converted earcut.hpp library to Go and used it to triangulate fonts

canvas.go

@@ -27,10 +27,11 @@ type Canvas struct {
 	state      drawState
 	stateStack []drawState
 
-	images       map[interface{}]*Image
-	fonts        map[interface{}]*Font
-	fontCtxs     map[fontKey]*frCache
-	fontTriCache map[*Font]*fontTriCache
+	images        map[interface{}]*Image
+	fonts         map[interface{}]*Font
+	fontCtxs      map[fontKey]*frCache
+	fontPathCache map[*Font]*fontPathCache
+	fontTriCache  map[*Font]*fontTriCache
 
 	shadowBuf []backendbase.Vec
 }
@@ -139,12 +140,13 @@ var Performance = struct {
 // coordinates given here also use the bottom left as origin
 func New(backend backendbase.Backend) *Canvas {
 	cv := &Canvas{
-		b:            backend,
-		stateStack:   make([]drawState, 0, 20),
-		images:       make(map[interface{}]*Image),
-		fonts:        make(map[interface{}]*Font),
-		fontCtxs:     make(map[fontKey]*frCache),
-		fontTriCache: make(map[*Font]*fontTriCache),
+		b:             backend,
+		stateStack:    make([]drawState, 0, 20),
+		images:        make(map[interface{}]*Image),
+		fonts:         make(map[interface{}]*Font),
+		fontCtxs:      make(map[fontKey]*frCache),
+		fontPathCache: make(map[*Font]*fontPathCache),
+		fontTriCache:  make(map[*Font]*fontTriCache),
 	}
 	cv.state.lineWidth = 1
 	cv.state.lineAlpha = 1
@@ -482,6 +484,7 @@ func (cv *Canvas) reduceCache(keepSize, rec int) {
 	oldest := time.Now()
 	var oldestFontKey fontKey
 	var oldestFontKey2 *Font
+	var oldestFontKey3 *Font
 	var oldestImageKey interface{}
 	for src, img := range cv.images {
 		w, h := img.img.Size()
@@ -499,7 +502,7 @@ func (cv *Canvas) reduceCache(keepSize, rec int) {
 			oldestImageKey = nil
 		}
 	}
-	for fnt, cache := range cv.fontTriCache {
+	for fnt, cache := range cv.fontPathCache {
 		total += cache.size()
 		if cache.lastUsed.Before(oldest) {
 			oldest = cache.lastUsed
@@ -508,6 +511,16 @@ func (cv *Canvas) reduceCache(keepSize, rec int) {
 			oldestImageKey = nil
 		}
 	}
+	for fnt, cache := range cv.fontTriCache {
+		total += cache.size()
+		if cache.lastUsed.Before(oldest) {
+			oldest = cache.lastUsed
+			oldestFontKey3 = fnt
+			oldestFontKey2 = nil
+			oldestFontKey = fontKey{}
+			oldestImageKey = nil
+		}
+	}
 	if total <= keepSize {
 		return
 	}
@@ -516,7 +529,9 @@ func (cv *Canvas) reduceCache(keepSize, rec int) {
 		cv.images[oldestImageKey].Delete()
 		delete(cv.images, oldestImageKey)
 	} else if oldestFontKey2 != nil {
-		delete(cv.fontTriCache, oldestFontKey2)
+		delete(cv.fontPathCache, oldestFontKey2)
+	} else if oldestFontKey3 != nil {
+		delete(cv.fontTriCache, oldestFontKey3)
 	} else {
 		cv.fontCtxs[oldestFontKey].ctx = nil
 		delete(cv.fontCtxs, oldestFontKey)

