font/sfnt: add a Font.Name method.
Also make all of the Buffer fields non-exported. LoadGlyph now returns the segments instead of setting Buffer.Segments for the caller to use. Change-Id: I3f87070da5e8f014f88dbca70b62a4cd30e3fd66 Reviewed-on: https://go-review.googlesource.com/34532 Reviewed-by: Dave Day <djd@golang.org>
This commit is contained in:
Nigel Tao
parent
ed90ab82a8
commit
2d771d3c32
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@ -19,6 +19,7 @@ import (
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"io"
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"golang.org/x/image/math/fixed"
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"golang.org/x/text/encoding/charmap"
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)
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// These constants are not part of the specifications, but are limitations used
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@ -34,22 +35,26 @@ const (
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)
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var (
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errGlyphIndexOutOfRange = errors.New("sfnt: glyph index out of range")
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// ErrNotFound indicates that the requested value was not found.
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ErrNotFound = errors.New("sfnt: not found")
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errInvalidBounds = errors.New("sfnt: invalid bounds")
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errInvalidCFFTable = errors.New("sfnt: invalid CFF table")
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errInvalidHeadTable = errors.New("sfnt: invalid head table")
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errInvalidLocationData = errors.New("sfnt: invalid location data")
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errInvalidMaxpTable = errors.New("sfnt: invalid maxp table")
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errInvalidNameTable = errors.New("sfnt: invalid name table")
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errInvalidSourceData = errors.New("sfnt: invalid source data")
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errInvalidTableOffset = errors.New("sfnt: invalid table offset")
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errInvalidTableTagOrder = errors.New("sfnt: invalid table tag order")
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errInvalidUCS2String = errors.New("sfnt: invalid UCS-2 string")
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errInvalidVersion = errors.New("sfnt: invalid version")
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errUnsupportedCFFVersion = errors.New("sfnt: unsupported CFF version")
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errUnsupportedRealNumberEncoding = errors.New("sfnt: unsupported real number encoding")
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errUnsupportedNumberOfHints = errors.New("sfnt: unsupported number of hints")
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errUnsupportedNumberOfTables = errors.New("sfnt: unsupported number of tables")
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errUnsupportedPlatformEncoding = errors.New("sfnt: unsupported platform encoding")
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errUnsupportedTableOffsetLength = errors.New("sfnt: unsupported table offset or length")
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errUnsupportedType2Charstring = errors.New("sfnt: unsupported Type 2 Charstring")
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)
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@ -57,12 +62,57 @@ var (
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// GlyphIndex is a glyph index in a Font.
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type GlyphIndex uint16
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// NameID identifies a name table entry.
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//
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// See the "Name IDs" section of
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// https://www.microsoft.com/typography/otspec/name.htm
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type NameID uint16
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const (
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NameIDCopyright NameID = 0
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NameIDFamily = 1
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NameIDSubfamily = 2
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NameIDUniqueIdentifier = 3
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NameIDFull = 4
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NameIDVersion = 5
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NameIDPostScript = 6
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NameIDTrademark = 7
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NameIDManufacturer = 8
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NameIDDesigner = 9
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NameIDDescription = 10
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NameIDVendorURL = 11
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NameIDDesignerURL = 12
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NameIDLicense = 13
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NameIDLicenseURL = 14
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NameIDTypographicFamily = 16
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NameIDTypographicSubfamily = 17
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NameIDCompatibleFull = 18
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NameIDSampleText = 19
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NameIDPostScriptCID = 20
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NameIDWWSFamily = 21
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NameIDWWSSubfamily = 22
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NameIDLightBackgroundPalette = 23
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NameIDDarkBackgroundPalette = 24
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NameIDVariationsPostScriptPrefix = 25
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)
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// Units are an integral number of abstract, scalable "font units". The em
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// square is typically 1000 or 2048 "font units". This would map to a certain
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// number (e.g. 30 pixels) of physical pixels, depending on things like the
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// display resolution (DPI) and font size (e.g. a 12 point font).
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type Units int32
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// Platform IDs and Platform Specific IDs as per
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// https://www.microsoft.com/typography/otspec/name.htm
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const (
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pidMacintosh = 1
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pidWindows = 3
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psidMacintoshRoman = 0
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psidWindowsUCS2 = 1
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)
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func u16(b []byte) uint16 {
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_ = b[1] // Bounds check hint to compiler.
