1 files changed, 105 insertions, 0 deletions
diff --git a/core/src/gradient.rs b/core/src/gradient.rs
new file mode 100644
index 00000000..e19622fb
--- /dev/null
+++ b/core/src/gradient.rs
@@ -0,0 +1,105 @@
+//! Colors that transition progressively.
+use crate::{Color, Radians};
+
+use std::cmp::Ordering;
+
+#[derive(Debug, Clone, Copy, PartialEq)]
+/// A fill which transitions colors progressively along a direction, either linearly, radially (TBD),
+/// or conically (TBD).
+///
+/// For a gradient which can be used as a fill on a canvas, see [`iced_graphics::Gradient`].
+pub enum Gradient {
+    /// A linear gradient interpolates colors along a direction at a specific [`Angle`].
+    Linear(Linear),
+}
+
+impl Gradient {
+    /// Adjust the opacity of the gradient by a multiplier applied to each color stop.
+    pub fn mul_alpha(mut self, alpha_multiplier: f32) -> Self {
+        match &mut self {
+            Gradient::Linear(linear) => {
+                for stop in linear.stops.iter_mut().flatten() {
+                    stop.color.a *= alpha_multiplier;
+                }
+            }
+        }
+
+        self
+    }
+}
+
+impl From<Linear> for Gradient {
+    fn from(gradient: Linear) -> Self {
+        Self::Linear(gradient)
+    }
+}
+
+#[derive(Debug, Default, Clone, Copy, PartialEq)]
+/// A point along the gradient vector where the specified [`color`] is unmixed.
+///
+/// [`color`]: Self::color
+pub struct ColorStop {
+    /// Offset along the gradient vector.
+    pub offset: f32,
+
+    /// The color of the gradient at the specified [`offset`].
+    ///
+    /// [`offset`]: Self::offset
+    pub color: Color,
+}
+
+/// A linear gradient.
+#[derive(Debug, Clone, Copy, PartialEq)]
+pub struct Linear {
+    /// How the [`Gradient`] is angled within its bounds.
+    pub angle: Radians,
+    /// [`ColorStop`]s along the linear gradient path.
+    pub stops: [Option<ColorStop>; 8],
+}
+
+impl Linear {
+    /// Creates a new [`Linear`] gradient with the given angle in [`Radians`].
+    pub fn new(angle: impl Into<Radians>) -> Self {
+        Self {
+            angle: angle.into(),
+            stops: [None; 8],
+        }
+    }
+
+    /// Adds a new [`ColorStop`], defined by an offset and a color, to the gradient.
+    ///
+    /// Any `offset` that is not within `0.0..=1.0` will be silently ignored.
+    ///
+    /// Any stop added after the 8th will be silently ignored.
+    pub fn add_stop(mut self, offset: f32, color: Color) -> Self {
+        if offset.is_finite() && (0.0..=1.0).contains(&offset) {
+            let (Ok(index) | Err(index)) =
+                self.stops.binary_search_by(|stop| match stop {
+                    None => Ordering::Greater,
+                    Some(stop) => stop.offset.partial_cmp(&offset).unwrap(),
+                });
+
+            if index < 8 {
+                self.stops[index] = Some(ColorStop { offset, color });
+            }
+        } else {
+            log::warn!("Gradient color stop must be within 0.0..=1.0 range.");
+        };
+
+        self
+    }
+
+    /// Adds multiple [`ColorStop`]s to the gradient.
+    ///
+    /// Any stop added after the 8th will be silently ignored.
+    pub fn add_stops(
+        mut self,
+        stops: impl IntoIterator<Item = ColorStop>,
+    ) -> Self {
+        for stop in stops.into_iter() {
+            self = self.add_stop(stop.offset, stop.color)
+        }
+
+        self
+    }
+}