tidbyt · betterengineering · Jul 11, 2022 · Jul 11, 2022 · Jul 11, 2022 · Jul 11, 2022
diff --git a/docs/modules.md b/docs/modules.md
@@ -193,4 +193,49 @@ def main(config):
         print("You win!")
     else:
         print("Better luck next time!")
+```
+
+## Pixlet module: QRCode
+
+The `qrcode` module provides a QR code generator for pixlet!
+
+| Function | Description |
+| --- | --- |
+| `generate(url, size, color?, background?)` | Returns a QR code as an image that can be passed into the image widget. |
+
+Sizing works as follows:
+- `small`: 21x21 pixels
+- `medium`: 25x25 pixels
+- `large`: 29x29 pixels
+
+Note: we're working with some of the smallest possible QR codes in this module, so the amount of data that can be used for the URL is extremely limited.
+
+Example:
+```starlark
+load("cache.star", "cache")
+load("encoding/base64.star", "base64")
+load("render.star", "render")
+load("qrcode.star", "qrcode")
+
+def main(config):
+    url = "https://tidbyt.com?utm_source=pixlet_example"
+
+    data = cache.get(url)
+    if data == None:
+        code = qrcode.generate(
+            url = url,
+            size = "large",
+            color = "#fff",
+            background = "#000",
+        )
+        cache.set(url, base64.encode(code), ttl_seconds = 3600)
+    else:
+        code = base64.decode(data)
+
+    return render.Root(
+        child = render.Padding(
+            child = render.Image(src = code),
+            pad = 1,
+        ),
+    )
 ```
diff --git a/examples/qrcode.star b/examples/qrcode.star
@@ -0,0 +1,26 @@
+load("cache.star", "cache")
+load("encoding/base64.star", "base64")
+load("render.star", "render")
+load("qrcode.star", "qrcode")
+
+def main(config):
+    url = "https://tidbyt.com?utm_source=pixlet_example"
+
+    data = cache.get(url)
+    if data == None:
+        code = qrcode.generate(
+            url = url,
+            size = "large",
+            color = "#fff",
+            background = "#000",
+        )
+        cache.set(url, base64.encode(code), ttl_seconds = 3600)
+    else:
+        code = base64.decode(data)
+
+    return render.Root(
+        child = render.Padding(
+            child = render.Image(src = code),
+            pad = 1,
+        ),
+    )
diff --git a/go.mod b/go.mod
@@ -20,6 +20,7 @@ require (
 	github.com/nfnt/resize v0.0.0-20180221191011-83c6a9932646
 	github.com/pkg/errors v0.9.1
 	github.com/qri-io/starlib v0.5.1-0.20211102160121-ae835e29cd41
+	github.com/skip2/go-qrcode v0.0.0-20200617195104-da1b6568686e // indirect
 	github.com/spf13/cobra v1.5.0
 	github.com/stretchr/testify v1.8.0
 	github.com/tidbyt/go-libwebp v0.0.0-20220302154536-6042ce446e9c

diff --git a/go.sum b/go.sum
@@ -417,6 +417,8 @@ github.com/sergi/go-diff v1.0.0/go.mod h1:0CfEIISq7TuYL3j771MWULgwwjU+GofnZX9QAm
 github.com/shurcooL/sanitized_anchor_name v1.0.0/go.mod h1:1NzhyTcUVG4SuEtjjoZeVRXNmyL/1OwPU0+IJeTBvfc=
 github.com/sirupsen/logrus v1.2.0/go.mod h1:LxeOpSwHxABJmUn/MG1IvRgCAasNZTLOkJPxbbu5VWo=
 github.com/sirupsen/logrus v1.4.2/go.mod h1:tLMulIdttU9McNUspp0xgXVQah82FyeX6MwdIuYE2rE=
+github.com/skip2/go-qrcode v0.0.0-20200617195104-da1b6568686e h1:MRM5ITcdelLK2j1vwZ3Je0FKVCfqOLp5zO6trqMLYs0=
+github.com/skip2/go-qrcode v0.0.0-20200617195104-da1b6568686e/go.mod h1:XV66xRDqSt+GTGFMVlhk3ULuV0y9ZmzeVGR4mloJI3M=
 github.com/soheilhy/cmux v0.1.4/go.mod h1:IM3LyeVVIOuxMH7sFAkER9+bJ4dT7Ms6E4xg4kGIyLM=
 github.com/spaolacci/murmur3 v0.0.0-20180118202830-f09979ecbc72/go.mod h1:JwIasOWyU6f++ZhiEuf87xNszmSA2myDM2Kzu9HwQUA=
 github.com/spf13/afero v1.1.2/go.mod h1:j4pytiNVoe2o6bmDsKpLACNPDBIoEAkihy7loJ1B0CQ=

diff --git a/runtime/applet.go b/runtime/applet.go
@@ -24,6 +24,7 @@ import (
 	"tidbyt.dev/pixlet/render"
 	"tidbyt.dev/pixlet/runtime/modules/animation_runtime"
 	"tidbyt.dev/pixlet/runtime/modules/humanize"
