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glyph.go
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glyph.go
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// 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
import (
"math"
"sync"
"github.com/hajimehoshi/ebiten/v2"
"github.com/hajimehoshi/ebiten/v2/internal/hook"
)
var monotonicClock int64
const infTime = math.MaxInt64
func now() int64 {
return monotonicClock
}
func init() {
hook.AppendHookOnBeforeUpdate(func() error {
monotonicClock++
return nil
})
}
type glyphImageCacheEntry struct {
image *ebiten.Image
atime int64
}
type glyphImageCache[Key comparable] struct {
cache map[Key]*glyphImageCacheEntry
m sync.Mutex
}
func (g *glyphImageCache[Key]) getOrCreate(face Face, key Key, create func() *ebiten.Image) *ebiten.Image {
g.m.Lock()
defer g.m.Unlock()
e, ok := g.cache[key]
if ok {
e.atime = now()
return e.image
}
if g.cache == nil {
g.cache = map[Key]*glyphImageCacheEntry{}
}
img := create()
e = &glyphImageCacheEntry{
image: img,
}
if img != nil {
e.atime = now()
} else {
// If the glyph image is nil, the entry doesn't have to be removed.
// Keep this until the face is GCed.
e.atime = infTime
}
g.cache[key] = e
// Clean up old entries.
// cacheSoftLimit indicates the soft limit of the number of glyphs in the cache.
// If the number of glyphs exceeds this soft limits, old glyphs are removed.
// Even after cleaning up the cache, the number of glyphs might still exceed the soft limit, but
// this is fine.
cacheSoftLimit := 128 * glyphVariationCount(face)
if len(g.cache) > cacheSoftLimit {
for key, e := range g.cache {
// 60 is an arbitrary number.
if e.atime >= now()-60 {
continue
}
delete(g.cache, key)
}
}
return img
}