feat: support customize title

title.go

@@ -0,0 +1,96 @@
+// MIT License
+
+// Copyright (c) 2021 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 (
+	"strconv"
+	"strings"
+
+	"github.com/wcharczuk/go-chart/v2"
+)
+
+type titleMeasureOption struct {
+	width  int
+	height int
+	text   string
+}
+
+func NewTitleCustomize(title Title) chart.Renderable {
+	return func(r chart.Renderer, cb chart.Box, chartDefaults chart.Style) {
+		if len(title.Text) == 0 || title.Style.Hidden {
+			return
+		}
+		if title.Font != nil {
+			r.SetFont(title.Font)
+		}
+		r.SetFontColor(title.Style.FontColor)
+		titleFontSize := title.Style.GetFontSize(chart.DefaultTitleFontSize)
+		r.SetFontSize(titleFontSize)
+
+		arr := strings.Split(title.Text, "\n")
+		textWidth := 0
+		textHeight := 0
+		measureOptions := make([]titleMeasureOption, len(arr))
+		for index, str := range arr {
+			textBox := r.MeasureText(str)
+
+			w := textBox.Width()
+			h := textBox.Height()
+			if w > textWidth {
+				textWidth = w
+			}
+			if h > textHeight {
+				textHeight = h
+			}
+			measureOptions[index] = titleMeasureOption{
+				text:   str,
+				width:  w,
+				height: h,
+			}
+		}
+
+		titleX := 0
+		switch title.Left {
+		case "right":
+			titleX = cb.Left + cb.Width() - textWidth
+		case "center":
+			titleX = cb.Left + cb.Width()>>1 - (textWidth >> 1)
+		default:
+			if strings.HasSuffix(title.Left, "%") {
+				value, _ := strconv.Atoi(strings.ReplaceAll(title.Left, "%", ""))
+				titleX = cb.Left + cb.Width()*value/100
+			} else {
+				value, _ := strconv.Atoi(title.Left)
+				titleX = cb.Left + value
+			}
+		}
+
+		titleY := cb.Top + title.Style.Padding.GetTop(chart.DefaultTitleTop) + (textHeight >> 1)
+
+		for _, item := range measureOptions {
+			x := titleX + (textWidth-item.width)>>1
+			r.Text(item.text, x, titleY)
+			titleY += textHeight
+		}
+	}
+}