fix: fallback to username if chars in name are not supported for avatars

backend/internal/utils/image/profile_picture.go

@@ -7,6 +7,8 @@ import (
 	"image"
 	"image/color"
 	"io"
+	"strings"
+	"sync"
 
 	"github.com/boxes-ltd/imaging"
 	"github.com/disintegration/imageorient"
@@ -15,6 +17,7 @@ import (
 	"golang.org/x/image/math/fixed"
 	"golang.org/x/image/webp"
 
+	"github.com/pocket-id/pocket-id/backend/internal/utils"
 	"github.com/pocket-id/pocket-id/backend/resources"
 )
 
@@ -84,21 +87,58 @@ func centerSquare(img image.Image) image.Image {
 	return sub.SubImage(image.Rect(x, y, x+side, y+side))
 }
 
+var loadInitialsFont = sync.OnceValues(func() (*opentype.Font, error) {
+	fontBytes, err := resources.FS.ReadFile("fonts/Gloock.ttf")
+	if err != nil {
+		return nil, fmt.Errorf("failed to read font file: %w", err)
+	}
+
+	fontFace, err := opentype.Parse(fontBytes)
+	if err != nil {
+		return nil, fmt.Errorf("failed to parse font: %w", err)
+	}
+
+	return fontFace, nil
+})
+
+// Initials returns the initials shown on the default profile picture
+func Initials(firstName, lastName, username string) string {
+	// The font only covers Latin, so names it can't render fall back to the username, which is always ASCII
+	initials := strings.ToUpper(utils.GetFirstCharacter(firstName) + utils.GetFirstCharacter(lastName))
+	if initials != "" && canRenderInitials(initials) {
+		return initials
+	}
+
+	return strings.ToUpper(utils.GetFirstCharacter(username))
+}
+
+// canRenderInitials reports whether the initials font has a glyph for every character of the initials
+// The font only covers Latin, so other scripts would otherwise be drawn as empty boxes
+func canRenderInitials(initials string) bool {
+	fontFace, err := loadInitialsFont()
+	if err != nil {
+		return false
+	}
+
+	for _, r := range initials {
+		idx, err := fontFace.GlyphIndex(nil, r)
+		if err != nil || idx == 0 {
+			return false
+		}
+	}
+
+	return true
+}
+
 // CreateDefaultProfilePicture creates a profile picture with the initials
 func CreateDefaultProfilePicture(initials string) (*bytes.Buffer, error) {
 	// Create a blank image with a white background
 	img := imaging.New(profilePictureSize, profilePictureSize, color.RGBA{R: 255, G: 255, B: 255, A: 255})
 
 	// Load the font
-	fontBytes, err := resources.FS.ReadFile("fonts/Gloock.ttf")
+	fontFace, err := loadInitialsFont()
 	if err != nil {
-		return nil, fmt.Errorf("failed to read font file: %w", err)
-	}
-
-	// Parse the font
-	fontFace, err := opentype.Parse(fontBytes)
-	if err != nil {
-		return nil, fmt.Errorf("failed to parse font: %w", err)
+		return nil, err
 	}
 
 	// Create a font.Face with a specific size

backend/internal/utils/image/profile_picture_test.go

@@ -0,0 +1,41 @@
+package profilepicture
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestInitials(t *testing.T) {
+	tests := []struct {
+		name      string
+		firstName string
+		lastName  string
+		username  string
+		expected  string
+	}{
+		{name: "first and last name", firstName: "John", lastName: "Doe", username: "username", expected: "JD"},
+		{name: "first name only", firstName: "John", username: "username", expected: "J"},
+		{name: "last name only", lastName: "Doe", username: "username", expected: "D"},
+		{name: "accented Latin name", firstName: "émile", lastName: "Öz", username: "username", expected: "ÉÖ"},
+		{name: "name the font can't render falls back to username", firstName: "민준", lastName: "김", username: "kim", expected: "K"},
+		{name: "partially unrenderable name falls back to username", firstName: "John", lastName: "Иванов", username: "ivan", expected: "I"},
+		{name: "ASCII username", username: "username", expected: "U"},
+		{name: "single-character username", username: "a", expected: "A"},
+		{name: "empty username", expected: ""},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			assert.Equal(t, tt.expected, Initials(tt.firstName, tt.lastName, tt.username))
+		})
+	}
+}
+
+func TestCanRenderInitials(t *testing.T) {
+	assert.True(t, canRenderInitials("ES"))
+	assert.True(t, canRenderInitials("ÉÖ"))
+	assert.True(t, canRenderInitials("0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"))
+	assert.False(t, canRenderInitials("한글"))
+	assert.False(t, canRenderInitials("EЖ"))
+}