From 202fa5e6e7495b95d1a00759583a48aeff9a7540 Mon Sep 17 00:00:00 2001 From: Hajime Hoshi Date: Tue, 27 Apr 2021 02:28:52 +0900 Subject: [PATCH] text: Improve the comment --- text/text.go | 23 +++++++++++++++-------- 1 file changed, 15 insertions(+), 8 deletions(-) diff --git a/text/text.go b/text/text.go index 1e9a43d6f..f544280ec 100644 --- a/text/text.go +++ b/text/text.go @@ -156,10 +156,13 @@ var textM sync.Mutex // Line height is based on Metrics().Height of the font. // // Glyphs used for rendering are cached in least-recently-used way. -// It is OK to call Draw with a same text and a same face at every frame in terms of performance. +// Then old glyphs might be evicted from the cache. +// It is not guaranteed that all the glyphs given at Draw are cached. // The cache is shared with CacheGlyphs. // -// The two functions are implemented like this: +// It is OK to call Draw with a same text and a same face at every frame in terms of performance. +// +// Draw and CacheGlyphs are implemented like this: // // Draw = Create glyphs by `(*ebiten.Image).ReplacePixels` and put them into the cache if necessary // + Draw them onto the destination by `(*ebiten.Image).DrawImage` @@ -278,8 +281,18 @@ func BoundString(face font.Face, text string) image.Rectangle { } // CacheGlyphs precaches the glyphs for the given text and the given font face into the cache. +// +// Glyphs used for rendering are cached in least-recently-used way. +// Then old glyphs might be evicted from the cache. +// It is not guaranteed that all the glyphs given at CacheGlyphs are cached. // The cache is shared with Draw. // +// Draw and CacheGlyphs are implemented like this: +// +// Draw = Create glyphs by `(*ebiten.Image).ReplacePixels` and put them into the cache if necessary +// + Draw them onto the destination by `(*ebiten.Image).DrawImage` +// CacheGlyphs = Create glyphs by `(*ebiten.Image).ReplacePixels` and put them into the cache if necessary +// // Draw automatically creates and caches necessary glyphs, so usually you don't have to call CacheGlyphs // explicitly. However, for example, when you call Draw for each rune of one big text, Draw tries to create the glyph // cache and render it for each rune. This is very inefficient because creating a glyph image and rendering it are @@ -287,12 +300,6 @@ func BoundString(face font.Face, text string) image.Rectangle { // one draw call. CacheGlyphs creates necessary glyphs without rendering them so that these operations are likely // merged into one draw call regardless of the size of the text. // -// The two functions are implemented like this: -// -// Draw = Create glyphs by `(*ebiten.Image).ReplacePixels` and put them into the cache if necessary -// + Draw them onto the destination by `(*ebiten.Image).DrawImage` -// CacheGlyphs = Create glyphs by `(*ebiten.Image).ReplacePixels` and put them into the cache if necessary -// // If a rune's glyph is already cached, CacheGlyphs does nothing for the rune. func CacheGlyphs(face font.Face, text string) { textM.Lock()