Add initial version of display-command

Signed-off-by: Knut Ahlers <knut@ahlers.me>

cmd/streamdeck/display_command.go

@@ -0,0 +1,165 @@
+package main
+
+import (
+	"bytes"
+	"image"
+	"image/color"
+	"image/draw"
+	_ "image/jpeg"
+	_ "image/png"
+	"io/ioutil"
+	"os"
+	"os/exec"
+	"strings"
+
+	"github.com/golang/freetype"
+	"github.com/golang/freetype/truetype"
+	"github.com/pkg/errors"
+	"golang.org/x/image/font"
+	"golang.org/x/image/math/fixed"
+)
+
+func init() {
+	registerDisplayElement("exec", displayElementCommand{})
+}
+
+type displayElementCommand struct{}
+
+func (d displayElementCommand) Display(idx int, attributes map[string]interface{}) error {
+	var (
+		err error
+		img draw.Image = image.NewRGBA(image.Rect(0, 0, sd.IconSize(), sd.IconSize()))
+	)
+
+	// Initialize black image
+	draw.Draw(img, img.Bounds(), image.NewUniform(color.RGBA{0x0, 0x0, 0x0, 0xff}), image.ZP, draw.Src)
+
+	cmd, ok := attributes["command"].([]interface{})
+	if !ok {
+		return errors.New("No command supplied")
+	}
+
+	var args []string
+	for _, c := range cmd {
+		if v, ok := c.(string); ok {
+			args = append(args, v)
+			continue
+		}
+		return errors.New("Command conatins non-string argument")
+	}
+
+	if filename, ok := attributes["image"].(string); ok {
+		bgi, err := d.getImageFromDisk(filename)
+		if err != nil {
+			return errors.Wrap(err, "Unable to get image from disk")
+		}
+
+		draw.Draw(img, img.Bounds(), bgi, image.ZP, draw.Src)
+	}
+
+	var textColor color.Color = color.RGBA{0xff, 0xff, 0xff, 0xff}
+	if rgba, ok := attributes["color"].([]interface{}); ok {
+		if len(rgba) != 4 {
+			return errors.New("RGBA color definition needs 4 hex values")
+		}
+
+		textColor = color.RGBA{uint8(rgba[0].(int)), uint8(rgba[1].(int)), uint8(rgba[2].(int)), uint8(rgba[3].(int))}
+	}
+
+	var fontsize float64 = 120
+	if v, ok := attributes["font_size"].(float64); ok {
+		fontsize = v
+	}
+
+	var border = 10
+	if v, ok := attributes["border"].(int); ok {
+		border = v
+	}
+
+	var buf = new(bytes.Buffer)
+
+	command := exec.Command(args[0], args[1:]...)
+	command.Env = os.Environ()
+	command.Stdout = buf
+
+	if err := command.Run(); err != nil {
+		return errors.Wrap(err, "Command has exit != 0")
+	}
+
+	f, err := d.loadFont()
+	if err != nil {
+		return errors.Wrap(err, "Unable to load font")
+	}
+
+	c := freetype.NewContext()
+	c.SetClip(img.Bounds())
+	c.SetDPI(72)
+	c.SetDst(img)
+	c.SetFont(f)
+	c.SetHinting(font.HintingNone)
+
+	if strings.TrimSpace(buf.String()) != "" {
+		if err = d.drawText(c, strings.TrimSpace(buf.String()), textColor, fontsize, border); err != nil {
+			return errors.Wrap(err, "Unable to render text")
+		}
+	}
+
+	return errors.Wrap(sd.FillImage(idx, img), "Unable to set image")
+}
+
+func (displayElementCommand) drawText(c *freetype.Context, text string, textColor color.Color, fontsize float64, border int) error {
+	c.SetSrc(image.NewUniform(color.RGBA{0x0, 0x0, 0x0, 0x0})) // Transparent for text size guessing
+
+	var (
+		err error
+		ext fixed.Point26_6
+	)
+	for {
+		c.SetFontSize(fontsize)
+
+		ext, err = c.DrawString(text, freetype.Pt(0, 0))
+		if err != nil {
+			return errors.Wrap(err, "Unable to measure text")
+		}
+
+		if int(float64(ext.X)/64) > sd.IconSize()-2*border || int(c.PointToFixed(fontsize/2.0)/64) > sd.IconSize()-2*border {
+			fontsize -= 2
+			continue
+		}
+
+		break
+	}
+
+	c.SetSrc(image.NewUniform(textColor)) // TODO: Dynamic
+
+	xcenter := (float64(sd.IconSize()-2*border) / 2.0) - (float64(int(float64(ext.X)/64)) / 2.0) + float64(border)
+	ycenter := (float64(sd.IconSize()-2*border) / 2.0) + (float64(c.PointToFixed(fontsize/2.0)/64) / 2.0) + float64(border)
+
+	_, err = c.DrawString(text, freetype.Pt(int(xcenter), int(ycenter)))
+
+	return err
+}
+
+func (displayElementCommand) getImageFromDisk(filename string) (image.Image, error) {
+	f, err := os.Open(filename)
+	if err != nil {
+		return nil, errors.Wrap(err, "Unable to open image")
+	}
+	defer f.Close()
+
+	img, _, err := image.Decode(f)
+	if err != nil {
+		return nil, errors.Wrap(err, "Umable to decode image")
+	}
+
+	return img, nil
+}
+
+func (displayElementCommand) loadFont() (*truetype.Font, error) {
+	fontRaw, err := ioutil.ReadFile(userConfig.RenderFont)
+	if err != nil {
+		return nil, errors.Wrap(err, "Unable to read font file")
+	}
+
+	return truetype.Parse(fontRaw)
+}