earcut.go

@@ -0,0 +1,801 @@
+package canvas
+
+import (
+	"math"
+	"sort"
+
+	"github.com/tfriedel6/canvas/backend/backendbase"
+)
+
+// Go port of https://github.com/mapbox/earcut.hpp
+
+type node struct {
+	i    int
+	x, y float64
+
+	// previous and next vertice nodes in a polygon ring
+	prev *node
+	next *node
+
+	// z-order curve value
+	z int
+
+	// previous and next nodes in z-order
+	prevZ *node
+	nextZ *node
+
+	// indicates whether this is a steiner point
+	steiner bool
+}
+
+type earcut struct {
+	indices    []int
+	vertices   int
+	hashing    bool
+	minX, minY float64
+	maxX, maxY float64
+	invSize    float64
+	nodes      []node
+}
+
+func (ec *earcut) run(points [][]backendbase.Vec) {
+	if len(points) == 0 {
+		return
+	}
+
+	var x, y float64
+	threshold := 80
+	ln := 0
+
+	for i := 0; threshold >= 0 && i < len(points); i++ {
+		threshold -= len(points[i])
+		ln += len(points[i])
+	}
+
+	//estimate size of nodes and indices
+	ec.nodes = make([]node, 0, ln*3/2)
+	ec.indices = make([]int, 0, ln+len(points[0]))
+	ec.vertices = 0
+
+	outerNode := ec.linkedList(points[0], true)
+	if outerNode == nil || outerNode.prev == outerNode.next {
+		return
+	}
+
+	if len(points) > 1 {
+		outerNode = ec.eliminateHoles(points, outerNode)
+	}
+
+	// if the shape is not too simple, we'll use z-order curve hash later; calculate polygon bbox
+	ec.hashing = threshold < 0
+	if ec.hashing {
+		p := outerNode.next
+		ec.minX, ec.maxX = outerNode.x, outerNode.x
+		ec.minY, ec.maxY = outerNode.y, outerNode.y
+		for {
+			x = p.x
+			y = p.y
+			ec.minX = math.Min(ec.minX, x)
+			ec.minY = math.Min(ec.minY, y)
+			ec.maxX = math.Min(ec.maxX, x)
+			ec.maxY = math.Min(ec.maxY, y)
+			p = p.next
+			if p != outerNode {
+				break
+			}
+		}
+
+		// minX, minY and size are later used to transform coords into integers for z-order calculation
+		ec.invSize = math.Max(ec.maxX-ec.minX, ec.maxY-ec.minY)
+		if ec.invSize != 0 {
+			ec.invSize = 1 / ec.invSize
+		}
+	}
+
+	ec.earcutLinked(outerNode, 0)
+
+	ec.nodes = ec.nodes[:0]
+}
+
+// create a circular doubly linked list from polygon points in the specified winding order
+func (ec *earcut) linkedList(points []backendbase.Vec, clockwise bool) *node {
+	var sum float64
+	ln := len(points)
+	var i, j int
+	var last *node
+
+	// calculate original winding order of a polygon ring
+	if ln > 0 {
+		j = ln - 1
+	}
+	for i < ln {
+		p1 := points[i]
+		p2 := points[j]
+		p20 := p2[0]
+		p10 := p1[0]
+		p11 := p1[1]
+		p21 := p2[1]
+		sum += (p20 - p10) * (p11 + p21)
+		j = i
+		i++
+	}
+
+	// link points into circular doubly-linked list in the specified winding order
+	if clockwise == (sum > 0) {
+		for i := 0; i < ln; i++ {
+			last = ec.insertNode(ec.vertices+i, points[i], last)
+		}
+	} else {
+		for i = ln - 1; i >= 0; i-- {
+			last = ec.insertNode(ec.vertices+i, points[i], last)
+		}
+	}
+
+	if last != nil && ec.equals(last, last.next) {
+		ec.removeNode(last)
+		last = last.next
+	}
+
+	ec.vertices += ln
+
+	return last
+}
+
+// eliminate colinear or duplicate points
+func (ec *earcut) filterPoints(start, end *node) *node {
+	if end == nil {
+		end = start
+	}
+
+	p := start
+	var again bool
+	for {
+		again = false
+
+		if !p.steiner && (ec.equals(p, p.next) || ec.area(p.prev, p, p.next) == 0) {
+			ec.removeNode(p)
+			p, end = p.prev, p.prev
+
+			if p == p.next {
+				break
+			}
+			again = true
+
+		} else {
+			p = p.next
+		}
+		if !again && p == end {
+			break
+		}
+	}
+
+	return end
+}
+
+// main ear slicing loop which triangulates a polygon (given as a linked list)
+func (ec *earcut) earcutLinked(ear *node, pass int) {
