                Theme::Light => Default::default(),
+                Theme::Dark => dark::Scrollable.into(),
+            }
+        }
+    }
+
     mod light {
         use iced::{button, Background, Color, Vector};
 
@@ -161,7 +174,9 @@ mod style {
     }
 
     mod dark {
-        use iced::{button, container, text_input, Background, Color};
+        use iced::{
+            button, container, scrollable, text_input, Background, Color,
+        };
 
         pub struct Container;
 
@@ -239,6 +254,42 @@ mod style {
                     ..self.active()
                 }
             }
+
+            fn pressed(&self) -> button::Style {
+                button::Style {
+                    border_width: 1,
+                    border_color: Color::WHITE,
+                    ..self.hovered()
+                }
+            }
+        }
+
+        pub struct Scrollable;
+
+        impl scrollable::StyleSheet for Scrollable {
+            fn active(&self) -> scrollable::Scrollbar {
+                scrollable::Scrollbar {
+                    background: None,
+                    border_radius: 2,
+                    border_width: 0,
+                    border_color: Color::TRANSPARENT,
+                    scroller: scrollable::Scroller {
+                        color: [1.0, 1.0, 1.0, 0.7].into(),
+                        border_radius: 2,
+                        border_width: 1,
+                        border_color: Color::WHITE,
+                    },
+                }
+            }
+
+            fn hovered(&self) -> scrollable::Scrollbar {
+                scrollable::Scrollbar {
+                    background: Some(Background::Color(
+                        [1.0, 1.0, 1.0, 0.3].into(),
+                    )),
+                    ..self.active()
+                }
+            }
         }
     }
 }
diff --git a/native/src/renderer/null.rs b/native/src/renderer/null.rs
index 96aa132c..0184ac00 100644
--- a/native/src/renderer/null.rs
+++ b/native/src/renderer/null.rs
@@ -73,6 +73,8 @@ impl text::Renderer for Null {
 }
 
 impl scrollable::Renderer for Null {
+    type Style = ();
+
     fn scrollbar(
         &self,
         _bounds: Rectangle,
@@ -91,6 +93,7 @@ impl scrollable::Renderer for Null {
         _is_mouse_over_scrollbar: bool,
         _scrollbar: Option<scrollable::Scrollbar>,
         _offset: u32,
+        _style: &Self::Style,
         _content: Self::Output,
     ) {
     }
diff --git a/native/src/widget/scrollable.rs b/native/src/widget/scrollable.rs
index 9df09b14..a062abd0 100644
--- a/native/src/widget/scrollable.rs
+++ b/native/src/widget/scrollable.rs
@@ -11,14 +11,15 @@ use std::{f32, hash::Hash, u32};
 /// A widget that can vertically display an infinite amount of content with a
 /// scrollbar.
 #[allow(missing_debug_implementations)]
-pub struct Scrollable<'a, Message, Renderer> {
+pub struct Scrollable<'a, Message, Renderer: self::Renderer> {
     state: &'a mut State,
     height: Length,
     max_height: u32,
     content: Column<'a, Message, Renderer>,
+    style: Renderer::Style,
 }
 
-impl<'a, Message, Renderer> Scrollable<'a, Message, Renderer> {
+impl<'a, Message, Renderer: self::Renderer> Scrollable<'a, Message, Renderer> {
     /// Creates a new [`Scrollable`] with the given [`State`].
     ///
     /// [`Scrollable`]: struct.Scrollable.html
@@ -29,6 +30,7 @@ impl<'a, Message, Renderer> Scrollable<'a, Message, Renderer> {
             height: Length::Shrink,
             max_height: u32::MAX,
             content: Column::new(),
+            style: Renderer::Style::default(),
         }
     }
 
@@ -90,6 +92,14 @@ impl<'a, Message, Renderer> Scrollable<'a, Message, Renderer> {
         self
     }
 
+    /// Sets the style of the [`Scrollable`] .
+    ///
+    /// [`Scrollable`]: struct.Scrollable.html
+    pub fn style(mut self, style: impl Into<Renderer::Style>) -> Self {
+        self.style = style.into();
+        self
+    }
+
     /// Adds an element to the [`Scrollable`].
     ///
     /// [`Scrollable`]: struct.Scrollable.html
@@ -105,7 +115,7 @@ impl<'a, Message, Renderer> Scrollable<'a, Message, Renderer> {
 impl<'a, Message, Renderer> Widget<Message, Renderer>
     for Scrollable<'a, Message, Renderer>
 where
-    Renderer: self::Renderer + column::Renderer,
+    Renderer: 'static + self::Renderer + column::Renderer,
 {
     fn width(&self) -> Length {
         Length::Fill
@@ -295,12 +305,13 @@ where
             is_mouse_over_scrollbar,
             scrollbar,
             offset,
+            &self.style,
             content,
         )
     }
 
