From 6a8f37453e1a788c1991f6cdd31299a88b644cd2 Mon Sep 17 00:00:00 2001
From: Hajime Hoshi <hajimehoshi@gmail.com>
Date: Tue, 5 Dec 2023 21:40:53 +0900
Subject: [PATCH] text/v2: bug fix: MultiFace should use the last face as the
 final resort

---
 text/v2/multi.go      |  7 ++---
 text/v2/multi_test.go | 63 +++++++++++++++++++++++++++++++++++++++++++
 text/v2/text_test.go  | 14 ----------
 3 files changed, 67 insertions(+), 17 deletions(-)
 create mode 100644 text/v2/multi_test.go

diff --git a/text/v2/multi.go b/text/v2/multi.go
index 92d517c29..d84ace585 100644
--- a/text/v2/multi.go
+++ b/text/v2/multi.go
@@ -160,17 +160,18 @@ func (m *MultiFace) splitText(text string) []textChunk {
 	var chunks []textChunk
 
 	for ri, r := range text {
-		// -1 indicates the default face index. -1 is used when no face is found for the glyph.
 		fi := -1
-
 		_, l := utf8.DecodeRuneInString(text[ri:])
 		for i, f := range m.faces {
-			if !f.hasGlyph(r) {
+			if !f.hasGlyph(r) && i < len(m.faces)-1 {
 				continue
 			}
 			fi = i
 			break
 		}
+		if fi == -1 {
+			panic("text: a face was not selected correctly")
+		}
 
 		var s int
 		if len(chunks) > 0 {
diff --git a/text/v2/multi_test.go b/text/v2/multi_test.go
new file mode 100644
index 000000000..894447d8b
--- /dev/null
+++ b/text/v2/multi_test.go
@@ -0,0 +1,63 @@
+// Copyright 2023 The Ebitengine Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package text_test
+
+import (
+	"bytes"
+	"testing"
+
+	"github.com/hajimehoshi/bitmapfont/v3"
+	"golang.org/x/image/font/gofont/goregular"
+
+	"github.com/hajimehoshi/ebiten/v2"
+	"github.com/hajimehoshi/ebiten/v2/text/v2"
+)
+
+func TestMultiFace(t *testing.T) {
+	faces := []text.Face{text.NewStdFace(bitmapfont.Face)}
+	f, err := text.NewMultiFace(faces...)
+	if err != nil {
+		t.Fatal(err)
+	}
+	img := ebiten.NewImage(30, 30)
+	text.Draw(img, "Hello", f, nil)
+
+	// Confirm that the given slice doesn't cause crash.
+	faces[0] = nil
+	text.Draw(img, "World", f, nil)
+}
+
+func TestMultiFaceFallback(t *testing.T) {
+	enFaceSource, err := text.NewGoTextFaceSource(bytes.NewReader(goregular.TTF))
+	if err != nil {
+		t.Fatal(err)
+	}
+	enFace := &text.GoTextFace{
+		Source: enFaceSource,
+		Size:   10,
+	}
+	multiFace, err := text.NewMultiFace(enFace)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// If all the faces in a MultiFace doesn't have a glyph, the last face should be used.
+	str := "あ"
+	got := text.AppendGlyphs(nil, str, multiFace, nil)
+	want := text.AppendGlyphs(nil, str, enFace, nil)
+	if len(got) != len(want) {
+		t.Errorf("got: %d, want: %d", len(got), len(want))
+	}
+}
diff --git a/text/v2/text_test.go b/text/v2/text_test.go
index 01e123d62..21b258012 100644
--- a/text/v2/text_test.go
+++ b/text/v2/text_test.go
@@ -240,17 +240,3 @@ func TestUnhashableFace(t *testing.T) {
 		}
 	}
 }
-
-func TestMultiFace(t *testing.T) {
-	faces := []text.Face{text.NewStdFace(bitmapfont.Face)}
-	f, err := text.NewMultiFace(faces...)
-	if err != nil {
-		t.Fatal(err)
-	}
-	img := ebiten.NewImage(30, 30)
-	text.Draw(img, "Hello", f, nil)
-
-	// Confirm that the given slice doesn't cause crash.
-	faces[0] = nil
-	text.Draw(img, "World", f, nil)
-}