+	if ear == nil {
+		return
+	}
+
+	// interlink polygon nodes in z-order
+	if pass == 0 && ec.hashing {
+		ec.indexCurve(ear)
+	}
+
+	stop := ear
+	var prev, next *node
+
+	iterations := 0
+
+	// iterate through ears, slicing them one by one
+	for ear.prev != ear.next {
+		iterations++
+		prev = ear.prev
+		next = ear.next
+
+		var e bool
+		if ec.hashing {
+			e = ec.isEarHashed(ear)
+		} else {
+			e = ec.isEar(ear)
+		}
+		if e {
+			// cut off the triangle
+			ec.indices = append(ec.indices, prev.i, ear.i, next.i)
+
+			ec.removeNode(ear)
+
+			// skipping the next vertice leads to less sliver triangles
+			ear = next.next
+			stop = next.next
+
+			continue
+		}
+
+		ear = next
+
+		// if we looped through the whole remaining polygon and can't find any more ears
+		if ear == stop {
+			// try filtering points and slicing again
+			if pass == 0 {
+				ec.earcutLinked(ec.filterPoints(ear, nil), 1)
+			} else if pass == 1 {
+				// if this didn't work, try curing all small self-intersections locally
+				ear = ec.cureLocalIntersections(ec.filterPoints(ear, nil))
+				ec.earcutLinked(ear, 2)
+			} else if pass == 2 {
+				// as a last resort, try splitting the remaining polygon into two
+				ec.splitEarcut(ear)
+			}
+
+			break
+		}
+	}
+}
+
+// check whether a polygon node forms a valid ear with adjacent nodes
+func (ec *earcut) isEar(ear *node) bool {
+	a := ear.prev
+	b := ear
+	c := ear.next
+
+	if ec.area(a, b, c) >= 0 {
+		return false // reflex, can't be an ear
+	}
+
+	// now make sure we don't have other points inside the potential ear
+	p := ear.next.next
+
+	for p != ear.prev {
+		if ec.pointInTriangle(a.x, a.y, b.x, b.y, c.x, c.y, p.x, p.y) &&
+			ec.area(p.prev, p, p.next) >= 0 {
+			return false
+		}
+		p = p.next
+	}
+
+	return true
+}
+
+func (ec *earcut) isEarHashed(ear *node) bool {
+	a := ear.prev
+	b := ear
+	c := ear.next
+
+	if ec.area(a, b, c) >= 0 {
+		return false // reflex, can't be an ear
+	}
+
+	// triangle bbox; min & max are calculated like this for speed
+
+	minTX := math.Min(a.x, math.Min(b.x, c.x))
+	minTY := math.Min(a.y, math.Min(b.y, c.y))
+	maxTX := math.Max(a.x, math.Max(b.x, c.x))
+	maxTY := math.Max(a.y, math.Max(b.y, c.y))
+
+	// z-order range for the current triangle bbox;
+	minZ := ec.zOrder(minTX, minTY)
+	maxZ := ec.zOrder(maxTX, maxTY)
+
+	// first look for points inside the triangle in increasing z-order
+	p := ear.nextZ
+
+	for p != nil && p.z <= maxZ {
+		if p != ear.prev && p != ear.next &&
+			ec.pointInTriangle(a.x, a.y, b.x, b.y, c.x, c.y, p.x, p.y) &&
+			ec.area(p.prev, p, p.next) >= 0 {
+			return false
+		}
+		p = p.nextZ
+	}
+
+	// then look for points in decreasing z-order
+	p = ear.prevZ
+
+	for p != nil && p.z >= minZ {
+		if p != ear.prev && p != ear.next &&
+			ec.pointInTriangle(a.x, a.y, b.x, b.y, c.x, c.y, p.x, p.y) &&
+			ec.area(p.prev, p, p.next) >= 0 {
+			return false
+		}
+		p = p.prevZ
+	}
+
+	return true
+}
+
+// go through all polygon nodes and cure small local self-intersections
+func (ec *earcut) cureLocalIntersections(start *node) *node {
+	p := start
+	for {
+		a := p.prev
+		b := p.next.next
+
+		// a self-intersection where edge (v[i-1],v[i]) intersects (v[i+1],v[i+2])
+		if !ec.equals(a, b) && ec.intersects(a, p, p.next, b) && ec.locallyInside(a, b) && ec.locallyInside(b, a) {
+			ec.indices = append(ec.indices, a.i, p.i, b.i)
+
+			// remove two nodes involved
+			ec.removeNode(p)
+			ec.removeNode(p.next)
+
+			p, start = b, b
+		}
+		p = p.next
+		if p == start {
+			break
+		}
+	}
+
+	return ec.filterPoints(p, nil)
+}
+
+// try splitting polygon into two and triangulate them independently
