From 29b1220ec33da3573eb0dc6492cafc417b2ebf39 Mon Sep 17 00:00:00 2001
From: Ben Cragg <bcvery1@gmail.com>
Date: Thu, 4 Apr 2019 15:48:27 +0100
Subject: [PATCH] Setting order of returned points on Rect

---
 geometry.go      |  8 +++++++-
 geometry_test.go | 20 ++------------------
 2 files changed, 9 insertions(+), 19 deletions(-)

diff --git a/geometry.go b/geometry.go
index b332f25..9b232bf 100644
--- a/geometry.go
+++ b/geometry.go
@@ -3,6 +3,7 @@ package pixel
 import (
 	"fmt"
 	"math"
+	"sort"
 )
 
 // Clamp returns x clamped to the interval [min, max].
@@ -610,7 +611,8 @@ func (r Rect) IntersectLine(l Line) Vec {
 }
 
 // IntersectionPoints returns all the points where the Rect intersects with the line provided.  This can be zero, one or
-// two points, depending on the location of the shapes.
+// two points, depending on the location of the shapes.  The points of intersection will be returned in order of
+// closest-to-l.A to closest-to-l.B.
 func (r Rect) IntersectionPoints(l Line) []Vec {
 	// Use map keys to ensure unique points
 	pointMap := make(map[Vec]struct{})
@@ -625,6 +627,10 @@ func (r Rect) IntersectionPoints(l Line) []Vec {
 	for point := range pointMap {
 		points = append(points, point)
 	}
+
+	// Order the points
+	sort.Slice(points, func(i, j int) bool { return points[i].To(l.A).Len() < points[j].To(l.A).Len() })
+
 	return points
 }
 
diff --git a/geometry_test.go b/geometry_test.go
index ebabfa0..2f214a7 100644
--- a/geometry_test.go
+++ b/geometry_test.go
@@ -839,16 +839,6 @@ func TestRect_IntersectCircle(t *testing.T) {
 }
 
 func TestRect_IntersectionPoints(t *testing.T) {
-	in := func(v pixel.Vec, vs []pixel.Vec) bool {
-		for _, vec := range vs {
-			if vec == v {
-				return true
-			}
-		}
-
-		return false
-	}
-
 	type fields struct {
 		Min pixel.Vec
 		Max pixel.Vec
@@ -887,14 +877,8 @@ func TestRect_IntersectionPoints(t *testing.T) {
 				Min: tt.fields.Min,
 				Max: tt.fields.Max,
 			}
-			got := r.IntersectionPoints(tt.args.l)
-			if len(got) != len(tt.want) {
-				t.Errorf("Rect.IntersectPoints() has incorrect length.  Expected %d, got %d", len(tt.want), len(got))
-			}
-			for _, v := range got {
-				if !in(v, tt.want) {
-					t.Errorf("Rect.IntersectPoints(): got unexpected result = %v", v)
-				}
+			if got := r.IntersectionPoints(tt.args.l); !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("Rect.IntersectPoints() = %v, want %v", got, tt.want)
 			}
 		})
 	}