260 lines
6.5 KiB
Go
260 lines
6.5 KiB
Go
// Copyright 2017 The Go Authors. All rights reserved.
|
|
// Use of this source code is governed by a BSD-style
|
|
// license that can be found in the LICENSE file.
|
|
|
|
package sfnt
|
|
|
|
import (
|
|
"golang.org/x/text/encoding/charmap"
|
|
)
|
|
|
|
// Platform IDs and Platform Specific IDs as per
|
|
// https://www.microsoft.com/typography/otspec/name.htm
|
|
const (
|
|
pidUnicode = 0
|
|
pidMacintosh = 1
|
|
pidWindows = 3
|
|
|
|
psidUnicode2BMPOnly = 3
|
|
psidUnicode2FullRepertoire = 4
|
|
// Note that FontForge may generate a bogus Platform Specific ID (value 10)
|
|
// for the Unicode Platform ID (value 0). See
|
|
// https://github.com/fontforge/fontforge/issues/2728
|
|
|
|
psidMacintoshRoman = 0
|
|
|
|
psidWindowsSymbol = 0
|
|
psidWindowsUCS2 = 1
|
|
psidWindowsUCS4 = 10
|
|
)
|
|
|
|
// platformEncodingWidth returns the number of bytes per character assumed by
|
|
// the given Platform ID and Platform Specific ID.
|
|
//
|
|
// Very old fonts, from before Unicode was widely adopted, assume only 1 byte
|
|
// per character: a character map.
|
|
//
|
|
// Old fonts, from when Unicode meant the Basic Multilingual Plane (BMP),
|
|
// assume that 2 bytes per character is sufficient.
|
|
//
|
|
// Recent fonts naturally support the full range of Unicode code points, which
|
|
// can take up to 4 bytes per character. Such fonts might still choose one of
|
|
// the legacy encodings if e.g. their repertoire is limited to the BMP, for
|
|
// greater compatibility with older software, or because the resultant file
|
|
// size can be smaller.
|
|
func platformEncodingWidth(pid, psid uint16) int {
|
|
switch pid {
|
|
case pidUnicode:
|
|
switch psid {
|
|
case psidUnicode2BMPOnly:
|
|
return 2
|
|
case psidUnicode2FullRepertoire:
|
|
return 4
|
|
}
|
|
|
|
case pidMacintosh:
|
|
switch psid {
|
|
case psidMacintoshRoman:
|
|
return 1
|
|
}
|
|
|
|
case pidWindows:
|
|
switch psid {
|
|
case psidWindowsSymbol:
|
|
return 2
|
|
case psidWindowsUCS2:
|
|
return 2
|
|
case psidWindowsUCS4:
|
|
return 4
|
|
}
|
|
}
|
|
return 0
|
|
}
|
|
|
|
// The various cmap formats are described at
|
|
// https://www.microsoft.com/typography/otspec/cmap.htm
|
|
|
|
var supportedCmapFormat = func(format, pid, psid uint16) bool {
|
|
switch format {
|
|
case 0:
|
|
return pid == pidMacintosh && psid == psidMacintoshRoman
|
|
case 4:
|
|
return true
|
|
case 12:
|
|
return true
|
|
}
|
|
return false
|
|
}
|
|
|
|
func (f *Font) makeCachedGlyphIndex(buf []byte, offset, length uint32, format uint16) ([]byte, glyphIndexFunc, error) {
|
|
switch format {
|
|
case 0:
|
|
return f.makeCachedGlyphIndexFormat0(buf, offset, length)
|
|
case 4:
|
|
return f.makeCachedGlyphIndexFormat4(buf, offset, length)
|
|
case 12:
|
|
return f.makeCachedGlyphIndexFormat12(buf, offset, length)
|
|
}
|
|
panic("unreachable")
|
|
}
|
|
|
|
func (f *Font) makeCachedGlyphIndexFormat0(buf []byte, offset, length uint32) ([]byte, glyphIndexFunc, error) {
|
|
if length != 6+256 || offset+length > f.cmap.length {
|
|
return nil, nil, errInvalidCmapTable
|
|
}
|
|
var err error
|
|
buf, err = f.src.view(buf, int(f.cmap.offset+offset), int(length))
|
|
if err != nil {
|
|
return nil, nil, err
|
|
}
|
|
var table [256]byte
|
|
copy(table[:], buf[6:])
|
|
return buf, func(f *Font, b *Buffer, r rune) (GlyphIndex, error) {
|
|
x, ok := charmap.Macintosh.EncodeRune(r)
|
|
if !ok {
|
|
// The source rune r is not representable in the Macintosh-Roman encoding.