+func (ec *earcut) splitEarcut(start *node) {
+	// look for a valid diagonal that divides the polygon into two
+	a := start
+	for {
+		b := a.next.next
+		for b != a.prev {
+			if a.i != b.i && ec.isValidDiagonal(a, b) {
+				// split the polygon in two by the diagonal
+				c := ec.splitPolygon(a, b)
+
+				// filter colinear points around the cuts
+				a = ec.filterPoints(a, a.next)
+				c = ec.filterPoints(c, c.next)
+
+				// run earcut on each half
+				ec.earcutLinked(a, 0)
+				ec.earcutLinked(c, 0)
+				return
+			}
+			b = b.next
+		}
+		a = a.next
+		if a == start {
+			break
+		}
+	}
+}
+
+// link every hole into the outer loop, producing a single-ring polygon without holes
+func (ec *earcut) eliminateHoles(points [][]backendbase.Vec, outerNode *node) *node {
+	ln := len(points)
+
+	queue := make([]*node, 0, ln)
+	for i := 1; i < ln; i++ {
+		list := ec.linkedList(points[i], false)
+		if list != nil {
+			if list == list.next {
+				list.steiner = true
+			}
+			queue = append(queue, ec.getLeftmost(list))
+		}
+	}
+	sort.Slice(queue, func(a, b int) bool {
+		return queue[a].x < queue[b].x
+	})
+
+	// process holes from left to right
+	for i := 0; i < len(queue); i++ {
+		ec.eliminateHole(queue[i], outerNode)
+		outerNode = ec.filterPoints(outerNode, outerNode.next)
+	}
+
+	return outerNode
+}
+
+// find a bridge between vertices that connects hole with an outer ring and and link it
+func (ec *earcut) eliminateHole(hole, outerNode *node) {
+	outerNode = ec.findHoleBridge(hole, outerNode)
+	if outerNode != nil {
+		b := ec.splitPolygon(outerNode, hole)
+
+		// filter out colinear points around cuts
+		ec.filterPoints(outerNode, outerNode.next)
+		ec.filterPoints(b, b.next)
+	}
+}
+
+// David Eberly's algorithm for finding a bridge between hole and outer polygon
+func (ec *earcut) findHoleBridge(hole, outerNode *node) *node {
+	p := outerNode
+	hx := hole.x
+	hy := hole.y
+	qx := math.Inf(-1)
+	var m *node
+
+	// find a segment intersected by a ray from the hole's leftmost Vertex to the left;
+	// segment's endpoint with lesser x will be potential connection Vertex
+	for {
+		if hy <= p.y && hy >= p.next.y && p.next.y != p.y {
+			x := p.x + (hy-p.y)*(p.next.x-p.x)/(p.next.y-p.y)
+			if x <= hx && x > qx {
+				qx = x
+				if x == hx {
+					if hy == p.y {
+						return p
+					}
+					if hy == p.next.y {
+						return p.next
+					}
+				}
+				if p.x < p.next.x {
+					m = p
+				} else {
+					m = p.next
+				}
+			}
+		}
+		p = p.next
+		if p == outerNode {
+			break
+		}
+	}
+
+	if m == nil {
+		return nil
+	}
+
+	if hx == qx {
+		return m // hole touches outer segment; pick leftmost endpoint
+	}
+
+	// look for points inside the triangle of hole Vertex, segment intersection and endpoint;
+	// if there are no points found, we have a valid connection;
+	// otherwise choose the Vertex of the minimum angle with the ray as connection Vertex
+
+	stop := m
+	tanMin := math.Inf(1)
+	tanCur := 0.0
+
+	p = m
+	mx := m.x
+	my := m.y
+
+	for {
+		var pt1, pt2 float64
+		if hy < my {
+			pt1 = hx
+			pt2 = qx
+		} else {
+			pt1 = qx
+			pt2 = hx
+		}
+		if hx >= p.x && p.x >= mx && hx != p.x &&
+			ec.pointInTriangle(pt1, hy, mx, my, pt2, hy, p.x, p.y) {
+
+			tanCur = math.Abs(hy-p.y) / (hx - p.x) // tangential
+
+			if ec.locallyInside(p, hole) &&
+				(tanCur < tanMin || (tanCur == tanMin && (p.x > m.x || ec.sectorContainsSector(m, p)))) {
+				m = p
+				tanMin = tanCur
+			}
+		}
+
+		p = p.next
+		if p == stop {
+			break
+		}
+	}
+
+	return m
+}
+
+// whether sector in vertex m contains sector in vertex p in the same coordinates
