Fixed some importing issues since you can use a Shader::Gradient outside a Canvas widget, where it was previously only accessible.

graphics/src/gradient.rs

@@ -1,18 +1,17 @@
 //! For creating a Gradient.
-
 use iced_native::Color;
-use crate::widget::canvas::gradient::Linear;
+use crate::gradient::linear::Linear;
+use crate::Point;
 
 #[derive(Debug, Clone, PartialEq)]
-/// A fill which transitions colors progressively along a direction, either linearly, radially,
-/// or conically.
+/// A fill which transitions colors progressively along a direction, either linearly, radially (TBD),
+/// or conically (TBD).
 pub enum Gradient {
     /// A linear gradient interpolates colors along a direction from its [`start`] to its [`end`]
     /// point.
     Linear(Linear),
 }
 
-
 #[derive(Debug, Clone, Copy, PartialEq)]
 /// A point along the gradient vector where the specified [`color`] is unmixed.
 pub struct ColorStop {
@@ -20,4 +19,85 @@ pub struct ColorStop {
     pub offset: f32,
     /// The color of the gradient at the specified [`offset`].
     pub color: Color,
-}
+}
+
+impl Gradient {
+    /// Creates a new linear [`linear::Builder`].
+    pub fn linear(start: Point, end: Point) -> linear::Builder {
+        linear::Builder::new(start, end)
+    }
+}
+
+/// Linear gradient builder & definition.
+pub mod linear {
+    use crate::gradient::{ColorStop, Gradient};
+    use crate::{Color, Point};
+
+    /// A linear gradient that can be used in the style of [`super::Fill`] or [`super::Stroke`].
+    #[derive(Debug, Clone, PartialEq)]
+    pub struct Linear {
+        /// The point where the linear gradient begins.
+        pub start: Point,
+        /// The point where the linear gradient ends.
+        pub end: Point,
+        /// [`ColorStop`]s along the linear gradient path.
+        pub color_stops: Vec<ColorStop>,
+    }
+
+    /// A [`Linear`] builder.
+    #[derive(Debug)]
+    pub struct Builder {
+        start: Point,
+        end: Point,
+        stops: Vec<(f32, Color)>,
+        valid: bool,
+    }
+
+    impl Builder {
+        /// Creates a new [`Builder`].
+        pub fn new(start: Point, end: Point) -> Self {
+            Self {
+                start,
+                end,
+                stops: vec![],
+                valid: true,
+            }
+        }
+
+        /// Adds a new stop, defined by an offset and a color, to the gradient.
+        ///
+        /// `offset` must be between `0.0` and `1.0`.
+        pub fn add_stop(mut self, offset: f32, color: Color) -> Self {
+            if !(0.0..=1.0).contains(&offset) {
+                self.valid = false;
+            }
+
+            self.stops.push((offset, color));
+            self
+        }
+
+        /// Builds the linear [`Gradient`] of this [`Builder`].
+        ///
+        /// Returns `None` if no stops were added to the builder or
+        /// if stops not between 0.0 and 1.0 were added.
+        pub fn build(self) -> Option<Gradient> {
+            if self.stops.is_empty() || !self.valid {
+                return None;
+            }
+
+            let mut stops: Vec<ColorStop> = self.stops.clone().into_iter().map(|f| ColorStop {
+                offset: f.0,
+                color: f.1
+            }).collect();
+
+            stops.sort_by(|a, b| a.offset.partial_cmp(&b.offset).unwrap());
+
+            Some(Gradient::Linear(Linear {
+                start: self.start,
+                end: self.end,
+                color_stops: stops
+            }))
+        }
+    }
+}
+