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font.go
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font.go
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package charts
import (
"fmt"
"sync"
"github.com/golang/freetype/truetype"
"github.com/wcharczuk/go-chart/v2/roboto"
)
const defaultFontSize = 12.0
var fonts = sync.Map{}
var defaultFontFamily = "default"
func init() {
name := "roboto"
if err := InstallFont(name, roboto.Roboto); err != nil {
panic(fmt.Errorf("could not install default font - %v", err))
} else if err = SetDefaultFont(name); err != nil {
panic(fmt.Errorf("could not set default font - %v", err))
}
}
// InstallFont installs the font for charts
func InstallFont(fontFamily string, data []byte) error {
font, err := truetype.Parse(data)
if err != nil {
return err
}
fonts.Store(fontFamily, font)
return nil
}
func getPreferredFont(f ...*truetype.Font) *truetype.Font {
for _, font := range f {
if font != nil {
return font
}
}
return GetDefaultFont()
}
// GetDefaultFont get default font.
func GetDefaultFont() *truetype.Font {
return GetFont(defaultFontFamily)
}
// SetDefaultFont set default font by name.
func SetDefaultFont(fontFamily string) error {
if value, ok := fonts.Load(fontFamily); ok {
fonts.Store(defaultFontFamily, value)
return nil
}
return fmt.Errorf("font not found: %v", fontFamily)
}
// GetFont get the font by font family or the default if the family is not installed.
func GetFont(fontFamily string) *truetype.Font {
if value, ok := fonts.Load(fontFamily); ok {
if f, ok := value.(*truetype.Font); ok {
return f
}
}
return GetDefaultFont()
}