Add support for dark mode icons on macos

cmd/fyne/internal/commands/data.go

@@ -4,6 +4,7 @@ import "fyne.io/tools/cmd/fyne/internal/metadata"
 
 type appData struct {
 	icon, Name        string
+	darkIcon          string
 	AppID, AppVersion string
 	AppBuild          int
 	ResGoString       string
@@ -33,6 +34,9 @@ func (a *appData) mergeMetadata(data *metadata.FyneApp) {
 	if a.icon == "" {
 		a.icon = data.Details.Icon
 	}
+	if a.darkIcon == "" {
+		a.darkIcon = data.Details.DarkIcon
+	}
 	if a.Name == "" {
 		a.Name = data.Details.Name
 	}

cmd/fyne/internal/commands/flags.go

@@ -70,6 +70,13 @@ var stringFlags = map[string]func(*string) cli.Flag{
 			Destination: dst,
 		}
 	},
+	"dark-icon": func(dst *string) cli.Flag {
+		return &cli.StringFlag{
+			Name:        "dark-icon",
+			Usage:       "set name of the application icon file in dark mode (where supported)",
+			Destination: dst,
+		}
+	},
 	"developer": func(dst *string) cli.Flag {
 		return &cli.StringFlag{
 			Name:        "developer",

cmd/fyne/internal/commands/package-darwin.go

@@ -1,9 +1,12 @@
 package commands
 
 import (
+	"bytes"
+	"encoding/binary"
 	"fmt"
 	"image"
 	"image/color"
+	"io"
 	"os"
 	"path/filepath"
 	"strings"
@@ -24,6 +27,12 @@ type darwinData struct {
 	Languages     []string
 }
 
+const (
+	icnsHeaderSize = 8
+	icnsMagicSize  = 4
+	icnsOSTypeDark = "\xFD\xD9\x2F\xA8"
+)
+
 func darwinLangs(langs []string) []string {
 	r := make([]string, len(langs))
 	for n, lang := range langs {
@@ -65,14 +74,29 @@ func (p *Packager) packageDarwin() (err error) {
 	resDir := util.EnsureSubDir(contentsDir, "Resources")
 	icnsPath := filepath.Join(resDir, "icon.icns")
 
-	img, err := os.Open(p.icon)
+	srcImg, err := loadIcon(p.icon)
 	if err != nil {
-		return fmt.Errorf("failed to open source image \"%s\": %w", p.icon, err)
+		return err
 	}
-	defer img.Close()
-	srcImg, _, err := image.Decode(img)
-	if err != nil {
-		return fmt.Errorf("failed to decode source image: %w", err)
+	if !p.rawIcon {
+		srcImg = processMacOSIcon(srcImg)
+	}
+	buf := &bytes.Buffer{}
+	if err := icns.Encode(buf, srcImg); err != nil {
+		return fmt.Errorf("failed to encode icns: %w", err)
+	}
+
+	if p.darkIcon != "" {
+		darkSrcImg, err := loadIcon(p.darkIcon)
+		if err != nil {
+			return err
+		}
+		if !p.rawIcon {
+			darkSrcImg = processMacOSIcon(darkSrcImg)
+		}
+		if err := injectDarkIcon(darkSrcImg, buf); err != nil {
+			return err
+		}
 	}
 	dest, err := os.Create(icnsPath)
 	if err != nil {
@@ -83,16 +107,28 @@ func (p *Packager) packageDarwin() (err error) {
 			err = r
 		}
 	}()
-	if !p.rawIcon {
-		srcImg = processMacOSIcon(srcImg)
-	}
-	if err := icns.Encode(dest, srcImg); err != nil {
-		return fmt.Errorf("failed to encode icns: %w", err)
+	if _, err := io.Copy(dest, buf); err != nil {
+		return fmt.Errorf("failed to write destination file: %w", err)
 	}
 
 	return nil
 }
 
+func loadIcon(icon string) (image.Image, error) {
+	f, err := os.Open(icon)
+	if err != nil {
+		return nil, fmt.Errorf("failed to open source image %q: %w", icon, err)
+	}
+	defer f.Close()
+
+	img, _, err := image.Decode(f)
+	if err != nil {
+		return nil, fmt.Errorf("failed to decode source image: %w", err)
+	}
+
+	return img, nil
+}
+
 func processMacOSIcon(in image.Image) image.Image {
 	size := 1024
 	border := 100
@@ -113,3 +149,24 @@ func processMacOSIcon(in image.Image) image.Image {
 
 	return dc.Image()
 }
+
+func injectDarkIcon(darkImg image.Image, buf *bytes.Buffer) error {
+	buf2 := &bytes.Buffer{}
+	if err := icns.Encode(buf2, darkImg); err != nil {
+		return fmt.Errorf("failed to encode icns: %w", err)
+	}
+
+	if _, err := buf.WriteString(icnsOSTypeDark); err != nil {
+		return fmt.Errorf("failed to append dark icon header: %w", err)
+	}
+	if err := binary.Write(buf, binary.BigEndian, uint32(buf2.Len()-icnsHeaderSize)); err != nil {
+		return fmt.Errorf("failed to append dark icon length: %w", err)
+	}
+	if _, err := buf.Write(buf2.Bytes()[icnsHeaderSize:]); err != nil {
+		return fmt.Errorf("failed to append dark icon data: %w", err)
+	}
+
+	binary.BigEndian.PutUint32(buf.Bytes()[icnsMagicSize:], uint32(buf.Len()))
+
+	return nil
+}

cmd/fyne/internal/commands/package.go

@@ -48,6 +48,7 @@ func Package() *cli.Command {
 			intFlags["app-build"](&p.AppBuild),
 			stringFlags["src"](&p.srcDir),
 			stringFlags["icon"](&p.icon),
+			stringFlags["dark-icon"](&p.darkIcon),
 			boolFlags["use-raw-icon"](&p.rawIcon),
 			stringFlags["app-id"](&p.AppID),
 			stringFlags["certificate"](&p.certificate),

cmd/fyne/internal/metadata/data.go

@@ -17,6 +17,7 @@ type FyneApp struct {
 // AppDetails describes the build information, this group may be OS or arch specific
 type AppDetails struct {
 	Icon     string `toml:",omitempty"`
+	DarkIcon string `toml:",omitempty"`
 	Name, ID string `toml:",omitempty"`
 	Version  string `toml:",omitempty"`
 	Build    int    `toml:",omitempty"`