456 lines
13 KiB
Go
456 lines
13 KiB
Go
package html
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import (
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"fmt"
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"html"
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"io"
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"sort"
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"strings"
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"github.com/alecthomas/chroma"
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)
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// Option sets an option of the HTML formatter.
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type Option func(f *Formatter)
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// Standalone configures the HTML formatter for generating a standalone HTML document.
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func Standalone(b bool) Option { return func(f *Formatter) { f.standalone = b } }
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// ClassPrefix sets the CSS class prefix.
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func ClassPrefix(prefix string) Option { return func(f *Formatter) { f.prefix = prefix } }
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// WithClasses emits HTML using CSS classes, rather than inline styles.
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func WithClasses(b bool) Option { return func(f *Formatter) { f.Classes = b } }
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// WithAllClasses disables an optimisation that omits redundant CSS classes.
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func WithAllClasses(b bool) Option { return func(f *Formatter) { f.allClasses = b } }
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// TabWidth sets the number of characters for a tab. Defaults to 8.
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func TabWidth(width int) Option { return func(f *Formatter) { f.tabWidth = width } }
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// PreventSurroundingPre prevents the surrounding pre tags around the generated code.
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func PreventSurroundingPre(b bool) Option {
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return func(f *Formatter) {
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if b {
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f.preWrapper = nopPreWrapper
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} else {
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f.preWrapper = defaultPreWrapper
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}
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}
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}
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// WithPreWrapper allows control of the surrounding pre tags.
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func WithPreWrapper(wrapper PreWrapper) Option {
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return func(f *Formatter) {
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f.preWrapper = wrapper
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}
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}
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// WithLineNumbers formats output with line numbers.
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func WithLineNumbers(b bool) Option {
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return func(f *Formatter) {
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f.lineNumbers = b
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}
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}
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// LineNumbersInTable will, when combined with WithLineNumbers, separate the line numbers
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// and code in table td's, which make them copy-and-paste friendly.
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func LineNumbersInTable(b bool) Option {
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return func(f *Formatter) {
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f.lineNumbersInTable = b
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}
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}
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// LinkableLineNumbers decorates the line numbers HTML elements with an "id"
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// attribute so they can be linked.
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func LinkableLineNumbers(b bool, prefix string) Option {
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return func(f *Formatter) {
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f.linkableLineNumbers = b
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f.lineNumbersIDPrefix = prefix
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}
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}
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// HighlightLines higlights the given line ranges with the Highlight style.
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//
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// A range is the beginning and ending of a range as 1-based line numbers, inclusive.
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func HighlightLines(ranges [][2]int) Option {
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return func(f *Formatter) {
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f.highlightRanges = ranges
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sort.Sort(f.highlightRanges)
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}
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}
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// BaseLineNumber sets the initial number to start line numbering at. Defaults to 1.
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func BaseLineNumber(n int) Option {
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return func(f *Formatter) {
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f.baseLineNumber = n
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}
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}
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// New HTML formatter.
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func New(options ...Option) *Formatter {
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f := &Formatter{
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baseLineNumber: 1,
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preWrapper: defaultPreWrapper,
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}
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for _, option := range options {
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option(f)
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}
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return f
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}
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// PreWrapper defines the operations supported in WithPreWrapper.
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type PreWrapper interface {
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// Start is called to write a start <pre> element.
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// The code flag tells whether this block surrounds
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// highlighted code. This will be false when surrounding
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// line numbers.
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Start(code bool, styleAttr string) string
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// End is called to write the end </pre> element.
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End(code bool) string
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}
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type preWrapper struct {
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start func(code bool, styleAttr string) string
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end func(code bool) string
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}
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func (p preWrapper) Start(code bool, styleAttr string) string {
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return p.start(code, styleAttr)
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}
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func (p preWrapper) End(code bool) string {
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return p.end(code)
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}
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var (
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nopPreWrapper = preWrapper{
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start: func(code bool, styleAttr string) string { return "" },
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end: func(code bool) string { return "" },
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}
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defaultPreWrapper = preWrapper{
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start: func(code bool, styleAttr string) string {
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return fmt.Sprintf(`<pre tabindex="0"%s>`, styleAttr)
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},
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end: func(code bool) string {
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return "</pre>"
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},
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}
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)
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// Formatter that generates HTML.
