From ff4c73b6b7929766b86d0bd72fd898c3ff7ad09e Mon Sep 17 00:00:00 2001
From: Thomas Friedel <tomee6@gmail.com>
Date: Wed, 17 Apr 2019 11:50:33 +0200
Subject: [PATCH] fixed a transformation issue

---
 canvas.go        | 22 ++++++++++++++++++++--
 canvas_test.go   |  2 +-
 paths.go         | 25 +++++++++++++++----------
 triangulation.go |  4 ++--
 4 files changed, 38 insertions(+), 15 deletions(-)

diff --git a/canvas.go b/canvas.go
index 94cf189..4bd68b2 100644
--- a/canvas.go
+++ b/canvas.go
@@ -142,6 +142,7 @@ func New(backend backendbase.Backend) *Canvas {
 	cv.state.fill.color = color.RGBA{A: 255}
 	cv.state.stroke.color = color.RGBA{A: 255}
 	cv.state.transform = matIdentity()
+	cv.path.cv = cv
 	return cv
 }
 
@@ -393,7 +394,7 @@ func (cv *Canvas) Restore() {
 	cv.b.ClearClip()
 	for _, st := range cv.stateStack {
 		if len(st.clip.p) > 0 {
-			cv.clip(&st.clip)
+			cv.clip(&st.clip, matIdentity())
 		}
 	}
 	cv.state = cv.stateStack[l-1]
@@ -464,5 +465,22 @@ func (cv *Canvas) IsPointInPath(x, y float64, rule pathRule) bool {
 // 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)
+	if len(cv.path.p) == 0 {
+		return false
+	}
+
+	var triBuf [500][2]float64
+	tris := cv.strokeTris(&cv.path, cv.state.transform.invert(), true, 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/canvas_test.go b/canvas_test.go
index 6c3219f..82323f1 100644
--- a/canvas_test.go
+++ b/canvas_test.go
@@ -473,7 +473,7 @@ func TestConvexSelfIntersecting(t *testing.T) {
 
 func TestTransform(t *testing.T) {
 	run(t, func(cv *canvas.Canvas) {
-		path := canvas.NewPath2D()
+		path := cv.NewPath2D()
 		path.MoveTo(-10, -10)
 		path.LineTo(10, -10)
 		path.LineTo(0, 10)
diff --git a/paths.go b/paths.go
index 7570951..a411027 100644
--- a/paths.go
+++ b/paths.go
@@ -336,11 +336,16 @@ func lineIntersection(a0, a1, b0, b1 vec) (vec, float64, float64) {
 
 // Fill fills the current path with the current FillStyle
 func (cv *Canvas) Fill() {
-	cv.FillPath(&cv.path)
+	cv.fillPath(&cv.path, matIdentity())
 }
 
 // FillPath fills the given path with the current FillStyle
 func (cv *Canvas) FillPath(path *Path2D) {
+	cv.fillPath(path, cv.state.transform)
+}
+
+// FillPath fills the given path with the current FillStyle
+func (cv *Canvas) fillPath(path *Path2D, tf mat) {
 	if len(path.p) < 3 {
 		return
 	}
@@ -348,7 +353,7 @@ func (cv *Canvas) FillPath(path *Path2D) {
 	var triBuf [500][2]float64
 	tris := triBuf[:0]
 	runSubPaths(path.p, func(sp []pathPoint) bool {
-		tris = appendSubPathTriangles(tris, sp)
+		tris = appendSubPathTriangles(tris, tf, sp)
 		return false
 	})
 	if len(tris) == 0 {
@@ -361,23 +366,23 @@ func (cv *Canvas) FillPath(path *Path2D) {
 	cv.b.Fill(&stl, tris)
 }
 
-func appendSubPathTriangles(tris [][2]float64, path []pathPoint) [][2]float64 {
+func appendSubPathTriangles(tris [][2]float64, mat mat, path []pathPoint) [][2]float64 {
 	last := path[len(path)-1]
 	if last.flags&pathIsConvex != 0 {
-		p0, p1 := path[0].pos, path[1].pos
+		p0, p1 := path[0].pos.mulMat(mat), path[1].pos.mulMat(mat)
 		last := len(path)
 		for i := 2; i < last; i++ {
-			p2 := path[i].pos
+			p2 := path[i].pos.mulMat(mat)
 			tris = append(tris, p0, p1, p2)
 			p1 = p2
 		}
 	} else if last.flags&pathSelfIntersects != 0 {
 		selfIntersectingPathParts(path, func(sp []pathPoint) bool {
-			tris = triangulatePath(sp, tris)
+			tris = triangulatePath(sp, mat, tris)
 			return false
 		})
 	} else {
-		tris = triangulatePath(path, tris)
+		tris = triangulatePath(path, mat, tris)
 	}
 	return tris
 }
@@ -385,10 +390,10 @@ func appendSubPathTriangles(tris [][2]float64, path []pathPoint) [][2]float64 {
 // Clip uses the current path to clip any further drawing. Use Save/Restore to
 // remove the clipping again
 func (cv *Canvas) Clip() {
-	cv.clip(&cv.path)
+	cv.clip(&cv.path, matIdentity())
 }
 
-func (cv *Canvas) clip(path *Path2D) {
+func (cv *Canvas) clip(path *Path2D, tf mat) {
 	if len(path.p) < 3 {
 		return
 	}
@@ -396,7 +401,7 @@ func (cv *Canvas) clip(path *Path2D) {
 	var triBuf [500][2]float64
 	tris := triBuf[:0]
 	runSubPaths(path.p, func(sp []pathPoint) bool {
-		tris = appendSubPathTriangles(tris, sp)
+		tris = appendSubPathTriangles(tris, tf, sp)
 		return false
 	})
 	if len(tris) == 0 {
diff --git a/triangulation.go b/triangulation.go
index f3ae316..7c1763b 100644
--- a/triangulation.go
+++ b/triangulation.go
@@ -84,11 +84,11 @@ func polygonContainsPoint(polygon []vec, p vec) bool {
 	return count%2 == 1
 }
 
-func triangulatePath(path []pathPoint, target [][2]float64) [][2]float64 {
+func triangulatePath(path []pathPoint, mat mat, target [][2]float64) [][2]float64 {
 	var buf [500]vec
 	polygon := buf[:0]
 	for _, p := range path {
-		polygon = append(polygon, p.pos)
+		polygon = append(polygon, p.pos.mulMat(mat))
 	}
 
 	for len(polygon) > 2 {