225 lines
6.3 KiB
Go
225 lines
6.3 KiB
Go
// Package pdf renders laid-out pages to PDF. It writes the file by hand
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// using the standard Courier fonts that every PDF reader ships with, so no
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// font is embedded and there is no external dependency.
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package pdf
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import (
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"bytes"
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"compress/zlib"
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"fmt"
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"io"
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"math"
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"strings"
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"unicode/utf16"
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"plotzilla/internal/layout"
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"plotzilla/internal/screenplay"
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)
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type Options struct {
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Title string
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Author string
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Paper screenplay.Paper
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// Revisions are the document's revision sets. When set, a page whose
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// text was revised gets a header naming its revision, and its revised
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// lines an asterisk in the right margin.
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Revisions []screenplay.Revision
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}
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const (
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fontSize = 12.0
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ptPerIn = 72.0
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)
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var fontNames = []string{"Courier", "Courier-Bold", "Courier-Oblique", "Courier-BoldOblique"}
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// Render writes pages to w. The title page, if any, must be the first page
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// and have Number 0 so that it is not numbered.
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func Render(w io.Writer, pages []layout.Page, opt Options) error {
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geo := layout.PaperGeometry(opt.Paper)
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var objs [][]byte // objs[i] is object number i+1
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add := func(s string) int {
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objs = append(objs, []byte(s))
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return len(objs)
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}
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// 1: catalog, 2: page tree, 3-6: fonts, 7: info. Pages follow.
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add("<< /Type /Catalog /Pages 2 0 R >>")
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add("") // page tree, filled once the kids are known
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for _, f := range fontNames {
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add("<< /Type /Font /Subtype /Type1 /BaseFont /" + f + " /Encoding /WinAnsiEncoding >>")
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}
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add(fmt.Sprintf("<< /Title %s /Author %s /Creator (Plotzilla) /Producer (Plotzilla) >>", textString(opt.Title), textString(opt.Author)))
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var kids []string
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for _, pg := range pages {
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stream, err := deflate(pageContent(pg, geo, opt.Revisions))
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if err != nil {
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return err
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}
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content := add(fmt.Sprintf("<< /Length %d /Filter /FlateDecode >>\nstream\n%s\nendstream", len(stream), stream))
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page := add(fmt.Sprintf("<< /Type /Page /Parent 2 0 R /MediaBox [0 0 %g %g] "+
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"/Resources << /Font << /F1 3 0 R /F2 4 0 R /F3 5 0 R /F4 6 0 R >> >> /Contents %d 0 R >>",
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points(geo.Width), points(geo.Height), content))
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kids = append(kids, fmt.Sprintf("%d 0 R", page))
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}
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objs[1] = []byte(fmt.Sprintf("<< /Type /Pages /Kids [%s] /Count %d >>", strings.Join(kids, " "), len(kids)))
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var buf bytes.Buffer
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buf.WriteString("%PDF-1.4\n%\xe2\xe3\xcf\xd3\n")
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offsets := make([]int, len(objs))
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for i, o := range objs {
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offsets[i] = buf.Len()
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fmt.Fprintf(&buf, "%d 0 obj\n", i+1)
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buf.Write(o)
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buf.WriteString("\nendobj\n")
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}
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xref := buf.Len()
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fmt.Fprintf(&buf, "xref\n0 %d\n0000000000 65535 f \n", len(objs)+1)
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for _, off := range offsets {
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fmt.Fprintf(&buf, "%010d 00000 n \n", off)
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}
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fmt.Fprintf(&buf, "trailer\n<< /Size %d /Root 1 0 R /Info 7 0 R >>\nstartxref\n%d\n%%%%EOF\n", len(objs)+1, xref)
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_, err := w.Write(buf.Bytes())
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return err
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}
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// points converts inches to PDF points, rounded to 1/100 pt.
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func points(in float64) float64 { return math.Round(in*ptPerIn*100) / 100 }
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// baseline returns the PDF y coordinate of the baseline of a body row.
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func baseline(geo layout.Geometry, row int) float64 {
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top := (geo.Height - layout.TopMargin) * ptPerIn
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return top - float64(row)*fontSize - 9
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}
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func text(b *bytes.Buffer, x, y float64, s string) {
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fmt.Fprintf(b, "BT /F1 12 Tf %.2f %.2f Td %s Tj ET\n", x, y, pdfString(s))
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}
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func pageContent(pg layout.Page, geo layout.Geometry, revisions []screenplay.Revision) []byte {
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var b bytes.Buffer
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header := (geo.Height-0.5)*ptPerIn - 9
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if pg.Number > 0 && pg.Label != "" && pg.Label != "1" {
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num := pg.Label + "."