+func (ec *earcut) sectorContainsSector(m, p *node) bool {
+	return ec.area(m.prev, m, p.prev) < 0 && ec.area(p.next, m, m.next) < 0
+}
+
+// interlink polygon nodes in z-order
+func (ec *earcut) indexCurve(start *node) {
+	if start == nil {
+		panic("start must not be nil")
+	}
+	p := start
+
+	for {
+		if p.z <= 0 {
+			p.z = ec.zOrder(p.x, p.y)
+		}
+		p.prevZ = p.prev
+		p.nextZ = p.next
+		p = p.next
+		if p == start {
+			break
+		}
+	}
+
+	p.prevZ.nextZ = nil
+	p.prevZ = nil
+
+	ec.sortLinked(p)
+}
+
+// Simon Tatham's linked list merge sort algorithm
+// http://www.chiark.greenend.org.uk/~sgtatham/algorithms/listsort.html
+func (ec *earcut) sortLinked(list *node) *node {
+	if list == nil {
+		panic("list must not be nil")
+	}
+	var p, q, e, tail *node
+	var i, numMerges, pSize, qSize int
+	inSize := 1
+
+	for {
+		p = list
+		list = nil
+		tail = nil
+		numMerges = 0
+
+		for p != nil {
+			numMerges++
+			q = p
+			pSize = 0
+			for i = 0; i < inSize; i++ {
+				pSize++
+				q = q.nextZ
+				if q == nil {
+					break
+				}
+			}
+
+			qSize = inSize
+
+			for pSize > 0 || (qSize > 0 && q != nil) {
+
+				if pSize == 0 {
+					e = q
+					q = q.nextZ
+					qSize--
+				} else if qSize == 0 || q == nil {
+					e = p
+					p = p.nextZ
+					pSize--
+				} else if p.z <= q.z {
+					e = p
+					p = p.nextZ
+					pSize--
+				} else {
+					e = q
+					q = q.nextZ
+					qSize--
+				}
+
+				if tail != nil {
+					tail.nextZ = e
+				} else {
+					list = e
+				}
+
+				e.prevZ = tail
+				tail = e
+			}
+
+			p = q
+		}
+
+		tail.nextZ = nil
+
+		if numMerges <= 1 {
+			return list
+		}
+
+		inSize *= 2
+	}
+}
+
+// z-order of a Vertex given coords and size of the data bounding box
+func (ec *earcut) zOrder(x, y float64) int {
+	// coords are transformed into non-negative 15-bit integer range
+	x2 := int(32767.0 * (x - ec.minX) * ec.invSize)
+	y2 := int(32767.0 * (y - ec.minY) * ec.invSize)
+
+	x2 = (x2 | (x2 << 8)) & 0x00FF00FF
+	x2 = (x2 | (x2 << 4)) & 0x0F0F0F0F
+	x2 = (x2 | (x2 << 2)) & 0x33333333
+	x2 = (x2 | (x2 << 1)) & 0x55555555
+
+	y2 = (y2 | (y2 << 8)) & 0x00FF00FF
+	y2 = (y2 | (y2 << 4)) & 0x0F0F0F0F
+	y2 = (y2 | (y2 << 2)) & 0x33333333
+	y2 = (y2 | (y2 << 1)) & 0x55555555
+
+	return x2 | (y2 << 1)
+}
+
+// find the leftmost node of a polygon ring
+func (ec *earcut) getLeftmost(start *node) *node {
+	p := start
+	leftmost := start
+	for {
+		if p.x < leftmost.x || (p.x == leftmost.x && p.y < leftmost.y) {
+			leftmost = p
+		}
+		p = p.next
+		if p == start {
+			break
+		}
+	}
+
+	return leftmost
+}
+
+// check if a point lies within a convex triangle
+func (ec *earcut) pointInTriangle(ax, ay, bx, by, cx, cy, px, py float64) bool {
+	return (cx-px)*(ay-py)-(ax-px)*(cy-py) >= 0 &&
+		(ax-px)*(by-py)-(bx-px)*(ay-py) >= 0 &&
+		(bx-px)*(cy-py)-(cx-px)*(by-py) >= 0
+}
+
+// check if a diagonal between two polygon nodes is valid (lies in polygon interior)
+func (ec *earcut) isValidDiagonal(a, b *node) bool {
+	return a.next.i != b.i && a.prev.i != b.i && !ec.intersectsPolygon(a, b) && // dones't intersect other edges
+		((ec.locallyInside(a, b) && ec.locallyInside(b, a) && ec.middleInside(a, b) && // locally visible
+			(ec.area(a.prev, a, b.prev) != 0.0 || ec.area(a, b.prev, b) != 0.0)) || // does not create opposite-facing sectors
+			(ec.equals(a, b) && ec.area(a.prev, a, a.next) > 0 && ec.area(b.prev, b, b.next) > 0)) // special zero-length case
+}
+
+// signed area of a triangle
+func (ec *earcut) area(p, q, r *node) float64 {
+	return (q.y-p.y)*(r.x-q.x) - (q.x-p.x)*(r.y-q.y)
+}
+
+// check if two points are equal
