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Accurate vertical positioning of text+return fractional bearing/descent

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This commit is contained in:
bloeys
2022-07-10 12:42:31 +04:00
parent cb2ead0907
commit 7fa94806a4
5 changed files with 105 additions and 32 deletions
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35
glyphs/font_atlas.go
View File

@ -22,8 +22,8 @@ type FontAtlas struct {
Glyphs map[rune]FontAtlasGlyph
//Advance is global to the atlas because we only support monospaced fonts
Advance int
LineHeight int
Advance float32
LineHeight float32
}
type FontAtlasGlyph struct {
@ -120,16 +120,13 @@ func NewFontAtlasFromFont(f *truetype.Font, face font.Face, pointSize uint) (*Fo
}
//Create atlas
// atlasSizeXF32 := float32(atlasSizeX)
// atlasSizeYF32 := float32(atlasSizeY)
atlas := &FontAtlas{
Font: f,
Img: image.NewRGBA(image.Rect(0, 0, atlasSizeX, atlasSizeY)),
Glyphs: make(map[rune]FontAtlasGlyph, len(glyphs)),
Advance: charAdv - charPaddingX,
LineHeight: lineHeight,
// SizeUV: *gglm.NewVec2(float32(charAdv-charPaddingX)/atlasSizeXF32, float32(lineHeight)/atlasSizeYF32),
Advance: float32(charAdv - charPaddingX),
LineHeight: float32(lineHeight),
}
//Clear background to black
@ -145,9 +142,9 @@ func NewFontAtlasFromFont(f *truetype.Font, face font.Face, pointSize uint) (*Fo
charPaddingYFixed := fixed.I(charPaddingY)
charsOnLine := 0
drawer.Dot = fixed.P(atlas.Advance+charPaddingX, lineHeight)
const drawBoundingBoxes bool = false
drawer.Dot = fixed.P(int(atlas.Advance+charPaddingX), lineHeight)
const drawBoundingBoxes bool = false
for currGlyphCount, g := range glyphs {
gBounds, gAdvance, _ := face.GlyphBounds(g)
@ -172,10 +169,10 @@ func NewFontAtlasFromFont(f *truetype.Font, face font.Face, pointSize uint) (*Fo
SizeU: float32(gBotRight.X - gTopLeft.X),
SizeV: float32(gBotRight.Y - gTopLeft.Y),
Ascent: float32(ascentAbsFixed.Ceil()),
Descent: float32(descentAbsFixed.Ceil()),
BearingX: float32(bearingX.Ceil()),
Advance: float32(gAdvance.Ceil()),
Ascent: I26_6ToF32(ascentAbsFixed),
Descent: I26_6ToF32(descentAbsFixed),
BearingX: I26_6ToF32(bearingX),
Advance: I26_6ToF32(gAdvance),
}
imgRect, mask, maskp, _, _ := face.Glyph(drawer.Dot, g)
@ -197,7 +194,7 @@ func NewFontAtlasFromFont(f *truetype.Font, face font.Face, pointSize uint) (*Fo
if charsOnLine == charsPerLine || currGlyphCount == len(glyphs)-1 {
charsOnLine = 0
drawer.Dot.X = fixed.I(atlas.Advance) + charPaddingXFixed
drawer.Dot.X = fixed.I(int(atlas.Advance)) + charPaddingXFixed
drawer.Dot.Y += lineHeightFixed + charPaddingYFixed
}
}
@ -252,6 +249,16 @@ func DrawRect(img *image.RGBA, rect image.Rectangle, color color.NRGBA) {
}
}
func I26_6ToF32(x fixed.Int26_6) float32 {
const lower6BitMask = 1<<6 - 1
if x > 0 {
return float32(x.Floor()) + float32(x&lower6BitMask)/64
} else {
return float32(x.Floor()) - float32(x&lower6BitMask)/64
}
}
func DrawVerticalLine(img *image.RGBA, posX int, color color.NRGBA) {
rowLength := img.Stride