     fn hash_layout(&self, state: &mut Hasher) {
-        std::any::TypeId::of::<Scrollable<'static, (), ()>>().hash(state);
+        std::any::TypeId::of::<Scrollable<'static, (), Renderer>>().hash(state);
 
         self.height.hash(state);
         self.max_height.hash(state);
@@ -447,6 +458,8 @@ pub struct Scroller {
 /// [`Scrollable`]: struct.Scrollable.html
 /// [renderer]: ../../renderer/index.html
 pub trait Renderer: crate::Renderer + Sized {
+    type Style: Default;
+
     /// Returns the [`Scrollbar`] given the bounds and content bounds of a
     /// [`Scrollable`].
     ///
@@ -483,6 +496,7 @@ pub trait Renderer: crate::Renderer + Sized {
         is_mouse_over_scrollbar: bool,
         scrollbar: Option<Scrollbar>,
         offset: u32,
+        style: &Self::Style,
         content: Self::Output,
     ) -> Self::Output;
 }
@@ -490,7 +504,7 @@ pub trait Renderer: crate::Renderer + Sized {
 impl<'a, Message, Renderer> From<Scrollable<'a, Message, Renderer>>
     for Element<'a, Message, Renderer>
 where
-    Renderer: 'a + self::Renderer + column::Renderer,
+    Renderer: 'static + self::Renderer + column::Renderer,
     Message: 'static,
 {
     fn from(
diff --git a/src/native.rs b/src/native.rs
index 67f85c20..1061a730 100644
--- a/src/native.rs
+++ b/src/native.rs
@@ -24,20 +24,6 @@ pub mod widget {
     //! [`text_input::State`]: text_input/struct.State.html
     pub use iced_wgpu::widget::*;
 
-    pub mod scrollable {
-        //! Navigate an endless amount of content with a scrollbar.
-
-        /// A widget that can vertically display an infinite amount of content
-        /// with a scrollbar.
-        ///
-        /// This is an alias of an `iced_native` scrollable with a default
-        /// `Renderer`.
-        pub type Scrollable<'a, Message> =
-            iced_winit::Scrollable<'a, Message, iced_wgpu::Renderer>;
-
-        pub use iced_winit::scrollable::State;
-    }
-
     pub mod slider {
         //! Display an interactive selector of a single value from a range of
         //! values.
diff --git a/style/src/lib.rs b/style/src/lib.rs
index 1d7e57c4..fb90b2b5 100644
--- a/style/src/lib.rs
+++ b/style/src/lib.rs
@@ -1,3 +1,4 @@
 pub mod button;
 pub mod container;
+pub mod scrollable;
 pub mod text_input;
diff --git a/style/src/scrollable.rs b/style/src/scrollable.rs
new file mode 100644
index 00000000..690c14a2
--- /dev/null
+++ b/style/src/scrollable.rs
@@ -0,0 +1,76 @@
+//! Navigate an endless amount of content with a scrollbar.
+use iced_core::{Background, Color};
+
+/// The appearance of a scrollable.
+#[derive(Debug, Clone, Copy)]
+pub struct Scrollbar {
+    pub background: Option<Background>,
+    pub border_radius: u16,
+    pub border_width: u16,
+    pub border_color: Color,
+    pub scroller: Scroller,
+}
+
+/// The appearance of the scroller of a scrollable.
+#[derive(Debug, Clone, Copy)]
+pub struct Scroller {
+    pub color: Color,
+    pub border_radius: u16,
+    pub border_width: u16,
+    pub border_color: Color,
+}
+
+/// A set of rules that dictate the style of a scrollable.
+pub trait StyleSheet {
+    /// Produces the style of an active scrollbar.
+    fn active(&self) -> Scrollbar;
+
+    /// Produces the style of an hovered scrollbar.
+    fn hovered(&self) -> Scrollbar;
+
+    /// Produces the style of a scrollbar that is being dragged.
+    fn dragging(&self) -> Scrollbar {
+        self.hovered()
+    }
+}
+
+struct Default;
+
+impl StyleSheet for Default {
+    fn active(&self) -> Scrollbar {
+        Scrollbar {
+            background: None,
+            border_radius: 5,
+            border_width: 0,
+            border_color: Color::TRANSPARENT,
+            scroller: Scroller {
+                color: [0.0, 0.0, 0.0, 0.7].into(),
+                border_radius: 5,
+                border_width: 0,
+                border_color: Color::TRANSPARENT,
+            },
+        }
+    }
+
+    fn hovered(&self) -> Scrollbar {
+        Scrollbar {
+            background: Some(Background::Color([0.0, 0.0, 0.0, 0.3].into())),
+            ..self.active()
+        }
+    }
+}
+
+impl std::default::Default for Box<dyn StyleSheet> {
+    fn default() -> Self {
+        Box::new(Default)
+    }
+}
+
+impl<T> From<T> for Box<dyn StyleSheet>
+where
+    T: 'static + StyleSheet,
+{
+    fn from(style: T) -> Self {
+        Box::new(style)
+    }
+}
diff --git a/wgpu/src/renderer/widget/scrollable.rs b/wgpu/src/renderer/widget/scrollable.rs
index 42a4a743..30d7f337 100644
--- a/wgpu/src/renderer/widget/scrollable.rs
+++ b/wgpu/src/renderer/widget/scrollable.rs
@@ -7,6 +7,8 @@ const SCROLLBAR_WIDTH: u16 = 10;
 const SCROLLBAR_MARGIN: u16 = 2;
 