+func (ec *earcut) equals(p1, p2 *node) bool {
+	return p1.x == p2.x && p1.y == p2.y
+}
+
+// check if two segments intersect
+func (ec *earcut) intersects(p1, q1, p2, q2 *node) bool {
+	o1 := ec.sign(ec.area(p1, q1, p2))
+	o2 := ec.sign(ec.area(p1, q1, q2))
+	o3 := ec.sign(ec.area(p2, q2, p1))
+	o4 := ec.sign(ec.area(p2, q2, q1))
+
+	if o1 != o2 && o3 != o4 {
+		return true // general case
+	}
+
+	if o1 == 0 && ec.onSegment(p1, p2, q1) {
+		// p1, q1 and p2 are collinear and p2 lies on p1q1
+		return true
+	}
+	if o2 == 0 && ec.onSegment(p1, q2, q1) {
+		// p1, q1 and q2 are collinear and q2 lies on p1q1
+		return true
+	}
+	if o3 == 0 && ec.onSegment(p2, p1, q2) {
+		// p2, q2 and p1 are collinear and p1 lies on p2q2
+		return true
+	}
+	if o4 == 0 && ec.onSegment(p2, q1, q2) {
+		// p2, q2 and q1 are collinear and q1 lies on p2q2
+		return true
+	}
+
+	return false
+}
+
+// for collinear points p, q, r, check if point q lies on segment pr
+func (ec *earcut) onSegment(p, q, r *node) bool {
+	return q.x <= math.Max(p.x, r.x) &&
+		q.x >= math.Min(p.x, r.x) &&
+		q.y <= math.Max(p.y, r.y) &&
+		q.y >= math.Min(p.y, r.y)
+}
+
+func (ec *earcut) sign(val float64) int {
+	if val < 0 {
+		return -1
+	} else if val > 0 {
+		return 1
+	}
+	return 0
+}
+
+// check if a polygon diagonal intersects any polygon segments
+func (ec *earcut) intersectsPolygon(a, b *node) bool {
+	p := a
+	for {
+		if p.i != a.i && p.next.i != a.i && p.i != b.i && p.next.i != b.i &&
+			ec.intersects(p, p.next, a, b) {
+			return true
+		}
+		p = p.next
+		if p == a {
+			break
+		}
+	}
+
+	return false
+}
+
+// check if a polygon diagonal is locally inside the polygon
+func (ec *earcut) locallyInside(a, b *node) bool {
+	if ec.area(a.prev, a, a.next) < 0 {
+		return ec.area(a, b, a.next) >= 0 && ec.area(a, a.prev, b) >= 0
+	}
+	return ec.area(a, b, a.prev) < 0 || ec.area(a, a.next, b) < 0
+}
+
+// check if the middle Vertex of a polygon diagonal is inside the polygon
+func (ec *earcut) middleInside(a, b *node) bool {
+	p := a
+	inside := false
+	px := (a.x + b.x) / 2
+	py := (a.y + b.y) / 2
+	for {
+		if ((p.y > py) != (p.next.y > py)) && p.next.y != p.y &&
+			(px < (p.next.x-p.x)*(py-p.y)/(p.next.y-p.y)+p.x) {
+			inside = !inside
+		}
+		p = p.next
+		if p == a {
+			break
+		}
+	}
+
+	return inside
+}
+
+// link two polygon vertices with a bridge; if the vertices belong to the same ring, it splits
+// polygon into two; if one belongs to the outer ring and another to a hole, it merges it into a
+// single ring
+func (ec *earcut) splitPolygon(a, b *node) *node {
+	ec.nodes = append(ec.nodes, node{i: a.i, x: a.x, y: a.y})
+	a2 := &ec.nodes[len(ec.nodes)-1]
+	ec.nodes = append(ec.nodes, node{i: b.i, x: b.x, y: b.y})
+	b2 := &ec.nodes[len(ec.nodes)-1]
+	an := a.next
+	bp := b.prev
+
+	a.next = b
+	b.prev = a
+
+	a2.next = an
+	an.prev = a2
+
+	b2.next = a2
+	a2.prev = b2
+
+	bp.next = b2
+	b2.prev = bp
+
+	return b2
+}
+
+// create a node and util::optionally link it with previous one (in a circular doubly linked list)
+func (ec *earcut) insertNode(i int, pt backendbase.Vec, last *node) *node {
+	ec.nodes = append(ec.nodes, node{i: i, x: pt[0], y: pt[1]})
+	p := &ec.nodes[len(ec.nodes)-1]
+
+	if last == nil {
+		p.prev = p
+		p.next = p
+	} else {
+		if last == nil {
+			panic("last must not be nil")
+		}
+		p.next = last.next
+		p.prev = last
+		last.next.prev = p
+		last.next = p
+	}
+	return p
+}
+
+func (ec *earcut) removeNode(p *node) {
+	p.next.prev = p.prev
+	p.prev.next = p.next
+
+	if p.prevZ != nil {
+		p.prevZ.nextZ = p.nextZ
+	}
+	if p.nextZ != nil {
+		p.nextZ.prevZ = p.prevZ
+	}
+}