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text(&b, layout.RightEdge*ptPerIn-float64(len([]rune(num)))*fontSize*0.6, header, num)
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}
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// A revised page names its revision; its latest changes are starred.
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rev := pg.Rev()
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if rev > len(revisions) {
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rev = 0
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}
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if rev > 0 {
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r := revisions[rev-1]
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label := r.Name + " Revision"
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if r.Date != "" {
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label += " - " + r.Date
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}
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text(&b, 1.5*ptPerIn, header, label)
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}
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for _, ln := range pg.Lines {
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y := baseline(geo, ln.Row)
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x := ln.X * ptPerIn
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if ln.SceneNumber != "" {
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text(&b, 0.75*ptPerIn, y, ln.SceneNumber)
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text(&b, geo.SceneNumber*ptPerIn, y, ln.SceneNumber)
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}
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if rev > 0 && ln.Rev == rev {
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text(&b, geo.RevisionMark*ptPerIn, y, "*")
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}
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fmt.Fprintf(&b, "BT %.2f %.2f Td ", x, y)
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cursor := x
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var underlines [][2]float64
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for _, s := range ln.Segments {
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font := 1
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if s.Bold {
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font++
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}
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if s.Italic {
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font += 2
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}
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width := float64(len([]rune(s.Text))) * fontSize * 0.6
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if s.Underline {
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underlines = append(underlines, [2]float64{cursor, cursor + width})
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}
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cursor += width
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fmt.Fprintf(&b, "/F%d 12 Tf %s Tj ", font, pdfString(s.Text))
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}
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b.WriteString("ET\n")
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for _, u := range underlines {
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fmt.Fprintf(&b, "0.6 w %.2f %.2f m %.2f %.2f l S\n", u[0], y-1.8, u[1], y-1.8)
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}
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}
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return b.Bytes()
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}
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func deflate(data []byte) ([]byte, error) {
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var b bytes.Buffer
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zw := zlib.NewWriter(&b)
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if _, err := zw.Write(data); err != nil {
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return nil, err
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}
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if err := zw.Close(); err != nil {
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return nil, err
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}
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return b.Bytes(), nil
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}
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// pdfString encodes s as a WinAnsi literal string for the Courier fonts.
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func pdfString(s string) string {
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var b strings.Builder
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b.WriteByte('(')
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for _, r := range s {
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c := winAnsi(r)
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if c == '(' || c == ')' || c == '\\' {
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b.WriteByte('\\')
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}
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b.WriteByte(c)
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}
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b.WriteByte(')')
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return b.String()
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}
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// textString encodes s for the document info dictionary.
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func textString(s string) string {
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ascii := true
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for _, r := range s {
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if r > 0x7e || r < 0x20 {
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ascii = false
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break
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}
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}
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if ascii {
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return pdfString(s)
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}
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var b strings.Builder
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b.WriteString("<FEFF")
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for _, u := range utf16.Encode([]rune(s)) {
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fmt.Fprintf(&b, "%04X", u)
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}
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b.WriteString(">")
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return b.String()
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}
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var cp1252 = map[rune]byte{
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'€': 0x80, '‚': 0x82, 'ƒ': 0x83, '„': 0x84, '…': 0x85, '†': 0x86, '‡': 0x87,
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'ˆ': 0x88, '‰': 0x89, 'Š': 0x8a, '‹': 0x8b, 'Œ': 0x8c, 'Ž': 0x8e,
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'‘': 0x91, '’': 0x92, '“': 0x93, '”': 0x94, '•': 0x95, '–': 0x96, '—': 0x97,
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'˜': 0x98, '™': 0x99, 'š': 0x9a, '›': 0x9b, 'œ': 0x9c, 'ž': 0x9e, 'Ÿ': 0x9f,
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}
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func winAnsi(r rune) byte {
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switch {
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case r >= 0x20 && r < 0x7f:
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return byte(r)
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case r >= 0xa0 && r <= 0xff:
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return byte(r)
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}
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if c, ok := cp1252[r]; ok {
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return c
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}
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if r == ' ' || r == ' ' {
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return ' ' // narrow spaces used before French punctuation
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}
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return '?'
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}
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