text/v2: bug fix: StdFace was never released

StdFace was used as a cache key, then these are never released.

This change fixes this issue by adding faceCacheKey and use it as
a cache key.

Updates #498

text/v2/glyph.go

@@ -52,7 +52,7 @@ type glyphImageCacheEntry struct {
 }
 
 type glyphImageCache struct {
-	cache map[Face]map[glyphImageCacheKey]*glyphImageCacheEntry
+	cache map[faceCacheKey]map[glyphImageCacheKey]*glyphImageCacheEntry
 	m     sync.Mutex
 }
 
@@ -62,17 +62,18 @@ func (g *glyphImageCache) getOrCreate(face Face, key glyphImageCacheKey, create
 	g.m.Lock()
 	defer g.m.Unlock()
 
-	e, ok := g.cache[face][key]
+	e, ok := g.cache[face.faceCacheKey()][key]
 	if ok {
 		e.atime = now()
 		return e.image
 	}
 
 	if g.cache == nil {
-		g.cache = map[Face]map[glyphImageCacheKey]*glyphImageCacheEntry{}
+		g.cache = map[faceCacheKey]map[glyphImageCacheKey]*glyphImageCacheEntry{}
 	}
-	if g.cache[face] == nil {
+	faceCacheKey := face.faceCacheKey()
-		g.cache[face] = map[glyphImageCacheKey]*glyphImageCacheEntry{}
+	if g.cache[faceCacheKey] == nil {
+		g.cache[faceCacheKey] = map[glyphImageCacheKey]*glyphImageCacheEntry{}
 	}
 
 	img := create()
@@ -86,7 +87,7 @@ func (g *glyphImageCache) getOrCreate(face Face, key glyphImageCacheKey, create
 		// Keep this until the face is GCed.
 		e.atime = infTime
 	}
-	g.cache[face][key] = e
+	g.cache[faceCacheKey][key] = e
 
 	// Clean up old entries.
 
@@ -95,13 +96,13 @@ func (g *glyphImageCache) getOrCreate(face Face, key glyphImageCacheKey, create
 	// Even after cleaning up the cache, the number of glyphs might still exceed the soft limit, but
 	// this is fine.
 	const cacheSoftLimit = 512
-	if len(g.cache[face]) > cacheSoftLimit {
+	if len(g.cache[faceCacheKey]) > cacheSoftLimit {
-		for key, e := range g.cache[face] {
+		for key, e := range g.cache[faceCacheKey] {
 			// 60 is an arbitrary number.
 			if e.atime >= now()-60 {
 				continue
 			}
-			delete(g.cache[face], key)
+			delete(g.cache[faceCacheKey], key)
 		}
 	}
 
@@ -113,5 +114,5 @@ func (g *glyphImageCache) clear(face Face) {
 
 	g.m.Lock()
 	defer g.m.Unlock()
-	delete(g.cache, face)
+	delete(g.cache, face.faceCacheKey())
 }

text/v2/std.go

@@ -17,6 +17,7 @@ package text
 import (
 	"image"
 	"runtime"
+	"sync/atomic"
 
 	"golang.org/x/image/font"
 	"golang.org/x/image/math/fixed"
@@ -24,6 +25,12 @@ import (
 	"github.com/hajimehoshi/ebiten/v2"
 )
 
+var currentStdFaceID uint64
+
+func nextStdFaceID() uint64 {
+	return atomic.AddUint64(&currentStdFaceID, 1)
+}
+
 var _ Face = (*StdFace)(nil)
 
 // StdFace is a Face implementation for a semi-standard font.Face (golang.org/x/image/font).
@@ -32,6 +39,8 @@ var _ Face = (*StdFace)(nil)
 type StdFace struct {
 	f *faceWithCache
 
+	id uint64
+
 	addr *StdFace
 }
 
@@ -41,6 +50,7 @@ func NewStdFace(face font.Face) *StdFace {
 		f: &faceWithCache{
 			f: face,
 		},
+		id: nextStdFaceID(),
 	}
 	s.addr = s
 	runtime.SetFinalizer(s, theGlyphImageCache.clear)
@@ -71,6 +81,11 @@ func (s *StdFace) UnsafeInternal() any {
 	return s.f.f
 }
 
+// faceCacheKey implements Face.
+func (s *StdFace) faceCacheKey() faceCacheKey {
+	return faceCacheKey(s.id)
+}
+
 // advance implements Face.
 func (s *StdFace) advance(text string) float64 {
 	return fixed26_6ToFloat64(font.MeasureString(s.f, text))

text/v2/text.go

@@ -26,6 +26,8 @@ import (
 	"github.com/hajimehoshi/ebiten/v2"
 )
 
+type faceCacheKey uint64
+
 // Face is an interface representing a font face. The implementations are only GoTextFace and StdFace.
 type Face interface {
 	// Metrics returns the metrics for this Face.
@@ -36,6 +38,8 @@ type Face interface {
 	// This is unsafe since this might make internal cache states out of sync.
 	UnsafeInternal() any
 
+	faceCacheKey() faceCacheKey
+
 	advance(text string) float64
 
 	appendGlyphs(glyphs []Glyph, text string, originX, originY float64) []Glyph