|
|
return 0, nil
|
|
}
|
|
return GlyphIndex(table[x]), nil
|
|
}, nil
|
|
}
|
|
|
|
func (f *Font) makeCachedGlyphIndexFormat4(buf []byte, offset, length uint32) ([]byte, glyphIndexFunc, error) {
|
|
const headerSize = 14
|
|
if offset+headerSize > f.cmap.length {
|
|
return nil, nil, errInvalidCmapTable
|
|
}
|
|
var err error
|
|
buf, err = f.src.view(buf, int(f.cmap.offset+offset), headerSize)
|
|
if err != nil {
|
|
return nil, nil, err
|
|
}
|
|
offset += headerSize
|
|
|
|
segCount := u16(buf[6:])
|
|
if segCount&1 != 0 {
|
|
return nil, nil, errInvalidCmapTable
|
|
}
|
|
segCount /= 2
|
|
if segCount > maxCmapSegments {
|
|
return nil, nil, errUnsupportedNumberOfCmapSegments
|
|
}
|
|
|
|
eLength := 8*uint32(segCount) + 2
|
|
if offset+eLength > f.cmap.length {
|
|
return nil, nil, errInvalidCmapTable
|
|
}
|
|
buf, err = f.src.view(buf, int(f.cmap.offset+offset), int(eLength))
|
|
if err != nil {
|
|
return nil, nil, err
|
|
}
|
|
offset += eLength
|
|
|
|
entries := make([]cmapEntry16, segCount)
|
|
for i := range entries {
|
|
entries[i] = cmapEntry16{
|
|
end: u16(buf[0*len(entries)+0+2*i:]),
|
|
start: u16(buf[2*len(entries)+2+2*i:]),
|
|
delta: u16(buf[4*len(entries)+2+2*i:]),
|
|
offset: u16(buf[6*len(entries)+2+2*i:]),
|
|
}
|
|
}
|
|
indexesBase := f.cmap.offset + offset
|
|
indexesLength := f.cmap.length - offset
|
|
|
|
return buf, func(f *Font, b *Buffer, r rune) (GlyphIndex, error) {
|
|
if uint32(r) > 0xffff {
|
|
return 0, nil
|
|
}
|
|
|
|
c := uint16(r)
|
|
for i, j := 0, len(entries); i < j; {
|
|
h := i + (j-i)/2
|
|
entry := &entries[h]
|
|
if c < entry.start {
|
|
j = h
|
|
} else if entry.end < c {
|
|
i = h + 1
|
|
} else if entry.offset == 0 {
|
|
return GlyphIndex(c + entry.delta), nil
|
|
} else {
|
|
offset := uint32(entry.offset) + 2*uint32(h-len(entries)+int(c-entry.start))
|
|
if offset > indexesLength || offset+2 > indexesLength {
|
|
return 0, errInvalidCmapTable
|
|
}
|
|
x, err := b.view(&f.src, int(indexesBase+offset), 2)
|
|
if err != nil {
|
|
return 0, err
|
|
}
|
|
return GlyphIndex(u16(x)), nil
|
|
}
|
|
}
|
|
return 0, nil
|
|
}, nil
|
|
}
|
|
|
|
func (f *Font) makeCachedGlyphIndexFormat12(buf []byte, offset, _ uint32) ([]byte, glyphIndexFunc, error) {
|
|
const headerSize = 16
|
|
if offset+headerSize > f.cmap.length {
|
|
return nil, nil, errInvalidCmapTable
|
|
}
|
|
var err error
|
|
buf, err = f.src.view(buf, int(f.cmap.offset+offset), headerSize)
|
|
if err != nil {
|
|
return nil, nil, err
|
|
}
|
|
length := u32(buf[4:])
|
|
if f.cmap.length < offset || length > f.cmap.length-offset {
|
|
return nil, nil, errInvalidCmapTable
|
|
}
|
|
offset += headerSize
|
|
|
|
numGroups := u32(buf[12:])
|
|
if numGroups > maxCmapSegments {
|
|
return nil, nil, errUnsupportedNumberOfCmapSegments
|
|
}
|
|
|
|
eLength := 12 * numGroups
|
|
if headerSize+eLength != length {
|
|
return nil, nil, errInvalidCmapTable
|
|
}
|
|
buf, err = f.src.view(buf, int(f.cmap.offset+offset), int(eLength))
|
|
if err != nil {
|
|
return nil, nil, err
|
|
}
|
|
offset += eLength
|
|
|
|
entries := make([]cmapEntry32, numGroups)
|
|
for i := range entries {
|
|
entries[i] = cmapEntry32{
|
|
start: u32(buf[0+12*i:]),
|
|
end: u32(buf[4+12*i:]),
|
|
delta: u32(buf[8+12*i:]),
|
|
}
|
|
}
|
|
|
|
return buf, func(f *Font, b *Buffer, r rune) (GlyphIndex, error) {
|
|
c := uint32(r)
|
|
for i, j := 0, len(entries); i < j; {
|
|
h := i + (j-i)/2
|
|
entry := &entries[h]
|
|
if c < entry.start {
|
|
j = h
|
|
} else if entry.end < c {
|
|
i = h + 1
|
|
} else {
|
|
return GlyphIndex(c - entry.start + entry.delta), nil
|
|
}
|
|
}
|
|
return 0, nil
|
|
}, nil
|
|
}
|
|
|
|
type cmapEntry16 struct {
|
|
end, start, delta, offset uint16
|
|
}
|
|
|
|
type cmapEntry32 struct {
|
|
start, end, delta uint32
|
|
}
|