Implement `Canvas` support for `iced_tiny_skia`

1 files changed, 192 insertions, 0 deletions

diff --git a/native/src/widget/canvas/path/builder.rs b/native/src/widget/canvas/path/builder.rs
new file mode 100644
index 00000000..84fda052
--- /dev/null
+++ b/native/src/widget/canvas/path/builder.rs
@@ -0,0 +1,192 @@
+use crate::widget::canvas::path::{arc, Arc, Path};
+use crate::{Point, Size};
+
+use lyon_path::builder::{self, SvgPathBuilder};
+use lyon_path::geom;
+use lyon_path::math;
+
+/// A [`Path`] builder.
+///
+/// Once a [`Path`] is built, it can no longer be mutated.
+#[allow(missing_debug_implementations)]
+pub struct Builder {
+    raw: builder::WithSvg<lyon_path::path::BuilderImpl>,
+}
+
+impl Builder {
+    /// Creates a new [`Builder`].
+    pub fn new() -> Builder {
+        Builder {
+            raw: lyon_path::Path::builder().with_svg(),
+        }
+    }
+
+    /// Moves the starting point of a new sub-path to the given `Point`.
+    #[inline]
+    pub fn move_to(&mut self, point: Point) {
+        let _ = self.raw.move_to(math::Point::new(point.x, point.y));
+    }
+
+    /// Connects the last point in the [`Path`] to the given `Point` with a
+    /// straight line.
+    #[inline]
+    pub fn line_to(&mut self, point: Point) {
+        let _ = self.raw.line_to(math::Point::new(point.x, point.y));
+    }
+
+    /// Adds an [`Arc`] to the [`Path`] from `start_angle` to `end_angle` in
+    /// a clockwise direction.
+    #[inline]
+    pub fn arc(&mut self, arc: Arc) {
+        self.ellipse(arc.into());
+    }
+
+    /// Adds a circular arc to the [`Path`] with the given control points and
+    /// radius.
+    ///
+    /// This essentially draws a straight line segment from the current
+    /// position to `a`, but fits a circular arc of `radius` tangent to that
+    /// segment and tangent to the line between `a` and `b`.
+    ///
+    /// With another `.line_to(b)`, the result will be a path connecting the
+    /// starting point and `b` with straight line segments towards `a` and a
+    /// circular arc smoothing out the corner at `a`.
+    ///
+    /// See [the HTML5 specification of `arcTo`](https://html.spec.whatwg.org/multipage/canvas.html#building-paths:dom-context-2d-arcto)
+    /// for more details and examples.
+    pub fn arc_to(&mut self, a: Point, b: Point, radius: f32) {
+        let start = self.raw.current_position();
+        let mid = math::Point::new(a.x, a.y);
+        let end = math::Point::new(b.x, b.y);
+
+        if start == mid || mid == end || radius == 0.0 {
+            let _ = self.raw.line_to(mid);
+            return;
+        }
+
+        let double_area = start.x * (mid.y - end.y)
+            + mid.x * (end.y - start.y)
+            + end.x * (start.y - mid.y);
+
+        if double_area == 0.0 {
+            let _ = self.raw.line_to(mid);
+            return;
+        }
+
+        let to_start = (start - mid).normalize();
+        let to_end = (end - mid).normalize();
+
+        let inner_angle = to_start.dot(to_end).acos();
+
+        let origin_angle = inner_angle / 2.0;
+
+        let origin_adjacent = radius / origin_angle.tan();
+
+        let arc_start = mid + to_start * origin_adjacent;
+        let arc_end = mid + to_end * origin_adjacent;
+
+        let sweep = to_start.cross(to_end) < 0.0;
+
+        let _ = self.raw.line_to(arc_start);
+
+        self.raw.arc_to(
+            math::Vector::new(radius, radius),
+            math::Angle::radians(0.0),
+            lyon_path::ArcFlags {
+                large_arc: false,
+                sweep,
+            },
+            arc_end,
+        );
+    }
+
+    /// Adds an ellipse to the [`Path`] using a clockwise direction.
+    pub fn ellipse(&mut self, arc: arc::Elliptical) {
+        let arc = geom::Arc {
+            center: math::Point::new(arc.center.x, arc.center.y),
+            radii: math::Vector::new(arc.radii.x, arc.radii.y),
+            x_rotation: math::Angle::radians(arc.rotation),
+            start_angle: math::Angle::radians(arc.start_angle),
+            sweep_angle: math::Angle::radians(arc.end_angle - arc.start_angle),
+        };
+
+        let _ = self.raw.move_to(arc.sample(0.0));
+
+        arc.for_each_quadratic_bezier(&mut |curve| {
+            let _ = self.raw.quadratic_bezier_to(curve.ctrl, curve.to);
+        });
+    }
+
+    /// Adds a cubic Bézier curve to the [`Path`] given its two control points
+    /// and its end point.
+    #[inline]
+    pub fn bezier_curve_to(
+        &mut self,
+        control_a: Point,
+        control_b: Point,
+        to: Point,
+    ) {
+        let _ = self.raw.cubic_bezier_to(
+            math::Point::new(control_a.x, control_a.y),
+            math::Point::new(control_b.x, control_b.y),
+            math::Point::new(to.x, to.y),
+        );
+    }
+
+    /// Adds a quadratic Bézier curve to the [`Path`] given its control point
+    /// and its end point.
+    #[inline]
+    pub fn quadratic_curve_to(&mut self, control: Point, to: Point) {
+        let _ = self.raw.quadratic_bezier_to(
+            math::Point::new(control.x, control.y),
+            math::Point::new(to.x, to.y),
+        );
+    }
+
+    /// Adds a rectangle to the [`Path`] given its top-left corner coordinate
+    /// and its `Size`.
+    #[inline]
+    pub fn rectangle(&mut self, top_left: Point, size: Size) {
+        self.move_to(top_left);
+        self.line_to(Point::new(top_left.x + size.width, top_left.y));
+        self.line_to(Point::new(
+            top_left.x + size.width,
+            top_left.y + size.height,
+        ));
+        self.line_to(Point::new(top_left.x, top_left.y + size.height));
+        self.close();
+    }
+
+    /// Adds a circle to the [`Path`] given its center coordinate and its
+    /// radius.
+    #[inline]
+    pub fn circle(&mut self, center: Point, radius: f32) {
+        self.arc(Arc {
+            center,
+            radius,
+            start_angle: 0.0,
+            end_angle: 2.0 * std::f32::consts::PI,
+        });
+    }
+
+    /// Closes the current sub-path in the [`Path`] with a straight line to
+    /// the starting point.
+    #[inline]
+    pub fn close(&mut self) {
+        self.raw.close()
+    }
+
+    /// Builds the [`Path`] of this [`Builder`].
+    #[inline]
+    pub fn build(self) -> Path {
+        Path {
+            raw: self.raw.build(),
+        }
+    }
+}
+
+impl Default for Builder {
+    fn default() -> Self {
+        Self::new()
+    }
+}