Added support for gradients as background variants + other optimizations.

1 files changed, 119 insertions, 0 deletions

diff --git a/graphics/src/gradient.rs b/graphics/src/gradient.rs
new file mode 100644
index 00000000..21bcd2c6
--- /dev/null
+++ b/graphics/src/gradient.rs
@@ -0,0 +1,119 @@
+//! A gradient that can be used as a [`Fill`] for a mesh.
+//!
+//! For a gradient that you can use as a background variant for a widget, see [`Gradient`].
+//!
+//! [`Gradient`]: crate::core::Gradient;
+use crate::core::Point;
+pub use linear::Linear;
+
+#[derive(Debug, Clone, PartialEq)]
+/// A fill which linearly interpolates colors along a direction.
+///
+/// For a gradient which can be used as a fill for a background of a widget, see [`crate::core::Gradient`].
+pub enum Gradient {
+    /// A linear gradient interpolates colors along a direction from its `start` to its `end`
+    /// point.
+    Linear(Linear),
+}
+
+impl Gradient {
+    /// Creates a new linear [`linear::Builder`].
+    ///
+    /// The `start` and `end` [`Point`]s define the absolute position of the [`Gradient`].
+    pub fn linear(start: Point, end: Point) -> linear::Builder {
+        linear::Builder::new(start, end)
+    }
+}
+
+pub mod linear {
+    //! Linear gradient builder & definition.
+    use crate::Gradient;
+    use iced_core::gradient::ColorStop;
+    use iced_core::{Color, Point};
+    use std::cmp::Ordering;
+
+    /// A linear gradient that can be used in the style of [`Fill`] or [`Stroke`].
+    ///
+    /// [`Fill`]: crate::geometry::Fill;
+    /// [`Stroke`]: crate::geometry::Stroke;
+    #[derive(Debug, Clone, Copy, PartialEq)]
+    pub struct Linear {
+        /// The absolute starting position of the gradient.
+        pub start: Point,
+
+        /// The absolute ending position of the gradient.
+        pub end: Point,
+
+        /// [`ColorStop`]s along the linear gradient direction.
+        pub color_stops: [Option<ColorStop>; 8],
+    }
+
+    /// A [`Linear`] builder.
+    #[derive(Debug)]
+    pub struct Builder {
+        start: Point,
+        end: Point,
+        stops: [Option<ColorStop>; 8],
+    }
+
+    impl Builder {
+        /// Creates a new [`Builder`].
+        pub fn new(start: Point, end: Point) -> Self {
+            Self {
+                start,
+                end,
+                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: ColorStop 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
+        }
+
+        /// Builds the linear [`Gradient`] of this [`Builder`].
+        ///
+        /// Returns `BuilderError` if gradient in invalid.
+        pub fn build(self) -> Gradient {
+            Gradient::Linear(Linear {
+                start: self.start,
+                end: self.end,
+                color_stops: self.stops,
+            })
+        }
+    }
+}