47
glyphs/glyphs.go
View File

@ -2,6 +2,8 @@ package glyphs
import (
"errors"
"fmt"
"math"
"unicode"
"github.com/bloeys/gglm/gglm"
@ -68,11 +70,8 @@ func (gr *GlyphRend) DrawTextOpenGLAbs(text string, screenPos *gglm.Vec3, color
}
pos := screenPos.Clone()
advanceF32 := float32(gr.Atlas.Advance)
lineHeightF32 := float32(gr.Atlas.LineHeight)
bufIndex := gr.GlyphCount * floatsPerGlyph
for runIndex := 0; runIndex < len(runs); runIndex++ {
run := &runs[runIndex]
@ -81,14 +80,14 @@ func (gr *GlyphRend) DrawTextOpenGLAbs(text string, screenPos *gglm.Vec3, color
if run.IsLtr {
for i := 0; i < len(run.Runes); i++ {
gr.drawRune(run, i, prevRune, screenPos, pos, color, advanceF32, lineHeightF32, &bufIndex)
gr.drawRune(run, i, prevRune, screenPos, pos, color, lineHeightF32, &bufIndex)
prevRune = run.Runes[i]
}
} else {
for i := len(run.Runes) - 1; i >= 0; i-- {
gr.drawRune(run, i, prevRune, screenPos, pos, color, advanceF32, lineHeightF32, &bufIndex)
gr.drawRune(run, i, prevRune, screenPos, pos, color, lineHeightF32, &bufIndex)
prevRune = run.Runes[i]
}
@ -96,21 +95,20 @@ func (gr *GlyphRend) DrawTextOpenGLAbs(text string, screenPos *gglm.Vec3, color
}
}
func (gr *GlyphRend) drawRune(run *TextRun, i int, prevRune rune, screenPos, pos *gglm.Vec3, color *gglm.Vec4, advanceF32, lineHeightF32 float32, bufIndex *uint32) {
var PrintPositions bool
func (gr *GlyphRend) drawRune(run *TextRun, i int, prevRune rune, screenPos, pos *gglm.Vec3, color *gglm.Vec4, lineHeightF32 float32, bufIndex *uint32) {
r := run.Runes[i]
if r == '\n' {
screenPos.SetY(screenPos.Y() - lineHeightF32)
*pos = *screenPos.Clone()
// prevRune = r
return
} else if r == ' ' {
pos.AddX(advanceF32)
// prevRune = r
pos.AddX(gr.Atlas.Advance)
return
} else if r == '\t' {
pos.AddX(advanceF32 * float32(gr.SpacesPerTab))
// prevRune = r
pos.AddX(gr.Atlas.Advance * float32(gr.SpacesPerTab))
return
}
@ -135,8 +133,16 @@ func (gr *GlyphRend) drawRune(run *TextRun, i int, prevRune rune, screenPos, pos
//We must adjust char positioning according to: https://developer.apple.com/library/archive/documentation/TextFonts/Conceptual/CocoaTextArchitecture/Art/glyph_metrics_2x.png
drawPos := *pos
drawPos.SetX(drawPos.X() + g.BearingX)
drawPos.SetY(drawPos.Y() - g.Descent)
//The flooring to an integer pixel must happen AFTER the (potentially) fractional adjustments have been made.
//This is what the truetype face.Rasterizer does and seems to give good results
drawPos.SetX(floorF32(drawPos.X() + g.BearingX))
drawPos.SetY(floorF32(drawPos.Y() - g.Descent))
if PrintPositions {
oldXY := gglm.NewVec2(pos.X(), pos.Y())
newXY := gglm.NewVec2(drawPos.X(), drawPos.Y())
fmt.Printf("char=%s; PosBefore=%s, PosAfter=%s; Bearing/Decent=(%f, %f)\n", string(r), oldXY.String(), newXY.String(), g.BearingX, g.Descent)
}
//Add the glyph information to the vbo
//UV
@ -168,7 +174,8 @@ func (gr *GlyphRend) drawRune(run *TextRun, i int, prevRune rune, screenPos, pos
*bufIndex += 2
gr.GlyphCount++
pos.AddX(g.Advance)
pos.AddX(gr.Atlas.Advance)
// pos.AddX(g.Advance)
//If we fill the buffer we issue a draw call
if gr.GlyphCount == MaxGlyphsPerBatch {
@ -177,6 +184,18 @@ func (gr *GlyphRend) drawRune(run *TextRun, i int, prevRune rune, screenPos, pos
}
}
func roundF32(x float32) float32 {
return float32(math.Round(float64(x)))
}
func ceilF32(x float32) float32 {
return float32(math.Ceil(float64(x)))
}
func floorF32(x float32) float32 {
return float32(math.Floor(float64(x)))
}
type TextRun struct {
Runes []rune
IsLtr bool