Fix Sample Points node to avoid duplicating endpoints instead of closing its sampled paths (GraphiteEditor#2714)

* Skip duplicate endpoint and close sampled paths in Sample Points node
Closes GraphiteEditor#2713

* Comment

---------

Co-authored-by: Keavon Chambers <keavon@keavon.com>

Author: 2 people

node-graph/gcore/src/vector/algorithms/bezpath_algorithms.rs

@@ -1,7 +1,7 @@
 use super::poisson_disk::poisson_disk_sample;
 use crate::vector::misc::dvec2_to_point;
 use glam::DVec2;
-use kurbo::{BezPath, DEFAULT_ACCURACY, Line, ParamCurve, ParamCurveDeriv, PathSeg, Point, Rect, Shape};
+use kurbo::{BezPath, DEFAULT_ACCURACY, Line, ParamCurve, ParamCurveDeriv, PathEl, PathSeg, Point, Rect, Shape};
 
 pub fn position_on_bezpath(bezpath: &BezPath, t: f64, euclidian: bool, segments_length: Option<&[f64]>) -> Point {
 	let (segment_index, t) = t_value_to_parametric(bezpath, t, euclidian, segments_length);
@@ -21,6 +21,8 @@ pub fn tangent_on_bezpath(bezpath: &BezPath, t: f64, euclidian: bool, segments_l
 pub fn sample_points_on_bezpath(bezpath: BezPath, spacing: f64, start_offset: f64, stop_offset: f64, adaptive_spacing: bool, segments_length: &[f64]) -> Option<BezPath> {
 	let mut sample_bezpath = BezPath::new();
 
+	let was_closed = matches!(bezpath.elements().last(), Some(PathEl::ClosePath));
+
 	// Calculate the total length of the collected segments.
 	let total_length: f64 = segments_length.iter().sum();
 
@@ -50,11 +52,15 @@ pub fn sample_points_on_bezpath(bezpath: BezPath, spacing: f64, start_offset: f6
 		return None;
 	}
 
+	// Decide how many loop-iterations: if closed, skip the last duplicate point
+	let sample_count_usize = sample_count as usize;
+	let max_i = if was_closed { sample_count_usize } else { sample_count_usize + 1 };
+
 	// Generate points along the path based on calculated intervals.
 	let mut length_up_to_previous_segment = 0.;
 	let mut next_segment_index = 0;
 
-	for count in 0..=sample_count as usize {
+	for count in 0..max_i {
 		let fraction = count as f64 / sample_count;
 		let length_up_to_next_sample_point = fraction * used_length + start_offset;
 		let mut next_length = length_up_to_next_sample_point - length_up_to_previous_segment;
@@ -84,6 +90,10 @@ pub fn sample_points_on_bezpath(bezpath: BezPath, spacing: f64, start_offset: f6
 		}
 	}
 
+	if was_closed {
+		sample_bezpath.close_path();
+	}
+
 	Some(sample_bezpath)
 }