Added support for gradients as background variants + other optimizations.

6 files changed, 144 insertions, 16 deletions

diff --git a/graphics/src/geometry/fill.rs b/graphics/src/geometry/fill.rs
index 2e8c1669..6aa1f28b 100644
--- a/graphics/src/geometry/fill.rs
+++ b/graphics/src/geometry/fill.rs
@@ -1,7 +1,8 @@
 //! Fill [crate::widget::canvas::Geometry] with a certain style.
-use iced_core::{Color, Gradient};
+use iced_core::Color;
 
 pub use crate::geometry::Style;
+use crate::Gradient;
 
 /// The style used to fill geometry.
 #[derive(Debug, Clone)]
diff --git a/graphics/src/geometry/style.rs b/graphics/src/geometry/style.rs
index be9ee376..ece6b32a 100644
--- a/graphics/src/geometry/style.rs
+++ b/graphics/src/geometry/style.rs
@@ -1,4 +1,5 @@
-use iced_core::{Color, Gradient};
+use crate::Gradient;
+use iced_core::Color;
 
 /// The coloring style of some drawing.
 #[derive(Debug, Clone, PartialEq)]
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,
+            })
+        }
+    }
+}
diff --git a/graphics/src/lib.rs b/graphics/src/lib.rs
index 91f50282..ae338936 100644
--- a/graphics/src/lib.rs
+++ b/graphics/src/lib.rs
@@ -23,6 +23,7 @@
 #![cfg_attr(docsrs, feature(doc_cfg))]
 mod antialiasing;
 mod error;
+mod gradient;
 mod transformation;
 mod viewport;
 
@@ -42,6 +43,7 @@ pub use antialiasing::Antialiasing;
 pub use backend::Backend;
 pub use compositor::Compositor;
 pub use error::Error;
+pub use gradient::Gradient;
 pub use primitive::Primitive;
 pub use renderer::Renderer;
 pub use transformation::Transformation;
diff --git a/graphics/src/primitive.rs b/graphics/src/primitive.rs
index d4446c87..9728db39 100644
--- a/graphics/src/primitive.rs
+++ b/graphics/src/primitive.rs
@@ -3,7 +3,7 @@ use crate::core::alignment;
 use crate::core::image;
 use crate::core::svg;
 use crate::core::text;
-use crate::core::{Background, Color, Font, Gradient, Rectangle, Size, Vector};
+use crate::core::{Background, Color, Font, Rectangle, Size, Vector};
 
 use bytemuck::{Pod, Zeroable};
 use std::sync::Arc;
@@ -39,7 +39,7 @@ pub enum Primitive {
         bounds: Rectangle,
         /// The background of the quad
         background: Background,
-        /// The border radius of the quad
+        /// The border radii of the quad
         border_radius: [f32; 4],
         /// The border width of the quad
         border_width: f32,
@@ -81,15 +81,12 @@ pub enum Primitive {
     /// It can be used to render many kinds of geometry freely.
     GradientMesh {
         /// The vertices and indices of the mesh.
-        buffers: Mesh2D<Vertex2D>,
+        buffers: Mesh2D<GradientVertex2D>,
 
         /// The size of the drawable region of the mesh.
         ///
         /// Any geometry that falls out of this region will be clipped.
         size: Size,
-
-        /// The [`Gradient`] to apply to the mesh.
-        gradient: Gradient,
     },
     /// A [`tiny_skia`] path filled with some paint.
     #[cfg(feature = "tiny-skia")]
@@ -242,25 +239,34 @@ pub struct Mesh2D<T> {
     pub indices: Vec<u32>,
 }
 
-/// A two-dimensional vertex.
+/// A two-dimensional vertex with a color.
 #[derive(Copy, Clone, Debug, PartialEq, Zeroable, Pod)]
 #[repr(C)]
-pub struct Vertex2D {
+pub struct ColoredVertex2D {
     /// The vertex position in 2D space.
     pub position: [f32; 2],
+
+    /// The color of the vertex in __linear__ RGBA.
+    pub color: [f32; 4],
 }
 
-/// A two-dimensional vertex with a color.
-#[derive(Copy, Clone, Debug, PartialEq, Zeroable, Pod)]
+/// A vertex which contains 2D position & packed gradient data.
+#[derive(Copy, Clone, Debug, PartialEq)]
 #[repr(C)]
-pub struct ColoredVertex2D {
+pub struct GradientVertex2D {
     /// The vertex position in 2D space.
     pub position: [f32; 2],
 
-    /// The color of the vertex in __linear__ RGBA.
-    pub color: [f32; 4],
+    /// The packed vertex data of the gradient.
+    pub gradient: [f32; 44],
 }
 
+#[allow(unsafe_code)]
+unsafe impl Zeroable for GradientVertex2D {}
+
+#[allow(unsafe_code)]
+unsafe impl Pod for GradientVertex2D {}
+
 impl From<()> for Primitive {
     fn from(_: ()) -> Self {
         Self::Group { primitives: vec![] }
diff --git a/graphics/src/triangle.rs b/graphics/src/triangle.rs
deleted file mode 100644
index 09b61767..00000000
--- a/graphics/src/triangle.rs
+++ /dev/null
@@ -1 +0,0 @@
-//! Draw geometry using meshes of triangles.