forked from marcetin/parallelcoin
/
text.go
195 lines (181 loc) · 4.32 KB
/
text.go
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package gui
import (
"fmt"
"image"
"unicode/utf8"
"gioui.org/layout"
"gioui.org/op"
"gioui.org/op/clip"
"gioui.org/op/paint"
"gioui.org/text"
"gioui.org/unit"
"golang.org/x/image/math/fixed"
)
// Text is a widget for laying out and drawing text.
type Text struct {
*Window
// alignment specify the text alignment.
alignment text.Alignment
// maxLines limits the number of lines. Zero means no limit.
maxLines int
}
func (w *Window) Text() *Text {
return &Text{Window: w}
}
// Alignment sets the alignment for the text
func (t *Text) Alignment(alignment text.Alignment) *Text {
t.alignment = alignment
return t
}
// MaxLines sets the alignment for the text
func (t *Text) MaxLines(maxLines int) *Text {
t.maxLines = maxLines
return t
}
type lineIterator struct {
Lines []text.Line
Clip image.Rectangle
Alignment text.Alignment
Width int
Offset image.Point
y, prevDesc fixed.Int26_6
txtOff int
}
func (l *lineIterator) Next() (text.Layout, image.Point, bool) {
for len(l.Lines) > 0 {
line := l.Lines[0]
l.Lines = l.Lines[1:]
x := align(l.Alignment, line.Width, l.Width) + fixed.I(l.Offset.X)
l.y += l.prevDesc + line.Ascent
l.prevDesc = line.Descent
// Align baseline and line start to the pixel grid.
off := fixed.Point26_6{X: fixed.I(x.Floor()), Y: fixed.I(l.y.Ceil())}
l.y = off.Y
off.Y += fixed.I(l.Offset.Y)
if (off.Y + line.Bounds.Min.Y).Floor() > l.Clip.Max.Y {
break
}
lo := line.Layout
start := l.txtOff
l.txtOff += len(line.Layout.Text)
if (off.Y + line.Bounds.Max.Y).Ceil() < l.Clip.Min.Y {
continue
}
for len(lo.Advances) > 0 {
_, n := utf8.DecodeRuneInString(lo.Text)
adv := lo.Advances[0]
if (off.X + adv + line.Bounds.Max.X - line.Width).Ceil() >= l.Clip.Min.X {
break
}
off.X += adv
lo.Text = lo.Text[n:]
lo.Advances = lo.Advances[1:]
start += n
}
end := start
endx := off.X
rn := 0
for n, r := range lo.Text {
if (endx + line.Bounds.Min.X).Floor() > l.Clip.Max.X {
lo.Advances = lo.Advances[:rn]
lo.Text = lo.Text[:n]
break
}
end += utf8.RuneLen(r)
endx += lo.Advances[rn]
rn++
}
offf := image.Point{X: off.X.Floor(), Y: off.Y.Floor()}
return lo, offf, true
}
return text.Layout{}, image.Point{}, false
}
func linesDimens(lines []text.Line) layout.Dimensions {
var width fixed.Int26_6
var h int
var baseline int
if len(lines) > 0 {
baseline = lines[0].Ascent.Ceil()
var prevDesc fixed.Int26_6
for _, l := range lines {
h += (prevDesc + l.Ascent).Ceil()
prevDesc = l.Descent
if l.Width > width {
width = l.Width
}
}
h += lines[len(lines)-1].Descent.Ceil()
}
w := width.Ceil()
return layout.Dimensions{
Size: image.Point{
X: w,
Y: h,
},
Baseline: h - baseline,
}
}
func (t *Text) Fn(gtx layout.Context, s text.Shaper, font text.Font, size unit.Value, txt string) layout.Dimensions {
cs := gtx.Constraints
textSize := fixed.I(gtx.Px(size))
lines := s.LayoutString(font, textSize, cs.Max.X, txt)
if max := t.maxLines; max > 0 && len(lines) > max {
lines = lines[:max]
}
dims := linesDimens(lines)
dims.Size = cs.Constrain(dims.Size)
cl := textPadding(lines)
cl.Max = cl.Max.Add(dims.Size)
it := lineIterator{
Lines: lines,
Clip: cl,
Alignment: t.alignment,
Width: dims.Size.X,
}
for {
l, off, ok := it.Next()
if !ok {
break
}
stack := op.Push(gtx.Ops)
op.Offset(layout.FPt(off)).Add(gtx.Ops)
s.Shape(font, textSize, l).Add(gtx.Ops)
clip.Rect(cl.Sub(off)).Add(gtx.Ops)
paint.PaintOp{}.Add(gtx.Ops)
stack.Pop()
}
return dims
}
func textPadding(lines []text.Line) (padding image.Rectangle) {
if len(lines) == 0 {
return
}
first := lines[0]
if d := first.Ascent + first.Bounds.Min.Y; d < 0 {
padding.Min.Y = d.Ceil()
}
last := lines[len(lines)-1]
if d := last.Bounds.Max.Y - last.Descent; d > 0 {
padding.Max.Y = d.Ceil()
}
if d := first.Bounds.Min.X; d < 0 {
padding.Min.X = d.Ceil()
}
if d := first.Bounds.Max.X - first.Width; d > 0 {
padding.Max.X = d.Ceil()
}
return
}
func align(align text.Alignment, width fixed.Int26_6, maxWidth int) fixed.Int26_6 {
mw := fixed.I(maxWidth)
switch align {
case text.Middle:
return fixed.I(((mw - width) / 2).Floor())
case text.End:
return fixed.I((mw - width).Floor())
case text.Start:
return 0
default:
panic(fmt.Errorf("unknown alignment %v", align))
}
}