PoC: text/v2 glyph atlas

text/v2/atlas.go

@@ -0,0 +1,297 @@
+// Copyright 2024 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 (
+	"github.com/hajimehoshi/ebiten/v2"
+	"github.com/hajimehoshi/ebiten/v2/internal/packing"
+)
+
+type glyphAtlas struct {
+	page  *packing.Page
+	image *ebiten.Image
+}
+
+type glyphImage struct {
+	atlas *glyphAtlas
+	node  *packing.Node
+	img   *ebiten.Image
+}
+
+func (i *glyphImage) Image() *ebiten.Image {
+	return i.img
+}
+
+func newGlyphAtlas() *glyphAtlas {
+	return &glyphAtlas{
+		// Note: 128x128 is arbitrary, maybe a better value can be inferred
+		// from the font size or something
+		page:  packing.NewPage(128, 128, 1024), // TODO: not 1024
+		image: ebiten.NewImage(128, 128),
+	}
+}
+
+func (g *glyphAtlas) NewImage(w, h int) *glyphImage {
+	n := g.page.Alloc(w, h)
+	pw, ph := g.page.Size()
+	if pw > g.image.Bounds().Dx() || ph > g.image.Bounds().Dy() {
+		newImage := ebiten.NewImage(pw, ph)
+		newImage.DrawImage(g.image, nil)
+		g.image = newImage
+	}
+
+	return &glyphImage{
+		atlas: g,
+		node:  n,
+		img:   g.image.SubImage(n.Region()).(*ebiten.Image),
+	}
+}
+
+func (g *glyphAtlas) Free(img *glyphImage) {
+	g.page.Free(img.node)
+}
+
+type drawRange struct {
+	atlas *glyphAtlas
+	end   int
+}
+
+// drawList stores triangle versions of DrawImage calls when
+// all images are sub-images of an atlas.
+// Temporary vertices and indices can be re-used after calling
+// Flush, so it is more efficient to keep a reference to a drawList
+// instead of creating a new one every frame.
+type drawList struct {
+	ranges []drawRange
+	vx     []ebiten.Vertex
+	ix     []uint16
+}
+
+// drawCommand is the equivalent of the regular DrawImageOptions
+// but only including options that will not break batching.
+// Filter, Address, Blend and AntiAlias are determined at Flush()
+type drawCommand struct {
+	Image *glyphImage
+
+	ColorScale ebiten.ColorScale
+	GeoM       ebiten.GeoM
+}
+
+var rectIndices = [6]uint16{0, 1, 2, 1, 2, 3}
+
+type point struct {
+	X, Y float32
+}
+
+func pt(x, y float64) point {
+	return point{
+		X: float32(x),
+		Y: float32(y),
+	}
+}
+
+type rectOpts struct {
+	Dsts         [4]point
+	SrcX0, SrcY0 float32
+	SrcX1, SrcY1 float32
+	R, G, B, A   float32
+}
+
+// adjustDestinationPixel is the original ebitengine implementation found here:
+// https://github.com/hajimehoshi/ebiten/blob/v2.8.0-alpha.1/internal/graphics/vertex.go#L102-L126
+func adjustDestinationPixel(x float32) float32 {
+	// Avoid the center of the pixel, which is problematic (#929, #1171).
+	// Instead, align the vertices with about 1/3 pixels.
+	//
+	// The intention here is roughly this code:
+	//
+	//     float32(math.Floor((float64(x)+1.0/6.0)*3) / 3)
+	//
+	// The actual implementation is more optimized than the above implementation.
+	ix := float32(int(x))
+	if x < 0 && x != ix {
+		ix -= 1
+	}
+	frac := x - ix
+	switch {
+	case frac < 3.0/16.0:
+		return ix
+	case frac < 8.0/16.0:
+		return ix + 5.0/16.0
+	case frac < 13.0/16.0:
+		return ix + 11.0/16.0
+	default:
+		return ix + 16.0/16.0
+	}
+}
+
+func appendRectVerticesIndices(vertices []ebiten.Vertex, indices []uint16, index int, opts *rectOpts) ([]ebiten.Vertex, []uint16) {
+	sx0, sy0, sx1, sy1 := opts.SrcX0, opts.SrcY0, opts.SrcX1, opts.SrcY1
+	r, g, b, a := opts.R, opts.G, opts.B, opts.A
+	vertices = append(vertices,
+		ebiten.Vertex{
+			DstX:   adjustDestinationPixel(opts.Dsts[0].X),
+			DstY:   adjustDestinationPixel(opts.Dsts[0].Y),
+			SrcX:   sx0,
+			SrcY:   sy0,
+			ColorR: r,
+			ColorG: g,
+			ColorB: b,
+			ColorA: a,
+		},
+		ebiten.Vertex{
+			DstX:   adjustDestinationPixel(opts.Dsts[1].X),