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return uint16(b[0])<<8 | uint16(b[1])<<0
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@ -178,10 +228,20 @@ func ParseReaderAt(src io.ReaderAt) (*Font, error) {
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// Font is an SFNT font.
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//
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// All of its methods are safe to call concurrently, although the method
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// arguments may have further restrictions. For example, it is valid to have
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// multiple concurrent Font.LoadGlyph calls to the same *Font receiver, as long
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// as each call has a different Buffer.
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// Many of its methods take a *Buffer argument, as re-using buffers can reduce
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// the total memory allocation of repeated Font method calls, such as measuring
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// and rasterizing every unique glyph in a string of text. If efficiency is not
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// a concern, passing a nil *Buffer is valid, and implies using a temporary
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// buffer for a single call.
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//
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// It is valid to re-use a *Buffer with multiple Font method calls, even with
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// different *Font receivers, as long as they are not concurrent calls.
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//
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// All of the Font methods are safe to call concurrently, as long as each call
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// has a different *Buffer (or nil).
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//
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// The Font methods that don't take a *Buffer argument are always safe to call
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// concurrently.
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type Font struct {
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src source
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@ -369,14 +429,14 @@ func (f *Font) initialize() error {
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// TODO: func (f *Font) GlyphIndex(r rune) (x GlyphIndex, ok bool)
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// This will require parsing the cmap table.
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func (f *Font) viewGlyphData(buf []byte, x GlyphIndex) ([]byte, error) {
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func (f *Font) viewGlyphData(b *Buffer, x GlyphIndex) ([]byte, error) {
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xx := int(x)
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if f.NumGlyphs() <= xx {
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return nil, errGlyphIndexOutOfRange
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return nil, ErrNotFound
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}
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i := f.cached.locations[xx+0]
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j := f.cached.locations[xx+1]
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return f.src.view(buf, int(i), int(j-i))
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return b.view(&f.src, int(i), int(j-i))
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}
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// LoadGlyphOptions are the options to the Font.LoadGlyph method.
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@ -384,48 +444,145 @@ type LoadGlyphOptions struct {
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// TODO: scale / transform / hinting.
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}
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// LoadGlyph loads the glyphs vectors for the x'th glyph into b.Segments.
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func (f *Font) LoadGlyph(b *Buffer, x GlyphIndex, opts *LoadGlyphOptions) error {
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buf, err := f.viewGlyphData(b.buf, x)
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if err != nil {
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return err
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}
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// Only update b.buf if it is safe to re-use buf.
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if f.src.viewBufferWritable() {
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b.buf = buf
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}
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b.Segments = b.Segments[:0]
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if f.cached.isPostScript {
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b.psi.type2Charstrings.initialize(b.Segments)
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if err := b.psi.run(psContextType2Charstring, buf); err != nil {
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return err
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}
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b.Segments = b.psi.type2Charstrings.segments
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} else {
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return errors.New("sfnt: TODO: load glyf data")
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}
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// TODO: look at opts to scale / transform / hint the Buffer.Segments.
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return nil
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}
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// Buffer holds the result of the Font.LoadGlyph method. It is valid to re-use
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// a Buffer with multiple Font.LoadGlyph calls, even with different *Font
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// receivers, as long as they are not concurrent calls.
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// LoadGlyph returns the vector segments for the x'th glyph.
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//
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// It is also valid to have multiple concurrent Font.LoadGlyph calls to the
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// same *Font receiver, as long as each call has a different Buffer.
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// If b is non-nil, the segments become invalid to use once b is re-used.
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//
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// It returns ErrNotFound if the glyph index is out of range.
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func (f *Font) LoadGlyph(b *Buffer, x GlyphIndex, opts *LoadGlyphOptions) ([]Segment, error) {
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if b == nil {
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b = &Buffer{}
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}
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buf, err := f.viewGlyphData(b, x)
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if err != nil {
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return nil, err
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}
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b.segments = b.segments[:0]
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if f.cached.isPostScript {
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b.psi.type2Charstrings.initialize(b.segments)
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if err := b.psi.run(psContextType2Charstring, buf); err != nil {
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return nil, err
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}
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b.segments = b.psi.type2Charstrings.segments
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} else {
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return nil, errors.New("sfnt: TODO: load glyf data")
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}
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// TODO: look at opts to scale / transform / hint the Buffer.segments.
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return b.segments, nil
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}
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// Name returns the name value keyed by the given NameID.
