adds display package

display/slot.go

@@ -0,0 +1,88 @@
+package display
+
+import (
+	"errors"
+	"fmt"
+	"image/color"
+
+	"git.dvdt.dev/david/bitcoin-ticker-pi/fonts"
+	rgbmatrix "git.dvdt.dev/david/bitcoin-ticker-pi/go-rpi-rgb-led-matrix"
+)
+
+var (
+	ErrUnsupportedSlotHeight = errors.New("unsupported slot height")
+)
+
+type Segment struct {
+	Text   string
+	Color  color.RGBA
+	bitmap [][]color.RGBA
+}
+
+func (s *Segment) Draw(canvas *rgbmatrix.Canvas, x, y int) {
+	for i, row := range s.bitmap {
+		drawRow(canvas, row, x, y+i)
+	}
+}
+
+func drawRow(canvas *rgbmatrix.Canvas, row []color.RGBA, x, y int) {
+	for i := 0; i < len(row); i++ {
+		canvas.Set(x+i, y, row[i])
+	}
+}
+
+type Slot struct {
+	segmentLimit  int
+	segmentHeight int
+	segmentWidth  int
+	x, y          int
+	text          []Segment
+}
+
+func NewSlot(limit, height, width, x, y int) *Slot {
+	return &Slot{
+		segmentLimit:  limit,
+		segmentHeight: height,
+		segmentWidth:  width,
+		x:             x,
+		y:             y,
+		text:          []Segment{},
+	}
+}
+
+func (s *Slot) Update(text []Segment) error {
+	if len(text) > s.segmentLimit {
+		text = text[:s.segmentLimit-3]
+		text = append(text, []Segment{
+			{Text: ".", Color: fonts.White},
+			{Text: ".", Color: fonts.White},
+			{Text: ".", Color: fonts.White},
+		}...)
+	}
+
+	var font fonts.Font
+	switch s.segmentHeight {
+	case 5:
+		font = fonts.Face5x4
+	case 7:
+		font = fonts.Face7x5
+	default:
+		return fmt.Errorf("%w: %d", ErrUnsupportedSlotHeight, s.segmentHeight)
+	}
+
+	for i, t := range text {
+		c, err := font.ToColor(t.Text, t.Color)
+		if err != nil {
+			return err
+		}
+		text[i].bitmap = c
+	}
+	s.text = text
+	return nil
+}
+
+func (s *Slot) Draw(canvas *rgbmatrix.Canvas) {
+	for i, segment := range s.text {
+		segment.Draw(canvas, s.x+(i*s.segmentWidth), s.y)
+	}
+}