feat: support install font and enhance title padding

font.go

@@ -0,0 +1,61 @@
+// MIT License
+
+// Copyright (c) 2022 Tree Xie
+
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+
+package charts
+
+import (
+	"errors"
+	"sync"
+
+	"github.com/golang/freetype/truetype"
+	"github.com/wcharczuk/go-chart/v2/roboto"
+)
+
+var fonts = sync.Map{}
+var ErrFontNotExists = errors.New("font is not exists")
+
+func init() {
+	_ = InstallFont("roboto", roboto.Roboto)
+}
+
+// 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
+}
+
+// GetFont get the font by font family
+func GetFont(fontFamily string) (*truetype.Font, error) {
+	value, ok := fonts.Load(fontFamily)
+	if !ok {
+		return nil, ErrFontNotExists
+	}
+	f, ok := value.(*truetype.Font)
+	if !ok {
+		return nil, ErrFontNotExists
+	}
+	return f, nil
+}