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//
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// It returns ErrNotFound if there is no value for that key.
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func (f *Font) Name(b *Buffer, id NameID) (string, error) {
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if b == nil {
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b = &Buffer{}
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}
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const headerSize, entrySize = 6, 12
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if f.name.length < headerSize {
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return "", errInvalidNameTable
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}
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buf, err := b.view(&f.src, int(f.name.offset), headerSize)
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if err != nil {
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return "", err
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}
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nSubtables := u16(buf[2:])
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if f.name.length < headerSize+entrySize*uint32(nSubtables) {
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return "", errInvalidNameTable
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}
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stringOffset := u16(buf[4:])
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seen := false
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for i, n := 0, int(nSubtables); i < n; i++ {
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buf, err := b.view(&f.src, int(f.name.offset)+headerSize+entrySize*i, entrySize)
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if err != nil {
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return "", err
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}
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if u16(buf[6:]) != uint16(id) {
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continue
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}
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seen = true
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var stringify func([]byte) (string, error)
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switch u32(buf) {
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default:
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continue
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case pidMacintosh<<16 | psidMacintoshRoman:
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stringify = stringifyMacintosh
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case pidWindows<<16 | psidWindowsUCS2:
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stringify = stringifyUCS2
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}
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nameLength := u16(buf[8:])
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nameOffset := u16(buf[10:])
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buf, err = b.view(&f.src, int(f.name.offset)+int(nameOffset)+int(stringOffset), int(nameLength))
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if err != nil {
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return "", err
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}
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return stringify(buf)
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}
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if seen {
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return "", errUnsupportedPlatformEncoding
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}
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return "", ErrNotFound
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}
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func stringifyMacintosh(b []byte) (string, error) {
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for _, c := range b {
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if c >= 0x80 {
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// b contains some non-ASCII bytes.
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s, _ := charmap.Macintosh.NewDecoder().Bytes(b)
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return string(s), nil
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}
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}
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// b contains only ASCII bytes.
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return string(b), nil
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}
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func stringifyUCS2(b []byte) (string, error) {
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if len(b)&1 != 0 {
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return "", errInvalidUCS2String
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}
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r := make([]rune, len(b)/2)
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for i := range r {
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r[i] = rune(u16(b))
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b = b[2:]
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}
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return string(r), nil
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}
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// Buffer holds re-usable buffers that can reduce the total memory allocation
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// of repeated Font method calls.
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//
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// See the Font type's documentation comment for more details.
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type Buffer struct {
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Segments []Segment
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// buf is a byte buffer for when a Font's source is an io.ReaderAt.
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buf []byte
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// segments holds glyph vector path segments.
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segments []Segment
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// psi is a PostScript interpreter for when the Font is an OpenType/CFF
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// font.
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psi psInterpreter
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}
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func (b *Buffer) view(src *source, offset, length int) ([]byte, error) {
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buf, err := src.view(b.buf, offset, length)
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if err != nil {
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return nil, err
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}
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// Only update b.buf if it is safe to re-use buf.
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if src.viewBufferWritable() {
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b.buf = buf
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}
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return buf, nil
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}
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// Segment is a segment of a vector path.
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type Segment struct {
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Op SegmentOp
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@ -166,11 +166,11 @@ func TestPostScript(t *testing.T) {
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var b Buffer
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loop:
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for i, want := range wants {
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if err := f.LoadGlyph(&b, GlyphIndex(i), nil); err != nil {
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got, err := f.LoadGlyph(&b, GlyphIndex(i), nil)
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if err != nil {
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t.Errorf("i=%d: LoadGlyph: %v", i, err)
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continue
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}
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got := b.Segments
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if len(got) != len(want) {
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t.Errorf("i=%d: got %d elements, want %d\noverall:\ngot %v\nwant %v",
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i, len(got), len(want), got, want)
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@ -184,4 +184,14 @@ loop:
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}
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}
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}
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if _, err := f.LoadGlyph(nil, 0xffff, nil); err != ErrNotFound {
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t.Errorf("LoadGlyph(..., 0xffff, ...):\ngot %v\nwant %v", err, ErrNotFound)
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}
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name, err := f.Name(nil, NameIDFamily)
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if err != nil {
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t.Errorf("Name: %v", err)
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} else if want := "CFFTest"; name != want {
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t.Errorf("Name:\ngot %q\nwant %q", name, want)
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}
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}
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