draw2d/font.go

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// Copyright 2010 The draw2d Authors. All rights reserved.
// created: 13/12/2010 by Laurent Le Goff
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package draw2d
import (
"io/ioutil"
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"log"
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"path/filepath"
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"github.com/golang/freetype/truetype"
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)
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// FontStyle defines bold and italic styles for the font
// It is possible to combine values for mixed styles, eg.
// FontData.Style = FontStyleBold | FontStyleItalic
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type FontStyle byte
const (
FontStyleNormal FontStyle = iota
FontStyleBold
FontStyleItalic
)
type FontFamily byte
const (
FontFamilySans FontFamily = iota
FontFamilySerif
FontFamilyMono
)
type FontData struct {
Name string
Family FontFamily
Style FontStyle
}
type FontFileNamer func(fontData FontData) string
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func FontFileName(fontData FontData) string {
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fontFileName := fontData.Name
switch fontData.Family {
case FontFamilySans:
fontFileName += "s"
case FontFamilySerif:
fontFileName += "r"
case FontFamilyMono:
fontFileName += "m"
}
if fontData.Style&FontStyleBold != 0 {
fontFileName += "b"
} else {
fontFileName += "r"
}
if fontData.Style&FontStyleItalic != 0 {
fontFileName += "i"
}
fontFileName += ".ttf"
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return fontFileName
}
func RegisterFont(fontData FontData, font *truetype.Font) {
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fontCache.Store(fontData, font)
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}
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func GetFont(fontData FontData) (font *truetype.Font) {
var err error
if font, err = fontCache.Load(fontData); err != nil {
log.Println(err)
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}
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return
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}
func GetFontFolder() string {
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return defaultFonts.folder
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}
func SetFontFolder(folder string) {
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defaultFonts.folder = filepath.Clean(folder)
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}
func SetFontNamer(fn FontFileNamer) {
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defaultFonts.namer = fn
}
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// Types implementing this interface can be passed to SetFontCache to change the
// way fonts are being stored and retrieved.
type FontCache interface {
// Loads a truetype font represented by the FontData object passed as
// argument.
// The method returns an error if the font could not be loaded, either
// because it didn't exist or the resource it was loaded from was corrupted.
Load(FontData) (*truetype.Font, error)
// Sets the truetype font that will be returned by Load when given the font
// data passed as first argument.
Store(FontData, *truetype.Font)
}
// Changes the font cache backend used by the package. After calling this
// functionSetFontFolder and SetFontNamer will not affect anymore how fonts are
// loaded.
// To restore the default font cache, call this function passing nil as argument.
func SetFontCache(cache FontCache) {
if cache == nil {
fontCache = defaultFonts
} else {
fontCache = cache
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}
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}
type defaultFontCache struct {
fonts map[string]*truetype.Font
folder string
namer FontFileNamer
}
func (cache *defaultFontCache) Load(fontData FontData) (font *truetype.Font, err error) {
if font = cache.fonts[cache.namer(fontData)]; font != nil {
return font, nil
}
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var data []byte
var file = cache.namer(fontData)
if data, err = ioutil.ReadFile(filepath.Join(cache.folder, file)); err != nil {
return
}
if font, err = truetype.Parse(data); err != nil {
return
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}
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cache.fonts[file] = font
return
}
func (cache *defaultFontCache) Store(fontData FontData, font *truetype.Font) {
cache.fonts[cache.namer(fontData)] = font
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}
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var (
defaultFonts = &defaultFontCache{
fonts: make(map[string]*truetype.Font),
folder: "../resource/font",
namer: FontFileName,
}
fontCache FontCache = defaultFonts
)