mth/ebiten
1
0
Fork 0
mirror of https://github.com/hajimehoshi/ebiten.git synced 2024-11-10 13:07:26 +01:00
Code Issues Packages Projects Releases Wiki Activity

text: Improve the comment

Browse Source
This commit is contained in:
Hajime Hoshi 2021-04-27 01:58:28 +09:00
parent 53e4810b6d
commit ec3e10e3f7
1 changed files with 17 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

19
text/text.go
View File

@ -157,6 +157,13 @@ var textM sync.Mutex
//
// 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.
// The cache is shared with CacheGlyphs.
//
// The two functions are implemented like this:
//
// Draw = Create glyphs by `ReplacePixels` and put them into the cache if necessary
// + Draw them onto the destination by `DrawImage`
// CacheGlyphs = Create glyphs by `ReplacePixels` and put them into the cache if necessary
//
// Be careful that the passed font face is held by this package and is never released.
// This is a known issue (#498).
@ -271,12 +278,20 @@ 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.
// The cache is shared with Draw.
//
// 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
// different operations and can never be merged as one draw call. CacheGlyphs creates necessary glyphs without
// rendering them so that these operations are likely merged into one draw call.
// different operations (ReplacePixels and DrawImage) and can never be merged as 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 `ReplacePixels` and put them into the cache if necessary
// + Draw them onto the destination by `DrawImage`
// CacheGlyphs = Create glyphs by `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) {