feat!(widget): rewrite button & icon widget APIs

src/widget/button/style.rs

@@ -0,0 +1,90 @@
+// Copyright 2023 System76 <info@system76.com>
+// SPDX-License-Identifier: MPL-2.0
+
+//! Change the apperance of a button.
+use iced_core::{Background, BorderRadius, Color, Vector};
+
+/// The appearance of a button.
+#[must_use]
+#[derive(Debug, Clone, Copy)]
+pub struct Appearance {
+    /// The amount of offset to apply to the shadow of the button.
+    pub shadow_offset: Vector,
+
+    /// The [`Background`] of the button.
+    pub background: Option<Background>,
+
+    /// The border radius of the button.
+    pub border_radius: BorderRadius,
+
+    /// The border width of the button.
+    pub border_width: f32,
+
+    /// The border [`Color`] of the button.
+    pub border_color: Color,
+
+    /// Opacity of the button.
+    pub opacity: f32,
+
+    /// An outline placed around the border.
+    pub outline_width: f32,
+
+    /// The [`Color`] of the outline.
+    pub outline_color: Color,
+
+    /// The icon [`Color`] of the button.
+    pub icon_color: Option<Color>,
+
+    /// The text [`Color`] of the button.
+    pub text_color: Color,
+}
+
+impl Appearance {
+    // TODO: `BorderRadius` is not `const fn` compatible.
+    pub fn new() -> Self {
+        Self {
+            shadow_offset: Vector::new(0.0, 0.0),
+            background: None,
+            border_radius: BorderRadius::from(0.0),
+            border_width: 0.0,
+            border_color: Color::TRANSPARENT,
+            opacity: 1.0,
+            outline_width: 0.0,
+            outline_color: Color::TRANSPARENT,
+            icon_color: None,
+            text_color: Color::BLACK,
+        }
+    }
+}
+
+impl std::default::Default for Appearance {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+/// A set of rules that dictate the style of a button.
+pub trait StyleSheet {
+    /// The supported style of the [`StyleSheet`].
+    type Style: Default;
+
+    /// Produces the active [`Appearance`] of a button.
+    fn active(&self, focused: bool, style: &Self::Style) -> Appearance;
+
+    /// Produces the disabled [`Appearance`] of a button.
+    fn disabled(&self, style: &Self::Style) -> Appearance;
+
+    /// [`Appearance`] when the button is the target of a DND operation.
+    fn drop_target(&self, style: &Self::Style) -> Appearance {
+        self.hovered(false, style)
+    }
+
+    /// Produces the hovered [`Appearance`] of a button.
+    fn hovered(&self, focused: bool, style: &Self::Style) -> Appearance;
+
+    /// Produces the pressed [`Appearance`] of a button.
+    fn pressed(&self, focused: bool, style: &Self::Style) -> Appearance;
+
+    /// [`Appearance`] when a button is selected.
+    fn selected(&self, focused: bool, style: &Self::Style) -> Appearance;
+}