font/sfnt: implement rrcurveto.

Change-Id: I2e24293568b296dd916b2ef6a9c1113ffd5f9253
Reviewed-on: https://go-review.googlesource.com/34171
Reviewed-by: Dave Day <djd@golang.org>

font/sfnt/postscript.go

@@ -548,7 +548,7 @@ var psOperators = [...][2][]psOperator{
 		5:  {-1, "rlineto", t2CRlineto},
 		6:  {-1, "hlineto", t2CHlineto},
 		7:  {-1, "vlineto", t2CVlineto},
-		8:  {}, // rrcurveto.
+		8:  {-1, "rrcurveto", t2CRrcurveto},
 		9:  {}, // Reserved.
 		10: {}, // callsubr.
 		11: {}, // return.
@@ -834,6 +834,23 @@ func t2CVcurveto(p *psInterpreter, i int32) (j int32) {
 	return i
 }
 
+func t2CRrcurveto(p *psInterpreter) error {
+	if !p.type2Charstrings.seenWidth || p.stack.top < 6 || p.stack.top%6 != 0 {
+		return errInvalidCFFTable
+	}
+	for i := int32(0); i != p.stack.top; i += 6 {
+		t2CAppendCubeto(p,
+			p.stack.a[i+0],
+			p.stack.a[i+1],
+			p.stack.a[i+2],
+			p.stack.a[i+3],
+			p.stack.a[i+4],
+			p.stack.a[i+5],
+		)
+	}
+	return nil
+}
+
 func t2CEndchar(p *psInterpreter) error {
 	t2CReadWidth(p, 0)
 	if p.stack.top != 0 || len(p.instructions) != 0 {

font/sfnt/sfnt_test.go

@@ -125,6 +125,20 @@ func TestPostScript(t *testing.T) {
 		lineTo(300, 0),
 		lineTo(300, 800),
 		lineTo(100, 800),
+	}, {
+		// Q
+		// - contour #0
+		moveTo(657, 237),
+		lineTo(289, 387),
+		lineTo(519, 615),
+		// - contour #1
+		moveTo(792, 169),
+		cubeTo(867, 263, 926, 502, 791, 665),
+		cubeTo(645, 840, 380, 831, 228, 673),
+		cubeTo(71, 509, 110, 231, 242, 93),
+		cubeTo(369, -39, 641, 18, 722, 93),
+		lineTo(802, 3),
+		lineTo(864, 83),
 	}, {
 		// uni4E2D
 		// - contour #0

font/testdata/CFFTest.sfd

@@ -19,7 +19,7 @@ OS2Version: 0
 OS2_WeightWidthSlopeOnly: 0
 OS2_UseTypoMetrics: 1
 CreationTime: 1479626795
-ModificationTime: 1480661567
+ModificationTime: 1481282599
 PfmFamily: 17
 TTFWeight: 400
 TTFWidth: 5
@@ -48,11 +48,11 @@ NameList: Adobe Glyph List
 DisplaySize: -24
 AntiAlias: 1
 FitToEm: 1
-WinInfo: 19712 32 23
+WinInfo: 64 32 11
 BeginPrivate: 0
 EndPrivate
 TeXData: 1 0 0 346030 173015 115343 0 1048576 115343 783286 444596 497025 792723 393216 433062 380633 303038 157286 324010 404750 52429 2506097 1059062 262144
-BeginChars: 65536 3
+BeginChars: 65536 4
 
 StartChar: zero
 Encoding: 48 48 0
@@ -120,5 +120,29 @@ SplineSet
 EndSplineSet
 Validated: 1
 EndChar
+
+StartChar: Q
+Encoding: 81 81 3
+Width: 1000
+VWidth: 0
+Flags: W
+LayerCount: 2
+Fore
+SplineSet
+657 237 m 0
+ 519 615 l 0
+ 289 387 l 0
+ 657 237 l 0
+792 169 m 1
+ 864 83 l 25
+ 802 3 l 21
+ 722 93 l 1
+ 641 18 369 -39 242 93 c 0
+ 110 231 71 509 228 673 c 24
+ 380 831 645 840 791 665 c 0
+ 926 502 867 263 792 169 c 1
+EndSplineSet
+Validated: 33
+EndChar
 EndChars
 EndSplineFont