Introduce fill rule setting in canvas

graphics/src/widget/canvas/fill.rs

@@ -2,19 +2,59 @@ use iced_native::Color;
 
 /// The style used to fill geometry.
 #[derive(Debug, Clone, Copy)]
-pub enum Fill {
-    /// Fill with a color.
-    Color(Color),
+pub struct Fill {
+    /// The color used to fill geometry.
+    ///
+    /// By default, it is set to `BLACK`.
+    pub color: Color,
+
+    /// The fill rule defines how to determine what is inside and what is
+    /// outside of a shape.
+    ///
+    /// See the [SVG specification][1] for more details.
+    ///
+    /// By default, it is set to `NonZero`.
+    ///
+    /// [1]: https://www.w3.org/TR/SVG/painting.html#FillRuleProperty
+    pub rule: FillRule,
 }
 
 impl Default for Fill {
     fn default() -> Fill {
-        Fill::Color(Color::BLACK)
+        Fill {
+            color: Color::BLACK,
+            rule: FillRule::NonZero,
+        }
     }
 }
 
 impl From<Color> for Fill {
     fn from(color: Color) -> Fill {
-        Fill::Color(color)
+        Fill {
+            color,
+            ..Fill::default()
+        }
+    }
+}
+
+/// The fill rule defines how to determine what is inside and what is outside of
+/// a shape.
+///
+/// See the [SVG specification][1].
+///
+/// [1]: https://www.w3.org/TR/SVG/painting.html#FillRuleProperty
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+#[allow(missing_docs)]
+pub enum FillRule {
+    NonZero,
+    EvenOdd,
+}
+
+impl From<FillRule> for lyon::tessellation::FillRule {
+    fn from(rule: FillRule) -> lyon::tessellation::FillRule {
+        match rule {
+            FillRule::NonZero => lyon::tessellation::FillRule::NonZero,
+            FillRule::EvenOdd => lyon::tessellation::FillRule::EvenOdd,
+        }
     }
 }