Add Font.Name method.
This commit is contained in:
Stephen Edwards
Nigel Tao
parent
fb514f71f0
commit
995030b974
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@ -26,6 +26,41 @@ import (
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// An Index is a Font's index of a rune.
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type Index uint16
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// A NameID represents the Name Identifiers in the name table.
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type NameID uint16
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const (
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NameIDCopyright NameID = 0
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NameIDFontFamily = 1
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NameIDFontSubfamily = 2
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NameIDUniqueSubfamilyID = 3
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NameIDFontFullName = 4
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NameIDNameTableVersion = 5
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NameIDPostscriptName = 6
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NameIDTrademarkNotice = 7
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NameIDManufacturerName = 8
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NameIDDesignerName = 9
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NameIDFontDescription = 10
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NameIDFontVendorURL = 11
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NameIDFontDesignerURL = 12
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NameIDFontLicense = 13
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NameIDFontLicenseURL = 14
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NameIDPreferredFamily = 16
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NameIDPreferredSubfamily = 17
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NameIDCompatibleName = 18
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NameIDSampleText = 19
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)
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const (
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// A 32-bit encoding consists of a most-significant 16-bit Platform ID and a
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// least-significant 16-bit Platform Specific ID. The magic numbers are
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// specified at https://www.microsoft.com/typography/otspec/name.htm
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unicodeEncoding = 0x00000003 // PID = 0 (Unicode), PSID = 3 (Unicode 2.0)
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microsoftSymbolEncoding = 0x00030000 // PID = 3 (Microsoft), PSID = 0 (Symbol)
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microsoftUCS2Encoding = 0x00030001 // PID = 3 (Microsoft), PSID = 1 (UCS-2)
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microsoftUCS4Encoding = 0x0003000a // PID = 3 (Microsoft), PSID = 10 (UCS-4)
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)
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// An HMetric holds the horizontal metrics of a single glyph.
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type HMetric struct {
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AdvanceWidth, LeftSideBearing fixed.Int26_6
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@ -78,6 +113,43 @@ func readTable(ttf []byte, offsetLength []byte) ([]byte, error) {
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return ttf[offset:end], nil
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}
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// parseSubtables wraps the commonality in Name and parseCmap.
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func parseSubtables(b []byte, name string, offset, size int, tableCheckPred func(b []byte) bool) (int, int, error) {
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if len(b) < 4 {
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return 0, 0, FormatError(name + " too short")
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}
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nsubtab := int(u16(b, 2))
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if len(b) < size*nsubtab+offset {
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return 0, 0, FormatError(name + " too short")
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}
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pid, x := 0, offset
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offset = 0
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for i := 0; i < nsubtab; i, x = i+1, x+size {
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if tableCheckPred != nil && !tableCheckPred(b[x:]) { // When tableCheck is nil, examine the table.
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continue
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}
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// We read the 16-bit Platform ID and 16-bit Platform Specific ID as a single uint32.
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// All values are big-endian.
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pidPsid := u32(b, x)
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// We prefer the Unicode cmap encoding. Failing to find that, we fall
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// back onto the Microsoft cmap encoding.
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if pidPsid == unicodeEncoding {
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offset, pid = x, int(pidPsid>>16)
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break
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} else if pidPsid == microsoftSymbolEncoding ||
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pidPsid == microsoftUCS2Encoding ||
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pidPsid == microsoftUCS4Encoding {
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offset, pid = x, int(pidPsid>>16)
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// We don't break out of the for loop, so that Unicode can override Microsoft.
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}
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}
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return offset, pid, nil
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}
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const (
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locaOffsetFormatUnknown int = iota
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locaOffsetFormatShort
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@ -93,7 +165,7 @@ type cm struct {
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type Font struct {
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// Tables sliced from the TTF data. The different tables are documented
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// at http://developer.apple.com/fonts/TTRefMan/RM06/Chap6.html
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cmap, cvt, fpgm, glyf, hdmx, head, hhea, hmtx, kern, loca, maxp, os2, prep, vmtx []byte
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cmap, cvt, fpgm, glyf, hdmx, head, hhea, hmtx, kern, loca, maxp, name, os2, prep, vmtx []byte
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cmapIndexes []byte
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@ -112,45 +184,12 @@ func (f *Font) parseCmap() error {
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cmapFormat4 = 4
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cmapFormat12 = 12
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languageIndependent = 0
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// A 32-bit encoding consists of a most-significant 16-bit Platform ID and a
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// least-significant 16-bit Platform Specific ID. The magic numbers are
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// specified at https://www.microsoft.com/typography/otspec/name.htm
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unicodeEncoding = 0x00000003 // PID = 0 (Unicode), PSID = 3 (Unicode 2.0)
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microsoftSymbolEncoding = 0x00030000 // PID = 3 (Microsoft), PSID = 0 (Symbol)
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microsoftUCS2Encoding = 0x00030001 // PID = 3 (Microsoft), PSID = 1 (UCS-2)
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microsoftUCS4Encoding = 0x0003000a // PID = 3 (Microsoft), PSID = 10 (UCS-4)
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)
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if len(f.cmap) < 4 {
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return FormatError("cmap too short")
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}
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nsubtab := int(u16(f.cmap, 2))
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if len(f.cmap) < 8*nsubtab+4 {
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return FormatError("cmap too short")
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}
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offset, found, x := 0, false, 4
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for i := 0; i < nsubtab; i++ {
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// We read the 16-bit Platform ID and 16-bit Platform Specific ID as a single uint32.
