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text: Improve the comment
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parent
df4c8532df
commit
202fa5e6e7
23
text/text.go
23
text/text.go
@ -156,10 +156,13 @@ var textM sync.Mutex
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// Line height is based on Metrics().Height of the font.
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//
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// Glyphs used for rendering are cached in least-recently-used way.
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// It is OK to call Draw with a same text and a same face at every frame in terms of performance.
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// Then old glyphs might be evicted from the cache.
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// It is not guaranteed that all the glyphs given at Draw are cached.
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// The cache is shared with CacheGlyphs.
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//
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// The two functions are implemented like this:
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// It is OK to call Draw with a same text and a same face at every frame in terms of performance.
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//
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// Draw and CacheGlyphs are implemented like this:
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//
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// Draw = Create glyphs by `(*ebiten.Image).ReplacePixels` and put them into the cache if necessary
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// + Draw them onto the destination by `(*ebiten.Image).DrawImage`
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@ -278,8 +281,18 @@ func BoundString(face font.Face, text string) image.Rectangle {
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}
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// CacheGlyphs precaches the glyphs for the given text and the given font face into the cache.
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//
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// Glyphs used for rendering are cached in least-recently-used way.
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// Then old glyphs might be evicted from the cache.
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// It is not guaranteed that all the glyphs given at CacheGlyphs are cached.
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// The cache is shared with Draw.
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//
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// Draw and CacheGlyphs are implemented like this:
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//
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// Draw = Create glyphs by `(*ebiten.Image).ReplacePixels` and put them into the cache if necessary
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// + Draw them onto the destination by `(*ebiten.Image).DrawImage`
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// CacheGlyphs = Create glyphs by `(*ebiten.Image).ReplacePixels` and put them into the cache if necessary
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//
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// Draw automatically creates and caches necessary glyphs, so usually you don't have to call CacheGlyphs
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// explicitly. However, for example, when you call Draw for each rune of one big text, Draw tries to create the glyph
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// cache and render it for each rune. This is very inefficient because creating a glyph image and rendering it are
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@ -287,12 +300,6 @@ func BoundString(face font.Face, text string) image.Rectangle {
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// one draw call. CacheGlyphs creates necessary glyphs without rendering them so that these operations are likely
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// merged into one draw call regardless of the size of the text.
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//
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// The two functions are implemented like this:
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//
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// Draw = Create glyphs by `(*ebiten.Image).ReplacePixels` and put them into the cache if necessary
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// + Draw them onto the destination by `(*ebiten.Image).DrawImage`
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// CacheGlyphs = Create glyphs by `(*ebiten.Image).ReplacePixels` and put them into the cache if necessary
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//
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// If a rune's glyph is already cached, CacheGlyphs does nothing for the rune.
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func CacheGlyphs(face font.Face, text string) {
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textM.Lock()
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