Add line dash API

graphics/src/widget/canvas/path.rs

@@ -7,7 +7,11 @@ mod builder;
 pub use arc::Arc;
 pub use builder::Builder;
 
+use crate::canvas::LineDash;
+
 use iced_native::{Point, Size};
+use lyon::path::iterator::PathIterator;
+use lyon_algorithms::walk::{walk_along_path, RepeatedPattern};
 
 /// An immutable set of points that may or may not be connected.
 ///
@@ -66,3 +70,43 @@ impl Path {
         }
     }
 }
+
+pub(super) fn dashed(path: &Path, line_dash: LineDash) -> Path {
+    let segments_odd = line_dash.segments.len() % 2 == 1;
+
+    let segments = segments_odd
+        .then(|| [&line_dash.segments[..], &line_dash.segments[..]].concat())
+        .unwrap_or(line_dash.segments);
+
+    let mut points = vec![];
+
+    walk_along_path(
+        path.raw().iter().flattened(0.01),
+        0.0,
+        &mut RepeatedPattern {
+            callback: |position: lyon_algorithms::math::Point,
+                       _tangent,
+                       _distance| {
+                points.push(Point {
+                    x: position.x,
+                    y: position.y,
+                });
+                true
+            },
+            index: line_dash.offset,
+            intervals: &segments,
+        },
+    );
+
+    Path::new(|builder| {
+        for (idx, point) in points.into_iter().enumerate() {
+            let is_even = idx % 2 == 0;
+
+            if is_even {
+                builder.move_to(point);
+            } else {
+                builder.line_to(point);
+            }
+        }
+    })
+}