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// All values are big-endian.
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pidPsid, o := u32(f.cmap, x), u32(f.cmap, x+4)
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x += 8
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// We prefer the Unicode cmap encoding. Failing to find that, we fall
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// back onto the Microsoft cmap encoding.
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if pidPsid == unicodeEncoding {
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offset, found = int(o), true
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break
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} else if pidPsid == microsoftSymbolEncoding ||
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pidPsid == microsoftUCS2Encoding ||
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pidPsid == microsoftUCS4Encoding {
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offset, found = int(o), true
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// We don't break out of the for loop, so that Unicode can override Microsoft.
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}
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}
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if !found {
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return UnsupportedError("cmap encoding")
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x, _, err := parseSubtables(f.cmap, "cmap", 4, 8, nil)
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offset := int(u32(f.cmap, x+4))
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if err != nil {
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return err
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}
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if offset <= 0 || offset > len(f.cmap) {
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return FormatError("bad cmap offset")
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@ -345,6 +384,48 @@ func (f *Font) Index(x rune) Index {
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return 0
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}
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// Name returns the NameID value of a Font.
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// Returns "" on error or not found.
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func (f *Font) Name(id NameID) string {
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x, platformID, err := parseSubtables(f.name, "name", 6, 12, func(b []byte) bool {
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return NameID(u16(b, 6)) == id
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})
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if err != nil {
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return ""
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}
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offset, length := u16(f.name, x+10), u16(f.name, x+8)
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offset += u16(f.name, 4)
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// Return the ASCII value of the encoded string.
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// The string is encoded as UTF-16 on non-Apple platformIDs; Apple is platformID 1.
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src := f.name[offset : offset+length]
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var dst []byte
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if platformID != 1 { // UTF-16.
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if len(src)&1 != 0 {
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return ""
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}
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dst = make([]byte, len(src)/2)
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for i := range dst {
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dst[i] = printable(u16(src, 2*i))
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}
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} else { // ASCII.
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dst = make([]byte, len(src))
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for i, c := range src {
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dst[i] = printable(uint16(c))
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}
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}
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return string(dst)
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}
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func printable(r uint16) byte {
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if 0x20 <= r && r <= 0x7f {
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return byte(r)
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}
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return '?'
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}
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// unscaledHMetric returns the unscaled horizontal metrics for the glyph with
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// the given index.
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func (f *Font) unscaledHMetric(i Index) (h HMetric) {
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@ -518,6 +599,8 @@ func parse(ttf []byte, offset int) (font *Font, err error) {
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f.loca, err = readTable(ttf, ttf[x+8:x+16])
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case "maxp":
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f.maxp, err = readTable(ttf, ttf[x+8:x+16])
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case "name":
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f.name, err = readTable(ttf, ttf[x+8:x+16])
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case "OS/2":
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f.os2, err = readTable(ttf, ttf[x+8:x+16])
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case "prep":
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@ -211,6 +211,29 @@ func TestIndex(t *testing.T) {
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}
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}
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func TestName(t *testing.T) {
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testCases := map[string]string{
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"luximr": "Luxi Mono",
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"luxirr": "Luxi Serif",
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"luxisr": "Luxi Sans",
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}
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for name, want := range testCases {
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f, testdataIsOptional, err := parseTestdataFont(name)
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if err != nil {
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if testdataIsOptional {
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t.Log(err)
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} else {
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t.Fatal(err)
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}
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continue
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}
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if got := f.Name(NameIDFontFamily); got != want {
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t.Errorf("%s: got %q, want %q", name, got, want)
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}
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}
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}
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type scalingTestData struct {
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advanceWidth fixed.Int26_6
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bounds fixed.Rectangle26_6
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