text.go

@@ -34,16 +34,29 @@ type frCache struct {
 	lastUsed time.Time
 }
 
-type fontTriCache struct {
+type fontPathCache struct {
 	cache    map[truetype.Index]*Path2D
 	lastUsed time.Time
 }
 
+func (fpc *fontPathCache) size() int {
+	size := 0
+	pps := int(unsafe.Sizeof(pathPoint{}))
+	for _, p := range fpc.cache {
+		size += len(p.p) * pps
+	}
+	return size
+}
+
+type fontTriCache struct {
+	cache    map[truetype.Index][]backendbase.Vec
+	lastUsed time.Time
+}
+
 func (ftc *fontTriCache) size() int {
 	size := 0
-	pps := int(unsafe.Sizeof(pathPoint{}))
 	for _, p := range ftc.cache {
-		size += len(p.p) * pps
+		size += len(p) * 16
 	}
 	return size
 }
@@ -140,11 +153,10 @@ func (cv *Canvas) FillText(str string, x, y float64) {
 	scale := (scaleX + scaleY) * 0.5
 	fontSize := fixed.Int26_6(math.Round(float64(cv.state.fontSize) * scale))
 
-	// if fontSize > fixed.I(30) {
-	// if time.Now().Second()%2 == 0 {
-	// 	cv.fillText2(str, x, y)
-	// 	return
-	// }
+	if fontSize > fixed.I(25) {
+		cv.fillText2(str, x, y)
+		return
+	}
 
 	frc := cv.getFRContext(cv.state.font, fontSize)
 	fnt := cv.state.font.font
@@ -258,9 +270,11 @@ func (cv *Canvas) fillText2(str string, x, y float64) {
 			continue
 		}
 
-		path := cv.runePath(rn)
+		tris := cv.runeTris(rn)
 		tf := scaleMat.Mul(backendbase.MatTranslate(backendbase.Vec{x, y})).Mul(cv.state.transform)
-		cv.fillPath(path, tf)
+		cv.drawShadow(tris, nil, false)
+		stl := cv.backendFillStyle(&cv.state.fill, 1)
+		cv.b.Fill(&stl, tris, tf, false)
 
 		x += float64(advance) / 64
 	}
@@ -483,7 +497,7 @@ func (cv *Canvas) runePath(rn rune) *Path2D {
 		idx = cv.state.font.font.Index(' ')
 	}
 
-	if cache, ok := cv.fontTriCache[cv.state.font]; ok {
+	if cache, ok := cv.fontPathCache[cv.state.font]; ok {
 		if path, ok := cache.cache[idx]; ok {
 			cache.lastUsed = time.Now()
 			return path
@@ -553,10 +567,10 @@ func (cv *Canvas) runePath(rn rune) *Path2D {
 		from = to
 	}
 
