go-charts/axis.go

// 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 (
	"github.com/golang/freetype/truetype"
)

type axisPainter struct {
	p   *Painter
	opt *AxisOption
}

func NewAxisPainter(p *Painter, opt AxisOption) *axisPainter {
	return &axisPainter{
		p:   p,
		opt: &opt,
	}
}

type AxisOption struct {
	// The theme of chart
	Theme ColorPalette
	// The label of axis
	Data []string
	// The boundary gap on both sides of a coordinate axis.
	// Nil or *true means the center part of two axis ticks
	BoundaryGap *bool
	// The position of axis, it can be 'left', 'top', 'right' or 'bottom'
	Position string
	// Number of segments that the axis is split into. Note that this number serves only as a recommendation.
	SplitNumber int
	// The line color of axis
	StrokeColor Color
	// The line width
	StrokeWidth float64
	// The length of the axis tick
	TickLength int
	// The margin value of label
	LabelMargin int
	// The font size of label
	FontSize float64
	// The font of label
	Font *truetype.Font
	// The color of label
	FontColor Color
	// The flag for show axis split line, set this to true will show axis split line
	SplitLineShow bool
	// The color of split line
	SplitLineColor Color
}

func (a *axisPainter) Render() (Box, error) {
	opt := a.opt
	top := a.p
	theme := opt.Theme

	strokeWidth := opt.StrokeWidth
	if strokeWidth == 0 {
		strokeWidth = 1
	}

	font := opt.Font
	if font == nil {
		font = theme.GetFont()
	}
	fontColor := opt.FontColor
	if fontColor.IsZero() {
		fontColor = theme.GetTextColor()
	}
	fontSize := opt.FontSize
	if fontSize == 0 {
		fontSize = theme.GetFontSize()
	}
	strokeColor := opt.StrokeColor
	if strokeColor.IsZero() {
		strokeColor = theme.GetAxisStrokeColor()
	}

	tickCount := opt.SplitNumber
	if tickCount == 0 {
		tickCount = len(opt.Data)
	}

	boundaryGap := true
	if opt.BoundaryGap != nil && !*opt.BoundaryGap {
		boundaryGap = false
	}
	isVertical := opt.Position == PositionLeft ||
		opt.Position == PositionRight

	labelPosition := ""
	if !boundaryGap {
		tickCount--
		labelPosition = PositionLeft
	}
	if isVertical && boundaryGap {
		labelPosition = PositionCenter
	}

	// TODO 计算unit
	unit := 1
	// 如果小于0，则表示不处理
	tickLength := getDefaultInt(opt.TickLength, 5)
	labelMargin := getDefaultInt(opt.LabelMargin, 5)

	style := Style{
		StrokeColor: strokeColor,
		StrokeWidth: strokeWidth,
		Font:        font,
		FontColor:   fontColor,
		FontSize:    fontSize,
	}
	top.SetDrawingStyle(style).OverrideTextStyle(style)

	textMaxWidth, textMaxHeight := top.MeasureTextMaxWidthHeight(opt.Data)

	width := 0
	height := 0
	// 垂直
	if isVertical {
		width = textMaxWidth + tickLength<<1
		height = top.Height()
	} else {
		width = top.Width()
		height = tickLength<<1 + textMaxHeight
	}
	padding := Box{}
	switch opt.Position {
	case PositionTop:
		padding.Top = top.Height() - height
	case PositionLeft:
		padding.Right = top.Width() - width
	case PositionRight:
		padding.Left = top.Width() - width
	default:
		padding.Top = top.Height() - defaultXAxisHeight
	}

	p := top.Child(PainterPaddingOption(padding))

	x0 := 0
	y0 := 0
	x1 := 0
	y1 := 0
	ticksPaddingTop := 0
	ticksPaddingLeft := 0
	labelPaddingTop := 0
	labelPaddingLeft := 0
	labelPaddingRight := 0
	orient := ""
	textAlign := ""

	switch opt.Position {
	case PositionTop:
		labelPaddingTop = labelMargin
		x1 = p.Width()
		y0 = labelMargin + int(opt.FontSize)
		ticksPaddingTop = int(opt.FontSize)
		y1 = y0
		orient = OrientHorizontal
	case PositionLeft:
		x0 = p.Width()
		y0 = 0
		x1 = p.Width()
		y1 = p.Height()
		orient = OrientVertical
		textAlign = AlignRight
		ticksPaddingLeft = textMaxWidth + tickLength
		labelPaddingRight = width - textMaxWidth
	case PositionRight:
		orient = OrientVertical
		y1 = p.Height()
		labelPaddingLeft = width - textMaxWidth
	default:
		labelPaddingTop = height
		x1 = p.Width()
		orient = OrientHorizontal
	}

	if strokeWidth > 0 {
		p.Child(PainterPaddingOption(Box{
			Top:  ticksPaddingTop,
			Left: ticksPaddingLeft,
		})).Ticks(TicksOption{
			Count:  tickCount,
			Length: tickLength,
			Unit:   unit,
			Orient: orient,
		})
		p.LineStroke([]Point{
			{
				X: x0,
				Y: y0,
			},
			{
				X: x1,
				Y: y1,
			},
		})
	}

	p.Child(PainterPaddingOption(Box{
		Left:  labelPaddingLeft,
		Top:   labelPaddingTop,
		Right: labelPaddingRight,
	})).MultiText(MultiTextOption{
		Align:    textAlign,
		TextList: opt.Data,
		Orient:   orient,
		Unit:     unit,
		Position: labelPosition,
	})
	// 显示辅助线
	if opt.SplitLineShow {
		style.StrokeColor = opt.SplitLineColor
		top.OverrideDrawingStyle(style)
		if isVertical {
			x0 := p.Width()
			x1 := top.Width()
			if opt.Position == PositionRight {
				x0 = 0
				x1 = top.Width() - p.Width()
			}
			for index, y := range autoDivide(height, tickCount) {
				if index == 0 {
					continue
				}
				top.LineStroke([]Point{
					{
						X: x0,
						Y: y,
					},
					{
						X: x1,
						Y: y,
					},
				})
			}
		} else {
			y0 := p.Height() - defaultXAxisHeight
			y1 := top.Height() - defaultXAxisHeight
			for index, x := range autoDivide(width, tickCount) {
				if index == 0 {
					continue
				}
				top.LineStroke([]Point{
					{
						X: x,
						Y: y0,
					},
					{
						X: x,
						Y: y1,
					},
				})
			}
		}
	}

	return Box{
		Bottom: height,
		Right:  width,
	}, nil
}