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Fix some style nits.

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This commit is contained in:
Nigel Tao 2015-09-21 17:13:27 +10:00
parent 995030b974
commit 640edd0946
1 changed files with 32 additions and 26 deletions
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58
truetype/truetype.go
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@ -26,7 +26,9 @@ import (
// An Index is a Font's index of a rune.
type Index uint16
// A NameID represents the Name Identifiers in the name table.
// A NameID identifies a name table entry.
//
// See https://developer.apple.com/fonts/TrueType-Reference-Manual/RM06/Chap6name.html
type NameID uint16
const (
@ -113,41 +115,49 @@ func readTable(ttf []byte, offsetLength []byte) ([]byte, error) {
return ttf[offset:end], nil
}
// parseSubtables wraps the commonality in Name and parseCmap.
func parseSubtables(b []byte, name string, offset, size int, tableCheckPred func(b []byte) bool) (int, int, error) {
if len(b) < 4 {
// parseSubtables returns the offset and platformID of the best subtable in
// table, where best favors a Unicode cmap encoding, and failing that, a
// Microsoft cmap encoding. offset is the offset of the first subtable in
// table, and size is the size of each subtable.
//
// If pred is non-nil, then only subtables that satisfy that predicate will be
// considered.
func parseSubtables(table []byte, name string, offset, size int, pred func([]byte) bool) (
bestOffset int, bestPID uint32, retErr error) {
if len(table) < 4 {
return 0, 0, FormatError(name + " too short")
}
nsubtab := int(u16(b, 2))
if len(b) < size*nsubtab+offset {
nSubtables := int(u16(table, 2))
if len(table) < size*nSubtables+offset {
return 0, 0, FormatError(name + " too short")
}
pid, x := 0, offset
offset = 0
for i := 0; i < nsubtab; i, x = i+1, x+size {
if tableCheckPred != nil && !tableCheckPred(b[x:]) { // When tableCheck is nil, examine the table.
ok := false
for i := 0; i < nSubtables; i, offset = i+1, offset+size {
if pred != nil && !pred(table[offset:]) {
continue
}
// We read the 16-bit Platform ID and 16-bit Platform Specific ID as a single uint32.
// All values are big-endian.
pidPsid := u32(b, x)
pidPsid := u32(table, offset)
// We prefer the Unicode cmap encoding. Failing to find that, we fall
// back onto the Microsoft cmap encoding.
if pidPsid == unicodeEncoding {
offset, pid = x, int(pidPsid>>16)
bestOffset, bestPID, ok = offset, pidPsid>>16, true
break
} else if pidPsid == microsoftSymbolEncoding ||
pidPsid == microsoftUCS2Encoding ||
pidPsid == microsoftUCS4Encoding {
offset, pid = x, int(pidPsid>>16)
bestOffset, bestPID, ok = offset, pidPsid>>16, true
// We don't break out of the for loop, so that Unicode can override Microsoft.
}
}
return offset, pid, nil
if !ok {
return 0, 0, UnsupportedError(name + " encoding")
}
return bestOffset, bestPID, nil
}
const (
@ -186,11 +196,11 @@ func (f *Font) parseCmap() error {
languageIndependent = 0
)
x, _, err := parseSubtables(f.cmap, "cmap", 4, 8, nil)
offset := int(u32(f.cmap, x+4))
offset, _, err := parseSubtables(f.cmap, "cmap", 4, 8, nil)
if err != nil {
return err
}
offset = int(u32(f.cmap, offset+4))
if offset <= 0 || offset > len(f.cmap) {
return FormatError("bad cmap offset")
}
@ -384,8 +394,8 @@ func (f *Font) Index(x rune) Index {
return 0
}
// Name returns the NameID value of a Font.
// Returns "" on error or not found.
// Name returns the Font's name value for the given NameID. It returns "" if
// there was an error, or if that name was not found.
func (f *Font) Name(id NameID) string {
x, platformID, err := parseSubtables(f.name, "name", 6, 12, func(b []byte) bool {
return NameID(u16(b, 6)) == id
@ -393,10 +403,7 @@ func (f *Font) Name(id NameID) string {
if err != nil {
return ""
}
offset, length := u16(f.name, x+10), u16(f.name, x+8)
offset += u16(f.name, 4)
offset, length := u16(f.name, 4)+u16(f.name, x+10), u16(f.name, x+8)
// Return the ASCII value of the encoded string.
// The string is encoded as UTF-16 on non-Apple platformIDs; Apple is platformID 1.
src := f.name[offset : offset+length]
@ -415,12 +422,11 @@ func (f *Font) Name(id NameID) string {
dst[i] = printable(uint16(c))
}
}
return string(dst)
}
func printable(r uint16) byte {
if 0x20 <= r && r <= 0x7f {
if 0x20 <= r && r < 0x7f {
return byte(r)
}
return '?'