+			DstY:   adjustDestinationPixel(opts.Dsts[1].Y),
+			SrcX:   sx1,
+			SrcY:   sy0,
+			ColorR: r,
+			ColorG: g,
+			ColorB: b,
+			ColorA: a,
+		},
+		ebiten.Vertex{
+			DstX:   adjustDestinationPixel(opts.Dsts[2].X),
+			DstY:   adjustDestinationPixel(opts.Dsts[2].Y),
+			SrcX:   sx0,
+			SrcY:   sy1,
+			ColorR: r,
+			ColorG: g,
+			ColorB: b,
+			ColorA: a,
+		},
+		ebiten.Vertex{
+			DstX:   adjustDestinationPixel(opts.Dsts[3].X),
+			DstY:   adjustDestinationPixel(opts.Dsts[3].Y),
+			SrcX:   sx1,
+			SrcY:   sy1,
+			ColorR: r,
+			ColorG: g,
+			ColorB: b,
+			ColorA: a,
+		},
+	)
+
+	indiceCursor := uint16(index * 4)
+	indices = append(indices,
+		rectIndices[0]+indiceCursor,
+		rectIndices[1]+indiceCursor,
+		rectIndices[2]+indiceCursor,
+		rectIndices[3]+indiceCursor,
+		rectIndices[4]+indiceCursor,
+		rectIndices[5]+indiceCursor,
+	)
+
+	return vertices, indices
+}
+
+// Add adds DrawImage commands to the DrawList, images from multiple
+// atlases can be added but they will break the previous batch bound to
+// a different atlas, requiring an additional draw call internally.
+// So, it is better to have the maximum of consecutive DrawCommand images
+// sharing the same atlas.
+func (dl *drawList) Add(commands ...*drawCommand) {
+	if len(commands) == 0 {
+		return
+	}
+
+	var batch *drawRange
+
+	if len(dl.ranges) > 0 {
+		batch = &dl.ranges[len(dl.ranges)-1]
+	} else {
+		dl.ranges = append(dl.ranges, drawRange{
+			atlas: commands[0].Image.atlas,
+		})
+		batch = &dl.ranges[0]
+	}
+	// Add vertices and indices
+	opts := &rectOpts{}
+	for _, cmd := range commands {
+		if cmd.Image.atlas != batch.atlas {
+			dl.ranges = append(dl.ranges, drawRange{
+				atlas: cmd.Image.atlas,
+			})
+			batch = &dl.ranges[len(dl.ranges)-1]
+		}
+
+		// Dst attributes
+		bounds := cmd.Image.node.Region()
+		opts.Dsts[0] = pt(cmd.GeoM.Apply(0, 0))
+		opts.Dsts[1] = pt(cmd.GeoM.Apply(
+			float64(bounds.Dx()), 0,
+		))
+		opts.Dsts[2] = pt(cmd.GeoM.Apply(
+			0, float64(bounds.Dy()),
+		))
+		opts.Dsts[3] = pt(cmd.GeoM.Apply(
+			float64(bounds.Dx()), float64(bounds.Dy()),
+		))
+
+		// Color and source attributes
+		opts.R = cmd.ColorScale.R()
+		opts.G = cmd.ColorScale.G()
+		opts.B = cmd.ColorScale.B()
+		opts.A = cmd.ColorScale.A()
+		opts.SrcX0 = float32(bounds.Min.X)
+		opts.SrcY0 = float32(bounds.Min.Y)
+		opts.SrcX1 = float32(bounds.Max.X)
+		opts.SrcY1 = float32(bounds.Max.Y)
+
+		dl.vx, dl.ix = appendRectVerticesIndices(
+			dl.vx, dl.ix, batch.end, opts,
+		)
+
+		batch.end++
+	}
+}
+
+// DrawOptions are additional options that will be applied to
+// all draw commands from the draw list when calling Flush().
+type drawOptions struct {
+	ColorScaleMode ebiten.ColorScaleMode
+	Blend          ebiten.Blend
+	Filter         ebiten.Filter
+	Address        ebiten.Address
+	AntiAlias      bool
+}
+
+// Flush executes all the draw commands as the smallest possible
+// amount of draw calls, and then clears the list for next uses.
+func (dl *drawList) Flush(dst *ebiten.Image, opts *drawOptions) {
+	var topts *ebiten.DrawTrianglesOptions
+	if opts != nil {
+		topts = &ebiten.DrawTrianglesOptions{
+			ColorScaleMode: opts.ColorScaleMode,
+			Blend:          opts.Blend,
+			Filter:         opts.Filter,
+			Address:        opts.Address,
+			AntiAlias:      opts.AntiAlias,
+		}
+	}
+	index := 0
+	for _, r := range dl.ranges {
+		dst.DrawTriangles(
+			dl.vx[index*4:(index+r.end)*4],
+			dl.ix[index*6:(index+r.end)*6],
+			r.atlas.image,
+			topts,
+		)
+		index += r.end
+	}
+	// Clear buffers
+	dl.ranges = dl.ranges[:0]
+	dl.vx = dl.vx[:0]
+	dl.ix = dl.ix[:0]
+}

