From 857e6c4e478403ee286bee6d691ab3d18ca91d55 Mon Sep 17 00:00:00 2001
From: Thomas Friedel <tomee6@gmail.com>
Date: Wed, 17 Apr 2019 11:31:53 +0200
Subject: [PATCH] IsPointInStroke implemented

---
 canvas.go |  6 ++++++
 path2d.go | 27 +++++++++++++++++++++++++--
 paths.go  | 30 +++++++++++++++++++-----------
 3 files changed, 50 insertions(+), 13 deletions(-)

diff --git a/canvas.go b/canvas.go
index e0e8894..94cf189 100644
--- a/canvas.go
+++ b/canvas.go
@@ -460,3 +460,9 @@ func (cv *Canvas) SetShadowBlur(r float64) {
 func (cv *Canvas) IsPointInPath(x, y float64, rule pathRule) bool {
 	return cv.path.IsPointInPath(x, y, rule)
 }
+
+// IsPointInStroke returns true if the point is in the current
+// path stroke
+func (cv *Canvas) IsPointInStroke(x, y float64) bool {
+	return cv.path.IsPointInStroke(x, y)
+}
diff --git a/path2d.go b/path2d.go
index 1b3a26b..49e4668 100644
--- a/path2d.go
+++ b/path2d.go
@@ -5,6 +5,7 @@ import (
 )
 
 type Path2D struct {
+	cv    *Canvas
 	p     []pathPoint
 	move  vec
 	cwSum float64
@@ -28,8 +29,8 @@ const (
 )
 
 // NewPath2D creates a new Path2D and returns it
-func NewPath2D() *Path2D {
-	return &Path2D{p: make([]pathPoint, 0, 20)}
+func (cv *Canvas) NewPath2D() *Path2D {
+	return &Path2D{cv: cv, p: make([]pathPoint, 0, 20)}
 }
 
 // func (p *Path2D) AddPath(p2 *Path2D) {
@@ -344,3 +345,25 @@ func (p *Path2D) IsPointInPath(x, y float64, rule pathRule) bool {
 	})
 	return inside
 }
+
+// IsPointInStroke returns true if the point is in the stroke
+func (p *Path2D) IsPointInStroke(x, y float64) bool {
+	if len(p.p) == 0 {
+		return false
+	}
+
+	var triBuf [500][2]float64
+	tris := p.cv.strokeTris(p, mat{}, false, triBuf[:0])
+
+	pt := vec{x, y}
+
+	for i := 0; i < len(tris); i += 3 {
+		a := vec{tris[i][0], tris[i][1]}
+		b := vec{tris[i+1][0], tris[i+1][1]}
+		c := vec{tris[i+2][0], tris[i+2][1]}
+		if triangleContainsPoint(a, b, c, pt) {
+			return true
+		}
+	}
+	return false
+}
diff --git a/paths.go b/paths.go
index a3be3d4..7570951 100644
--- a/paths.go
+++ b/paths.go
@@ -92,6 +92,20 @@ func (cv *Canvas) strokePath(path *Path2D, inv mat, doInv bool) {
 		return
 	}
 
+	var triBuf [500][2]float64
+	tris := cv.strokeTris(path, inv, doInv, triBuf[:0])
+
+	cv.drawShadow2(tris, nil)
+
+	stl := cv.backendFillStyle(&cv.state.stroke, 1)
+	cv.b.Fill(&stl, tris)
+}
+
+func (cv *Canvas) strokeTris(path *Path2D, inv mat, doInv bool, target [][2]float64) [][2]float64 {
+	if len(path.p) == 0 {
+		return target
+	}
+
 	if doInv {
 		for i, pt := range path.p {
 			path.p[i].pos = pt.pos.mulMat(inv)
@@ -101,9 +115,6 @@ func (cv *Canvas) strokePath(path *Path2D, inv mat, doInv bool) {
 
 	dashedPath := cv.applyLineDash(path.p)
 
-	var triBuf [500][2]float64
-	tris := triBuf[:0]
-
 	start := true
 	var p0 vec
 	for _, p := range dashedPath {
@@ -131,7 +142,7 @@ func (cv *Canvas) strokePath(path *Path2D, inv mat, doInv bool) {
 				lp0 = lp0.sub(v0)
 				lp2 = lp2.sub(v0)
 			case Round:
-				tris = cv.addCircleTris(p0, cv.state.lineWidth*0.5, tris)
+				target = cv.addCircleTris(p0, cv.state.lineWidth*0.5, target)
 			}
 		}
 
@@ -143,24 +154,21 @@ func (cv *Canvas) strokePath(path *Path2D, inv mat, doInv bool) {
 				lp1 = lp1.add(v0)
 				lp3 = lp3.add(v0)
 			case Round:
-				tris = cv.addCircleTris(p1, cv.state.lineWidth*0.5, tris)
+				target = cv.addCircleTris(p1, cv.state.lineWidth*0.5, target)
 			}
 		}
 
-		tris = append(tris, cv.tf(lp0), cv.tf(lp1), cv.tf(lp3), cv.tf(lp0), cv.tf(lp3), cv.tf(lp2))
+		target = append(target, cv.tf(lp0), cv.tf(lp1), cv.tf(lp3), cv.tf(lp0), cv.tf(lp3), cv.tf(lp2))
 
 		if p.flags&pathAttach != 0 && cv.state.lineWidth > 1 {
-			tris = cv.lineJoint(p0, p1, p.next, lp0, lp1, lp2, lp3, tris)
+			target = cv.lineJoint(p0, p1, p.next, lp0, lp1, lp2, lp3, target)
 		}
 
 		p0 = p1
 		start = false
 	}
 
-	cv.drawShadow2(tris, nil)
-
-	stl := cv.backendFillStyle(&cv.state.stroke, 1)
-	cv.b.Fill(&stl, tris)
+	return target
 }
 
 func (cv *Canvas) applyLineDash(path []pathPoint) []pathPoint {