zntg/ui/label.go

package ui

import (
	"image/color"

	"opslag.de/schobers/geom"
)

type TextOverflow int

const (
	TextOverflowClip TextOverflow = iota
	TextOverflowEllipsis
)

type Label struct {
	ControlBase

	Text         string
	TextOverflow TextOverflow
	DropShadow   color.Color

	desired CachedValue
}

func BuildLabel(text string, fn func(*Label)) *Label {
	var l = &Label{Text: text}
	if fn != nil {
		fn(l)
	}
	return l
}

func (l *Label) hashDesiredSize(ctx Context) string {
	return l.FontName(ctx) + l.Text
}

func (l *Label) desiredSize(ctx Context) interface{} {
	font := l.ActualFont(ctx)
	width := font.WidthOf(l.Text)
	height := font.Height()
	pad := l.ActualTextPadding(ctx)
	return geom.PtF32(pad.Left+width+pad.Right, pad.Top+height+pad.Bottom)
}

func (l *Label) DesiredSize(ctx Context, _ geom.PointF32) geom.PointF32 {
	return l.desired.GetContext(ctx, l.desiredSize, l.hashDesiredSize).(geom.PointF32)
}

func (l *Label) getLabelTopLeft(ctx Context) geom.PointF32 {
	pad := l.ActualTextPadding(ctx)
	bounds := pad.InsetRect(l.bounds)
	switch l.TextAlignment {
	case AlignRight:
		return geom.PtF32(bounds.Max.X, bounds.Min.Y)
	case AlignCenter:
		return geom.PtF32(.5*(bounds.Min.X+bounds.Max.X), bounds.Min.Y)
	default:
		return bounds.Min
	}
}

func (l *Label) Render(ctx Context) {
	l.RenderBackground(ctx)
	fontColor := l.TextColor(ctx)
	font := l.ActualFont(ctx)
	topLeft := l.getLabelTopLeft(ctx)
	text := l.Text
	availableWidth := l.bounds.Dx()
	if l.TextOverflow == TextOverflowEllipsis {
		text = fitTextEllipsis(font, text, availableWidth)
	}
	if l.DropShadow != nil {
		ctx.Renderer().TextAlign(font, topLeft.Add2D(1, 1), l.DropShadow, text, l.TextAlignment)
	}
	ctx.Renderer().TextAlign(font, topLeft, fontColor, text, l.TextAlignment)
}