-	cache, ok := cv.fontTriCache[cv.state.font]
+	cache, ok := cv.fontPathCache[cv.state.font]
 	if !ok {
-		cache = &fontTriCache{cache: make(map[truetype.Index]*Path2D, 1024)}
-		cv.fontTriCache[cv.state.font] = cache
+		cache = &fontPathCache{cache: make(map[truetype.Index]*Path2D, 1024)}
+		cv.fontPathCache[cv.state.font] = cache
 	}
 	cache.lastUsed = time.Now()
 	cache.cache[idx] = path
@@ -564,6 +578,116 @@ func (cv *Canvas) runePath(rn rune) *Path2D {
 	return path
 }
 
+func (cv *Canvas) runeTris(rn rune) []backendbase.Vec {
+	idx := cv.state.font.font.Index(rn)
+	if idx == 0 {
+		idx = cv.state.font.font.Index(' ')
+	}
+
+	if cache, ok := cv.fontTriCache[cv.state.font]; ok {
+		if tris, ok := cache.cache[idx]; ok {
+			cache.lastUsed = time.Now()
+			return tris
+		}
+	}
+
+	const scale = 1.0 / 64.0
+
+	var gb truetype.GlyphBuf
+	gb.Load(cv.state.font.font, baseFontSize, idx, font.HintingFull)
+
+	polyWithHoles := make([][]backendbase.Vec, 0, len(gb.Ends))
+
+	from := 0
+	for _, to := range gb.Ends {
+		ps := gb.Points[from:to]
+
+		start := ps[0]
+		others := []truetype.Point(nil)
+		if ps[0].Flags&0x01 != 0 {
+			others = ps[1:]
+		} else {
+			last := ps[len(ps)-1]
+			if ps[len(ps)-1].Flags&0x01 != 0 {
+				start = last
+				others = ps[:len(ps)-1]
+			} else {
+				start = truetype.Point{
+					X: (start.X + last.X) / 2,
+					Y: (start.Y + last.Y) / 2,
+				}
+				others = ps
+			}
+		}
+
+		p0, on0 := start, true
+		path := &Path2D{cv: cv, p: make([]pathPoint, 0, 50), standalone: true, noSelfIntersection: true}
+		path.MoveTo(float64(p0.X)*scale, -float64(p0.Y)*scale)
+		for _, p := range others {
+			on := p.Flags&0x01 != 0
+			if on {
+				if on0 {
+					path.LineTo(float64(p.X)*scale, -float64(p.Y)*scale)
+				} else {
+					path.QuadraticCurveTo(float64(p0.X)*scale, -float64(p0.Y)*scale, float64(p.X)*scale, -float64(p.Y)*scale)
+				}
+			} else {
+				if on0 {
+					// No-op.
+				} else {
+					mid := fixed.Point26_6{
+						X: (p0.X + p.X) / 2,
+						Y: (p0.Y + p.Y) / 2,
+					}
+					path.QuadraticCurveTo(float64(p0.X)*scale, -float64(p0.Y)*scale, float64(mid.X)*scale, -float64(mid.Y)*scale)
+				}
+			}
+			p0, on0 = p, on
+		}
+
+		if on0 {
+			path.LineTo(float64(start.X)*scale, -float64(start.Y)*scale)
+		} else {
+			path.QuadraticCurveTo(float64(p0.X)*scale, -float64(p0.Y)*scale, float64(start.X)*scale, -float64(start.Y)*scale)
+		}
+		path.ClosePath()
+
+		poly := make([]backendbase.Vec, len(path.p))
+		for i, pt := range path.p {
+			poly[i] = pt.pos
+		}
+
+		polyWithHoles = append(polyWithHoles, poly)
+
+		from = to
+	}
+
+	var ec earcut
+	ec.run(polyWithHoles)
+
+	tris := make([]backendbase.Vec, len(ec.indices))
+	for i, idx := range ec.indices {
+		pidx := 0
+		poly := polyWithHoles[pidx]
+		for idx >= len(poly) {
+			idx -= len(poly)
+			pidx++
+			poly = polyWithHoles[pidx]
+		}
+		tris[i] = poly[idx]
+	}
+
+	cache, ok := cv.fontTriCache[cv.state.font]
+	if !ok {
+		cache = &fontTriCache{cache: make(map[truetype.Index][]backendbase.Vec, 1024)}
+		cv.fontTriCache[cv.state.font] = cache
+	}
+	cache.lastUsed = time.Now()
+	cache.cache[idx] = tris
+
+	return tris
+}
+
 // TextMetrics is the result of a MeasureText call
 type TextMetrics struct {
 	Width                    float64