ebiten/text/text.go

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// Copyright 2017 The Ebiten 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 offers functions to draw texts on an Ebiten's image.
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//
// Note: This package is experimental and API might be changed.
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package text
import (
"image"
"image/color"
"math"
"golang.org/x/image/font"
"golang.org/x/image/math/fixed"
"github.com/hajimehoshi/ebiten"
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emath "github.com/hajimehoshi/ebiten/internal/math"
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"github.com/hajimehoshi/ebiten/internal/sync"
)
var (
monotonicClock int64
)
func now() int64 {
monotonicClock++
return monotonicClock
}
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var (
charBounds = map[char]fixed.Rectangle26_6{}
)
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type char struct {
face font.Face
rune rune
}
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func (c *char) bounds() fixed.Rectangle26_6 {
if b, ok := charBounds[*c]; ok {
return b
}
b, _, _ := c.face.GlyphBounds(c.rune)
charBounds[*c] = b
return b
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}
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func (c *char) size() fixed.Point26_6 {
b := c.bounds()
return b.Max.Sub(b.Min)
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}
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func (c *char) empty() bool {
s := c.size()
return s.X == 0 || s.Y == 0
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}
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func (c *char) atlasGroup() int {
s := c.size()
w, h := s.X.Ceil(), s.Y.Ceil()
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t := w
if t < h {
t = h
}
// Different images for small runes are inefficient.
// Let's use a same texture atlas for typical character sizes.
if t < 32 {
return 32
}
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return emath.NextPowerOf2Int(t)
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}
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type glyph struct {
char char
index int
atime int64
}
func fixed26_6ToFloat64(x fixed.Int26_6) float64 {
return float64(x) / (1 << 6)
}
func (g *glyph) draw(dst *ebiten.Image, x, y fixed.Int26_6, clr color.Color) {
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cr, cg, cb, ca := clr.RGBA()
if ca == 0 {
return
}
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b := g.char.bounds()
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op := &ebiten.DrawImageOptions{}
op.GeoM.Translate(fixed26_6ToFloat64(x), fixed26_6ToFloat64(y))
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op.GeoM.Translate(fixed26_6ToFloat64(b.Min.X), fixed26_6ToFloat64(b.Min.Y))
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rf := float64(cr) / float64(ca)
gf := float64(cg) / float64(ca)
bf := float64(cb) / float64(ca)
af := float64(ca) / 0xffff
op.ColorM.Scale(rf, gf, bf, af)
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a := atlases[g.char.atlasGroup()]
sx, sy := a.at(g)
r := image.Rect(sx, sy, sx+a.glyphSize, sy+a.glyphSize)
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op.SourceRect = &r
dst.DrawImage(a.image, op)
}
var (
atlases = map[int]*atlas{}
)
type atlas struct {
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// image is the back-end image to hold glyph cache.
image *ebiten.Image
// tmpImage is the temporary image as a renderer source for glyph.
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tmpImage *ebiten.Image
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// glyphSize is the size of one glyph in the cache.
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// This value is always power of 2.
glyphSize int
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charToGlyph map[char]*glyph
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}
func (a *atlas) at(glyph *glyph) (int, int) {
if a.glyphSize != glyph.char.atlasGroup() {
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panic("not reached")
}
w, _ := a.image.Size()
xnum := w / a.glyphSize
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x, y := glyph.index%xnum, glyph.index/xnum
return x * a.glyphSize, y * a.glyphSize
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}
func (a *atlas) maxGlyphNum() int {
w, h := a.image.Size()
xnum := w / a.glyphSize
ynum := h / a.glyphSize
return xnum * ynum
}
func (a *atlas) appendGlyph(face font.Face, rune rune, now int64) *glyph {
g := &glyph{
char: char{face, rune},
atime: now,
}
if len(a.charToGlyph) == a.maxGlyphNum() {
var oldest *glyph
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t := int64(math.MaxInt64)
for _, g := range a.charToGlyph {
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if g.atime < t {
t = g.atime
oldest = g
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}
}
if oldest == nil {
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panic("not reached")
}
idx := oldest.index
delete(a.charToGlyph, oldest.char)
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g.index = idx
} else {
g.index = len(a.charToGlyph)
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}
a.charToGlyph[g.char] = g
a.draw(g)
return g
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}
func (a *atlas) draw(glyph *glyph) {
if a.tmpImage == nil {
a.tmpImage, _ = ebiten.NewImage(a.glyphSize, a.glyphSize, ebiten.FilterNearest)
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}
dst := image.NewRGBA(image.Rect(0, 0, a.glyphSize, a.glyphSize))
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d := font.Drawer{
Dst: dst,
Src: image.White,
Face: glyph.char.face,
}
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b := glyph.char.bounds()
d.Dot = fixed.Point26_6{-b.Min.X, -b.Min.Y}
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d.DrawString(string(glyph.char.rune))
a.tmpImage.ReplacePixels(dst.Pix)
op := &ebiten.DrawImageOptions{}
x, y := a.at(glyph)
op.GeoM.Translate(float64(x), float64(y))
op.CompositeMode = ebiten.CompositeModeCopy
a.image.DrawImage(a.tmpImage, op)
a.tmpImage.Clear()
}
func getGlyphFromCache(face font.Face, r rune, now int64) *glyph {
ch := char{face, r}
a, ok := atlases[ch.atlasGroup()]
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if ok {
g, ok := a.charToGlyph[ch]
if ok {
g.atime = now
return g
}
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}
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if ch.empty() {
// The glyph doesn't have its size but might have valid 'advance' parameter
// when ch is e.g. space (U+0020).
return &glyph{
char: ch,
atime: now,
}
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}
if !ok {
// Don't use ebiten.MaxImageSize here.
// It's because the back-end image pixels will be restored from GPU
// whenever a new glyph is rendered on the image, and restoring cost is
// expensive if the image is big.
// The back-end image is updated a temporary image, and the temporary image is
// always cleared after used. This means that there is no clue to restore
// the back-end image without reading from GPU
// (see the package 'restorable' implementation).
//
// TODO: How about making a new function for 'flagile' image?
const size = 1024
i, _ := ebiten.NewImage(size, size, ebiten.FilterNearest)
a = &atlas{
image: i,
glyphSize: ch.atlasGroup(),
charToGlyph: map[char]*glyph{},
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}
atlases[ch.atlasGroup()] = a
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}
return a.appendGlyph(ch.face, ch.rune, now)
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}
var textM sync.Mutex
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// Draw draws a given text on a given destination image dst.
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//
// face is the font for text rendering.
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// (x, y) represents a 'dot' (period) position.
// Be careful that this doesn't represent left-upper corner position.
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// clr is the color for text rendering.
//
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// Glyphs used for rendering are cached in least-recently-used way.
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// It is OK to call this function with a same text and a same face at every frame in terms of performance.
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//
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// This function is concurrent-safe.
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func Draw(dst *ebiten.Image, text string, face font.Face, x, y int, clr color.Color) {
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textM.Lock()
n := now()
fx := fixed.I(x)
prevC := rune(-1)
runes := []rune(text)
for _, c := range runes {
if prevC >= 0 {
fx += face.Kern(prevC, c)
}
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if g := getGlyphFromCache(face, c, n); g != nil {
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if !g.char.empty() {
g.draw(dst, fx, fixed.I(y), clr)
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}
a, _ := face.GlyphAdvance(c)
fx += a
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}
prevC = c
}
textM.Unlock()
}