text/v2/glyph.go

@@ -18,7 +18,6 @@ import (
 	"math"
 	"sync"
 
-	"github.com/hajimehoshi/ebiten/v2"
 	"github.com/hajimehoshi/ebiten/v2/internal/hook"
 )
 
@@ -38,17 +37,18 @@ func init() {
 }
 
 type glyphImageCacheEntry struct {
-	image *ebiten.Image
+	image *glyphImage
 	atime int64
 }
 
 type glyphImageCache[Key comparable] struct {
+	atlas *glyphAtlas
 	cache map[Key]*glyphImageCacheEntry
 	atime int64
 	m     sync.Mutex
 }
 
-func (g *glyphImageCache[Key]) getOrCreate(face Face, key Key, create func() *ebiten.Image) *ebiten.Image {
+func (g *glyphImageCache[Key]) getOrCreate(face Face, key Key, create func(a *glyphAtlas) *glyphImage) *glyphImage {
 	g.m.Lock()
 	defer g.m.Unlock()
 
@@ -61,10 +61,11 @@ func (g *glyphImageCache[Key]) getOrCreate(face Face, key Key, create func() *eb
 	}
 
 	if g.cache == nil {
+		g.atlas = newGlyphAtlas()
 		g.cache = map[Key]*glyphImageCacheEntry{}
 	}
 
-	img := create()
+	img := create(g.atlas)
 	e = &glyphImageCacheEntry{
 		image: img,
 	}
@@ -91,6 +92,7 @@ func (g *glyphImageCache[Key]) getOrCreate(face Face, key Key, create func() *eb
 					continue
 				}
 				delete(g.cache, key)
+				g.atlas.Free(e.image)
 			}
 		}
 	}

text/v2/gotext.go

@@ -325,11 +325,16 @@ func (g *GoTextFace) appendGlyphsForLine(glyphs []Glyph, line string, indexOffse
 		img, imgX, imgY := g.glyphImage(glyph, o)
 		// Append a glyph even if img is nil.
 		// This is necessary to return index information for control characters.
+		var ebitenImage *ebiten.Image
+		if img != nil {
+			ebitenImage = img.Image()
+		}
 		glyphs = append(glyphs, Glyph{
+			img:               img,
 			StartIndexInBytes: indexOffset + glyph.startIndex,
 			EndIndexInBytes:   indexOffset + glyph.endIndex,
 			GID:               uint32(glyph.shapingGlyph.GlyphID),
-			Image:             img,
+			Image:             ebitenImage,
 			X:                 float64(imgX),
 			Y:                 float64(imgY),
 			OriginX:           fixed26_6ToFloat64(origin.X),
@@ -346,7 +351,7 @@ func (g *GoTextFace) appendGlyphsForLine(glyphs []Glyph, line string, indexOffse
 	return glyphs
 }
 
-func (g *GoTextFace) glyphImage(glyph glyph, origin fixed.Point26_6) (*ebiten.Image, int, int) {
+func (g *GoTextFace) glyphImage(glyph glyph, origin fixed.Point26_6) (*glyphImage, int, int) {
 	if g.direction().isHorizontal() {
 		origin.X = adjustGranularity(origin.X, g)
 		origin.Y &^= ((1 << 6) - 1)
@@ -366,8 +371,8 @@ func (g *GoTextFace) glyphImage(glyph glyph, origin fixed.Point26_6) (*ebiten.Im
 		yoffset:    subpixelOffset.Y,
 		variations: g.ensureVariationsString(),
 	}
-	img := g.Source.getOrCreateGlyphImage(g, key, func() *ebiten.Image {
-		return segmentsToImage(glyph.scaledSegments, subpixelOffset, b)
+	img := g.Source.getOrCreateGlyphImage(g, key, func(a *glyphAtlas) *glyphImage {
+		return segmentsToImage(a, glyph.scaledSegments, subpixelOffset, b)
 	})
 
 	imgX := (origin.X + b.Min.X).Floor()