 impl scrollable::Renderer for Renderer {
+    type Style = Box<dyn iced_style::scrollable::StyleSheet>;
+
     fn scrollbar(
         &self,
         bounds: Rectangle,
@@ -53,6 +55,7 @@ impl scrollable::Renderer for Renderer {
         is_mouse_over_scrollbar: bool,
         scrollbar: Option<scrollable::Scrollbar>,
         offset: u32,
+        style_sheet: &Self::Style,
         (content, mouse_cursor): Self::Output,
     ) -> Self::Output {
         let clip = Primitive::Clip {
@@ -64,17 +67,23 @@ impl scrollable::Renderer for Renderer {
         (
             if let Some(scrollbar) = scrollbar {
                 if is_mouse_over || state.is_scroller_grabbed() {
+                    let style = if state.is_scroller_grabbed() {
+                        style_sheet.dragging()
+                    } else if is_mouse_over_scrollbar {
+                        style_sheet.hovered()
+                    } else {
+                        style_sheet.active()
+                    };
+
                     let scroller = Primitive::Quad {
                         bounds: scrollbar.scroller.bounds,
-                        background: Background::Color(
-                            [0.0, 0.0, 0.0, 0.7].into(),
-                        ),
-                        border_radius: 5,
-                        border_width: 0,
-                        border_color: Color::TRANSPARENT,
+                        background: Background::Color(style.scroller.color),
+                        border_radius: style.scroller.border_radius,
+                        border_width: style.scroller.border_width,
+                        border_color: style.scroller.border_color,
                     };
 
-                    if is_mouse_over_scrollbar || state.is_scroller_grabbed() {
+                    if style.background.is_some() || style.border_width > 0 {
                         let scrollbar = Primitive::Quad {
                             bounds: Rectangle {
                                 x: scrollbar.bounds.x
@@ -83,12 +92,12 @@ impl scrollable::Renderer for Renderer {
                                     - f32::from(2 * SCROLLBAR_MARGIN),
                                 ..scrollbar.bounds
                             },
-                            background: Background::Color(
-                                [0.0, 0.0, 0.0, 0.3].into(),
+                            background: style.background.unwrap_or(
+                                Background::Color(Color::TRANSPARENT),
                             ),
-                            border_radius: 5,
-                            border_width: 0,
-                            border_color: Color::TRANSPARENT,
+                            border_radius: style.border_radius,
+                            border_width: style.border_width,
+                            border_color: style.border_color,
                         };
 
                         Primitive::Group {
diff --git a/wgpu/src/widget.rs b/wgpu/src/widget.rs
index 1d7e57c4..fb90b2b5 100644
--- a/wgpu/src/widget.rs
+++ b/wgpu/src/widget.rs
@@ -1,3 +1,4 @@
 pub mod button;
 pub mod container;
+pub mod scrollable;
 pub mod text_input;
diff --git a/wgpu/src/widget/scrollable.rs b/wgpu/src/widget/scrollable.rs
new file mode 100644
index 00000000..1d236105
--- /dev/null
+++ b/wgpu/src/widget/scrollable.rs
@@ -0,0 +1,13 @@
+//! Navigate an endless amount of content with a scrollbar.
+use crate::Renderer;
+
+pub use iced_native::scrollable::State;
+pub use iced_style::scrollable::{Scrollbar, Scroller, StyleSheet};
+
+/// A widget that can vertically display an infinite amount of content
+/// with a scrollbar.
+///
+/// This is an alias of an `iced_native` scrollable with a default
+/// `Renderer`.
+pub type Scrollable<'a, Message> =
+    iced_native::Scrollable<'a, Message, Renderer>;