Add Area and Centroid nodes (#1749)

* initial attempt for area node

* allow node preview for more types

* make AreaNode sync and add CentroidNode

* cargo fmt

* preview of DVec2

* make the nodes async again

* use segment domain instead of region domain

* modify the check for linearity

* create a limit for area in centroid calculation

* cargo fmt

* reverse unnecessary changes

* add threshold to area calculation too.

* handle zero area edge case

* add todo comment

* implement 1D centroid and use it as fallback

* formatting floats to skip last zero

* add Centroid Type radio button to Centroid Node

* rename docs to use area and perimeter centroid

* add web demos for perimeter centroid

* add tests for perimeter centroid

* add fallback to use average of points

* Fix for broken area

* missing fixes

* Code review and rename Perimeter Centroid to Length Centroid

* Use dummy footprint in Area and Centroid nodes

* add doc and todo to clarify when `is_linear` fails

* use epsilon instead of zero

---------

Co-authored-by: 0hypercube <0hypercube@gmail.com>
Co-authored-by: Keavon Chambers <keavon@keavon.com>
Co-authored-by: Dennis Kobert <dennis@kobert.dev>

libraries/bezier-rs/src/bezier/core.rs

@@ -218,6 +218,19 @@ impl Bezier {
 
 		self.get_points().all(|point| point.abs_diff_eq(start, MAX_ABSOLUTE_DIFFERENCE))
 	}
+
+	/// Returns true if the Bezier curve is equivalent to a line.
+	///
+	/// **NOTE**: This is different from simply checking if the handle is [`BezierHandles::Linear`]. A [`Quadratic`](BezierHandles::Quadratic) or [`Cubic`](BezierHandles::Cubic) Bezier curve can also be a line if the handles are colinear to the start and end points. Therefore if the handles exceed the start and end point, it will still be considered as a line.
+	pub fn is_linear(&self) -> bool {
+		let is_colinear = |a: DVec2, b: DVec2, c: DVec2| -> bool { ((b.x - a.x) * (c.y - a.y) - (b.y - a.y) * (c.x - a.x)).abs() < MAX_ABSOLUTE_DIFFERENCE };
+
+		match self.handles {
+			BezierHandles::Linear => true,
+			BezierHandles::Quadratic { handle } => is_colinear(self.start, handle, self.end),
+			BezierHandles::Cubic { handle_start, handle_end } => is_colinear(self.start, handle_start, self.end) && is_colinear(self.start, handle_end, self.end),
+		}
+	}
 }
 
 #[cfg(test)]