Add text rendering for Stream Deck buttons with toggle demo

lib/streamdeck/text.go

@@ -0,0 +1,45 @@
+package streamdeck
+
+import (
+	"image"
+	"image/color"
+	"image/draw"
+	"strings"
+
+	"golang.org/x/image/font"
+	"golang.org/x/image/font/basicfont"
+	"golang.org/x/image/math/fixed"
+)
+
+func TextImage(bg color.Color, fg color.Color, lines ...string) image.Image {
+	img := image.NewRGBA(image.Rect(0, 0, keySize, keySize))
+	draw.Draw(img, img.Bounds(), &image.Uniform{bg}, image.Point{}, draw.Src)
+
+	face := basicfont.Face7x13
+	metrics := face.Metrics()
+	lineHeight := metrics.Height.Ceil()
+
+	totalHeight := lineHeight * len(lines)
+	startY := (keySize-totalHeight)/2 + metrics.Ascent.Ceil()
+
+	for i, line := range lines {
+		width := font.MeasureString(face, line).Ceil()
+		x := (keySize - width) / 2
+		y := startY + i*lineHeight
+
+		d := &font.Drawer{
+			Dst:  img,
+			Src:  &image.Uniform{fg},
+			Face: face,
+			Dot:  fixed.P(x, y),
+		}
+		d.DrawString(line)
+	}
+
+	return img
+}
+
+func (d *Device) SetKeyText(key int, bg color.Color, fg color.Color, text string) error {
+	lines := strings.Split(text, "\n")
+	return d.SetKeyImage(key, TextImage(bg, fg, lines...))
+}