code review 6194050: freetype: support TrueType Collection files (.TTC files... (issue 6194050)

[nige...@golang.org]

Reviewers: bradfitz,

Message:
Hello brad...@golang.org (cc: golan...@googlegroups.com),

I'd like you to review this change to
https://code.google.com/p/freetype-go


Description:
freetype: support TrueType Collection files (.TTC files, as opposed to
.TTF files)

Please review this at http://codereview.appspot.com/6194050/

Affected files:
M freetype/truetype/truetype.go


Index: freetype/truetype/truetype.go
===================================================================
--- a/freetype/truetype/truetype.go
+++ b/freetype/truetype/truetype.go
@@ -3,9 +3,9 @@
// FreeType License or the GNU General Public License version 2 (or
// any later version), both of which can be found in the LICENSE file.

-// The truetype package provides a parser for the TTF file format. That
format
-// is documented at http://developer.apple.com/fonts/TTRefMan/ and
-// http://www.microsoft.com/typography/otspec/
+// The truetype package provides a parser for the TTF and TTC file formats.
+// Those formats are documented at
http://developer.apple.com/fonts/TTRefMan/
+// and http://www.microsoft.com/typography/otspec/
//
// All numbers (e.g. bounds, point co-ordinates, font metrics) are
measured in
// FUnits. To convert from FUnits to pixels, scale by
@@ -350,15 +350,52 @@
return 0
}

-// Parse returns a new Font for the given TTF data.
+// Parse returns a new Font for the given TTF or TTC data.
+//
+// For TrueType Collections, the first font in the collection is parsed.
func Parse(ttf []byte) (font *Font, err error) {
- if len(ttf) < 12 {
+ return parse(ttf, 0)
+}
+
+func parse(ttf []byte, offset int) (font *Font, err error) {
+ if len(ttf)-offset < 12 {
err = FormatError("TTF data is too short")
return
}
- d := data(ttf[0:])
- if d.u32() != 0x00010000 {
- err = FormatError("bad version")
+ d := data(ttf[offset:])
+ switch d.u32() {
+ case 0x00010000:
+ // No-op.
+ case 0x74746366: // "ttcf" as a big-endian uint32.
+ if offset != 0 {
+ err = FormatError("recursive TTC")
+ return
+ }
+ if d.u32() != 0x00010000 {
+ // TODO: support TTC version 2.0, once I have such a .ttc file to test
with.
+ err = FormatError("bad TTC version")
+ return
+ }
+ numFonts := int(d.u32())
+ if numFonts <= 0 {
+ err = FormatError("bad number of TTC fonts")
+ return
+ }
+ if len(d)/4 < numFonts {
+ err = FormatError("TTC offset table is too short")
+ return
+ }
+ // TODO: provide an API to select which font in a TrueType collection to
return,
+ // not just the first one. This may require an API to parse a TTC's name
tables,
+ // so users of this package can select the font in a TTC by name.
+ offset := int(d.u32())
+ if offset < 0 || offset > len(ttf) {
+ err = FormatError("TTC offset is too large")
+ return
+ }
+ return parse(ttf, offset)
+ default:
+ err = FormatError("bad TTF version")
return
}
n := int(d.u16())

[brad...@golang.org]

LGTM


http://codereview.appspot.com/6194050/

[nige...@golang.org]

*** Submitted as
http://code.google.com/p/freetype-go/source/detail?r=5f15df395cc7 ***

freetype: support TrueType Collection files (.TTC files, as opposed to
.TTF files)

R=bradfitz
CC=golang-dev
http://codereview.appspot.com/6194050


http://codereview.appspot.com/6194050/