From 4c33bd09f5bece0cbc1e5f8c763e161e03202b02 Mon Sep 17 00:00:00 2001
From: Nigel Tao <nigeltao@golang.org>
Date: Wed, 4 Dec 2013 10:04:19 +1100
Subject: [PATCH] freetype/truetype: implement SCFS, FLIPPT, FLIPRGON,
 FLIPRGOFF opcodes.

R=bsiegert
CC=golang-dev, remyoudompheng
https://codereview.appspot.com/36300043
---
 freetype/truetype/hint.go          | 48 ++++++++++++++++++++++++++++++
 freetype/truetype/opcodes.go       | 12 ++++----
 freetype/truetype/truetype_test.go |  4 +--
 3 files changed, 56 insertions(+), 8 deletions(-)

diff --git a/freetype/truetype/hint.go b/freetype/truetype/hint.go
index 53ef444..193c157 100644
--- a/freetype/truetype/hint.go
+++ b/freetype/truetype/hint.go
@@ -754,6 +754,25 @@ func (h *Hinter) run(program []byte, pCurrent, pUnhinted, pInFontUnits []Point,
 				h.stack[top-1] = int32(dotProduct(f26dot6(p.X), f26dot6(p.Y), h.gs.dv))
 			}
 
+		case opSCFS:
+			top -= 2
+			i := h.stack[top]
+			p := h.point(2, current, i)
+			if p == nil {
+				return errors.New("truetype: hinting: point out of range")
+			}
+			c := dotProduct(f26dot6(p.X), f26dot6(p.Y), h.gs.pv)
+			h.move(p, f26dot6(h.stack[top+1])-c, true)
+			if h.gs.zp[2] != 0 {
+				break
+			}
+			q := h.point(2, unhinted, i)
+			if q == nil {
+				return errors.New("truetype: hinting: point out of range")
+			}
+			q.X = p.X
+			q.Y = p.Y
+
 		case opMD0, opMD1:
 			top--
 			i, j := h.stack[top-1], h.stack[top]
@@ -960,6 +979,35 @@ func (h *Hinter) run(program []byte, pCurrent, pUnhinted, pInFontUnits []Point,
 			// These ops are "anachronistic" and no longer used.
 			top--
 
+		case opFLIPPT:
+			if top < int(h.gs.loop) {
+				return errors.New("truetype: hinting: stack underflow")
+			}
+			points := h.points[glyphZone][current]
+			for ; h.gs.loop != 0; h.gs.loop-- {
+				top--
+				i := h.stack[top]
+				if i < 0 || len(points) <= int(i) {
+					return errors.New("truetype: hinting: point out of range")
+				}
+				points[i].Flags ^= flagOnCurve
+			}
+			h.gs.loop = 1
+
+		case opFLIPRGON, opFLIPRGOFF:
+			top -= 2
+			i, j, points := h.stack[top], h.stack[top+1], h.points[glyphZone][current]
+			if i < 0 || len(points) <= int(i) || j < 0 || len(points) <= int(j) {
+				return errors.New("truetype: hinting: point out of range")
+			}
+			for ; i <= j; i++ {
+				if opcode == opFLIPRGON {
+					points[i].Flags |= flagOnCurve
+				} else {
+					points[i].Flags &^= flagOnCurve
+				}
+			}
+
 		case opSCANCTRL:
 			// We do not support dropout control, as we always rasterize grayscale glyphs.
 			top--
diff --git a/freetype/truetype/opcodes.go b/freetype/truetype/opcodes.go
index cfe3b32..d5e9bdc 100644
--- a/freetype/truetype/opcodes.go
+++ b/freetype/truetype/opcodes.go
@@ -82,7 +82,7 @@ const (
 	opRCVT      = 0x45 // Read Control Value Table entry
 	opGC0       = 0x46 // Get Coordinate projected onto the projection vector
 	opGC1       = 0x47 // .
-	opSCFS      = 0x48
+	opSCFS      = 0x48 // Sets Coordinate From the Stack using projection vector and freedom vector
 	opMD0       = 0x49 // Measure Distance
 	opMD1       = 0x4a // .
 	opMPPEM     = 0x4b // Measure Pixels Per EM
@@ -138,9 +138,9 @@ const (
 	opRDTG      = 0x7d // Round Down To Grid
 	opSANGW     = 0x7e // Set ANGle Weight
 	opAA        = 0x7f // Adjust Angle
-	opFLIPPT    = 0x80
-	opFLIPRGON  = 0x81
-	opFLIPRGOFF = 0x82
+	opFLIPPT    = 0x80 // FLIP PoinT
+	opFLIPRGON  = 0x81 // FLIP RanGe ON
+	opFLIPRGOFF = 0x82 // FLIP RanGe OFF
 	op_0x83     = 0x83
 	op_0x84     = 0x84
 	opSCANCTRL  = 0x85 // SCAN conversion ConTRoL
@@ -275,11 +275,11 @@ var popCount = [256]uint8{
 	1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 1, 0, 1, 1, 1, 1, // 0x10 - 0x1f
 	1, 1, 0, 2, 0, 1, 1, q, q, q, 2, 1, 1, 0, 1, 1, // 0x20 - 0x2f
 	0, 0, 0, 0, 1, 1, 1, 1, 1, 0, 2, 2, 0, 0, 2, 2, // 0x30 - 0x3f
-	0, 0, 2, 1, 2, 1, 1, 1, q, 2, 2, 0, 0, 0, 0, 0, // 0x40 - 0x4f
+	0, 0, 2, 1, 2, 1, 1, 1, 2, 2, 2, 0, 0, 0, 0, 0, // 0x40 - 0x4f
 	2, 2, 2, 2, 2, 2, 1, 1, 1, 0, 2, 2, 1, 1, 1, 1, // 0x50 - 0x5f
 	2, 2, 2, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, // 0x60 - 0x6f
 	2, 1, 1, 1, 1, 1, 1, 1, 2, 2, 0, q, 0, 0, 1, 1, // 0x70 - 0x7f
-	q, q, q, q, q, 1, 2, 2, 1, 1, 3, 2, 2, 1, q, q, // 0x80 - 0x8f
+	0, 2, 2, q, q, 1, 2, 2, 1, 1, 3, 2, 2, 1, q, q, // 0x80 - 0x8f
 	q, q, q, q, q, q, q, q, q, q, q, q, q, q, q, q, // 0x90 - 0x9f
 	q, q, q, q, q, q, q, q, q, q, q, q, q, q, q, q, // 0xa0 - 0xaf
 	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 0xb0 - 0xbf
diff --git a/freetype/truetype/truetype_test.go b/freetype/truetype/truetype_test.go
index 4f07eba..9e425ae 100644
--- a/freetype/truetype/truetype_test.go
+++ b/freetype/truetype/truetype_test.go
@@ -255,8 +255,8 @@ var scalingTestCases = []struct {
 	{"luxisr", 12, -1},
 	{"x-arial-bold", 11, -1},
 	{"x-deja-vu-sans-oblique", 17, -1},
-	{"x-droid-sans-japanese", 9, 0},
-	{"x-times-new-roman", 13, 0},
+	{"x-droid-sans-japanese", 9, -1},
+	{"x-times-new-roman", 13, 8},
 }
 
 // TODO: also test bounding boxes, not just points.