+	"tidbyt.dev/pixlet/runtime/modules/qrcode"
 	"tidbyt.dev/pixlet/runtime/modules/random"
 	"tidbyt.dev/pixlet/runtime/modules/render_runtime"
 	"tidbyt.dev/pixlet/runtime/modules/sunrise"
@@ -347,6 +348,9 @@ func (a *Applet) loadModule(thread *starlark.Thread, module string) (starlark.St
 	case "random.star":
 		return random.LoadModule()
 
+	case "qrcode.star":
+		return qrcode.LoadModule()
+
 	case "assert.star":
 		return starlarktest.LoadAssertModule()
 

diff --git a/runtime/modules/qrcode/qrcode.go b/runtime/modules/qrcode/qrcode.go
@@ -0,0 +1,109 @@
+package qrcode
+
+import (
+	"fmt"
+	"image/color"
+	"sync"
+
+	goqrcode "github.com/skip2/go-qrcode"
+	"go.starlark.net/starlark"
+	"go.starlark.net/starlarkstruct"
+	"tidbyt.dev/pixlet/render"
+)
+
+const (
+	ModuleName = "qrcode"
+)
+
+var (
+	once   sync.Once
+	module starlark.StringDict
+)
+
+func LoadModule() (starlark.StringDict, error) {
+	once.Do(func() {
+		module = starlark.StringDict{
+			ModuleName: &starlarkstruct.Module{
+				Name: ModuleName,
+				Members: starlark.StringDict{
+					"generate": starlark.NewBuiltin("generate", generateQRCode),
+				},
+			},
+		}
+	})
+
+	return module, nil
+}
+
+func generateQRCode(thread *starlark.Thread, _ *starlark.Builtin, args starlark.Tuple, kwargs []starlark.Tuple) (starlark.Value, error) {
+	var (
+		starUrl        starlark.String
+		starSize       starlark.String
+		starColor      starlark.String
+		starBackground starlark.String
+	)
+
+	if err := starlark.UnpackArgs(
+		"generate",
+		args, kwargs,
+		"url", &starUrl,
+		"size", &starSize,
+		"color?", &starColor,
+		"background?", &starBackground,
+	); err != nil {
+		return nil, fmt.Errorf("unpacking arguments for generate: %w", err)
+	}
+
+	// Determine QRCode sizing information.
+	version := 0
+	imgSize := 0
+	switch starSize.GoString() {
+	case "small":
+		version = 1
+		imgSize = 21
+	case "medium":
+		version = 2
+		imgSize = 25
+	case "large":
+		version = 3
+		imgSize = 29
+	default:
+		return nil, fmt.Errorf("size must be small, medium, or large")
+	}
+
+	url := starUrl.String()
+	code, err := goqrcode.NewWithForcedVersion(url, version, goqrcode.Low)
+	if err != nil {
+		return nil, err
+	}
+
+	// Set default styles.
+	code.DisableBorder = true
+	code.ForegroundColor = color.White
+	code.BackgroundColor = color.Transparent
+
+	// Override color if one is provided.
+	if starColor.Len() > 0 {
+		color, err := render.ParseColor(starColor.GoString())
+		if err != nil {
+			return nil, fmt.Errorf("color is not a valid hex string: %s", starColor.String())
+		}
+		code.ForegroundColor = color
+	}
+
+	// Override background if one is provided.
+	if starBackground.Len() > 0 {
+		background, err := render.ParseColor(starBackground.GoString())
+		if err != nil {
+			return nil, fmt.Errorf("color is not a valid hex string: %s", starColor.String())
+		}
+		code.BackgroundColor = background
+	}
+
+	png, err := code.PNG(imgSize)
+	if err != nil {
+		return nil, err
+	}
+
+	return starlark.String(string(png)), nil
+}
diff --git a/runtime/modules/qrcode/qrcode_test.go b/runtime/modules/qrcode/qrcode_test.go
@@ -0,0 +1,38 @@
+package qrcode_test
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"tidbyt.dev/pixlet/runtime"
+)
+
+var qrCodeSource = `
+load("qrcode.star", "qrcode")
+
+def assert(success, message=None):
+    if not success:
+        fail(message or "assertion failed")
+
+
+url = "https://tidbyt.com?utm_source=pixlet_example"
+code = qrcode.generate(
+    url = url,
+    size = "large",
+    color = "#fff",
+    background = "#000",
+)
+
+def main():
+	return []
+`
+
+func TestQRCode(t *testing.T) {
+	app := &runtime.Applet{}
+	err := app.Load("test.star", []byte(qrCodeSource), nil)
+	assert.NoError(t, err)
+
+	screens, err := app.Run(map[string]string{})
+	assert.NoError(t, err)
+	assert.NotNil(t, screens)
+}