ui/screen/canvas.go

package screen

import (
	"errors"
	"fmt"
	"image/color"

	"fyne.io/fyne/v2"
	"fyne.io/fyne/v2/canvas"
	"fyne.io/fyne/v2/data/binding"
)

type Canvas string

const (
	Image     Canvas = "Image"
	Rectangle Canvas = "Rectangle"
	Text      Canvas = "Text"
)

func (c Canvas) Build(
	e *Element,
	s ScreenHandler,
) (
	cnv fyne.CanvasObject,
	decorator fyne.CanvasObject,
	err error,
) {
	e.localize(s)

	switch c {
	case Image:
		cnv, err = c.BuildImageCanvas(e, s)
	case Rectangle:
		cnv, err = c.BuildRectangleCanvas(e, s)
	case Text:
		cnv, err = c.BuildTextCanvas(e, s)
	default:
		err = errors.New("invalid canvas")
	}

	if err != nil {
		return
	}

	decorator = applyPadding(e, cnv)
	decorator = applyDecorators(e, decorator)
	decorator = applyMargins(e, decorator)

	if e.Hidden {
		decorator.Hide()
	}
	return
}

func (c *Canvas) BuildImageCanvas(
	e *Element,
	s ScreenHandler,
) (obj fyne.CanvasObject, err error) {
	var img *canvas.Image

	if e.ImageName != "" {
		img, err = AssetToImage(s, e.ImageName)
		if err != nil {
			err = fmt.Errorf("failed to load image: %w", err)
			return
		}
	} else {
		img = &canvas.Image{}
	}
	if e.Translucency != nil {
		img.Translucency = *e.Translucency
	}

	for opt, val := range e.Options {
		switch opt {
		case "scaleMode":
			img.ScaleMode = getImageScale(val)
		case "fillMode":
			img.FillMode = getImageFill(val)
		}
	}

	obj = img

	return
}

func (c Canvas) BuildRectangleCanvas(
	e *Element,
	s ScreenHandler,
) (obj fyne.CanvasObject, err error) {
	fClr := color.RGBA{R: 255, G: 255, B: 255, A: 255}
	if e.FillColor != nil {
		fClr = color.RGBA{
			R: e.FillColor.Red,
			G: e.FillColor.Green,
			B: e.FillColor.Blue,
			A: e.FillColor.Alpha,
		}
	}
	rect := canvas.NewRectangle(fClr)
	if e.StrokeColor != nil {
		rect.StrokeColor = color.RGBA{
			R: e.StrokeColor.Red,
			G: e.StrokeColor.Green,
			B: e.StrokeColor.Blue,
			A: e.StrokeColor.Alpha,
		}
	}
	rect.StrokeWidth = 0
	rect.CornerRadius = 0
	if e.StrokeWidth != nil {
		rect.StrokeWidth = *e.StrokeWidth
	}
	if e.CornerRadius != nil {
		rect.CornerRadius = *e.CornerRadius
	}
	obj = rect
	return
}

func (c Canvas) BuildTextCanvas(
	e *Element,
	s ScreenHandler,
) (obj fyne.CanvasObject, err error) {
	txtClr := color.RGBA{R: 255, G: 255, B: 255, A: 255}
	if e.TextColor != nil {
		txtClr = color.RGBA{
			R: e.TextColor.Red,
			G: e.TextColor.Green,
			B: e.TextColor.Blue,
			A: e.TextColor.Alpha,
		}
	}

	txt := canvas.NewText(e.Text, txtClr)
	if e.Binding != "" {
		bnd := s.GetBinding(e.Binding).(binding.String)
		bnd.AddListener(binding.NewDataListener(func() {
			txt.Text, _ = bnd.Get()
			txt.Refresh()
		}))
	}

	if e.TextSize != nil {
		txt.TextSize = *e.TextSize
	}

	for opt, val := range e.Options {
		switch opt {
		case "alignment":
			txt.Alignment = getTextAlignment(val)
		case "textStyle":
			txt.TextStyle = getTextStyle(val)
		}
	}
	obj = txt
	return
}

func getImageFill(v any) canvas.ImageFill {
	switch v.(string) {
	case "Stretch":
		return canvas.ImageFillStretch
	case "Contain":
		return canvas.ImageFillContain
	case "Original":
		return canvas.ImageFillOriginal
	}
	return canvas.ImageFillStretch
}

func getImageScale(v any) canvas.ImageScale {
	switch v.(string) {
	case "Smooth":
		return canvas.ImageScaleSmooth
	case "Pixels":
		return canvas.ImageScalePixels
	case "Fastest":
		return canvas.ImageScaleFastest
	}
	return canvas.ImageScaleSmooth
}