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type Formatter struct {
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standalone bool
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prefix string
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Classes bool // Exported field to detect when classes are being used
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allClasses bool
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preWrapper PreWrapper
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tabWidth int
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lineNumbers bool
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lineNumbersInTable bool
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linkableLineNumbers bool
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lineNumbersIDPrefix string
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highlightRanges highlightRanges
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baseLineNumber int
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}
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type highlightRanges [][2]int
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func (h highlightRanges) Len() int { return len(h) }
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func (h highlightRanges) Swap(i, j int) { h[i], h[j] = h[j], h[i] }
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func (h highlightRanges) Less(i, j int) bool { return h[i][0] < h[j][0] }
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func (f *Formatter) Format(w io.Writer, style *chroma.Style, iterator chroma.Iterator) (err error) {
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return f.writeHTML(w, style, iterator.Tokens())
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}
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// We deliberately don't use html/template here because it is two orders of magnitude slower (benchmarked).
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//
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// OTOH we need to be super careful about correct escaping...
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func (f *Formatter) writeHTML(w io.Writer, style *chroma.Style, tokens []chroma.Token) (err error) { // nolint: gocyclo
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css := f.styleToCSS(style)
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if !f.Classes {
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for t, style := range css {
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css[t] = compressStyle(style)
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}
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}
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if f.standalone {
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fmt.Fprint(w, "<html>\n")
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if f.Classes {
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fmt.Fprint(w, "<style type=\"text/css\">\n")
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err = f.WriteCSS(w, style)
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if err != nil {
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return err
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}
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fmt.Fprintf(w, "body { %s; }\n", css[chroma.Background])
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fmt.Fprint(w, "</style>")
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}
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fmt.Fprintf(w, "<body%s>\n", f.styleAttr(css, chroma.Background))
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}
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wrapInTable := f.lineNumbers && f.lineNumbersInTable
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lines := chroma.SplitTokensIntoLines(tokens)
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lineDigits := len(fmt.Sprintf("%d", f.baseLineNumber+len(lines)-1))
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highlightIndex := 0
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if wrapInTable {
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// List line numbers in its own <td>
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fmt.Fprintf(w, "<div%s>\n", f.styleAttr(css, chroma.Background))
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fmt.Fprintf(w, "<table%s><tr>", f.styleAttr(css, chroma.LineTable))
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fmt.Fprintf(w, "<td%s>\n", f.styleAttr(css, chroma.LineTableTD))
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fmt.Fprintf(w, f.preWrapper.Start(false, f.styleAttr(css, chroma.Background)))
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for index := range lines {
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line := f.baseLineNumber + index
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highlight, next := f.shouldHighlight(highlightIndex, line)
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if next {
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highlightIndex++
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}
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if highlight {
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fmt.Fprintf(w, "<span%s>", f.styleAttr(css, chroma.LineHighlight))
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}
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fmt.Fprintf(w, "<span%s%s>%s\n</span>", f.styleAttr(css, chroma.LineNumbersTable), f.lineIDAttribute(line), f.lineTitleWithLinkIfNeeded(lineDigits, line))
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if highlight {
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fmt.Fprintf(w, "</span>")
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}
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}
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fmt.Fprint(w, f.preWrapper.End(false))
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fmt.Fprint(w, "</td>\n")
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fmt.Fprintf(w, "<td%s>\n", f.styleAttr(css, chroma.LineTableTD, "width:100%"))
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}
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fmt.Fprintf(w, f.preWrapper.Start(true, f.styleAttr(css, chroma.Background)))
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highlightIndex = 0
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for index, tokens := range lines {
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// 1-based line number.
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line := f.baseLineNumber + index
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highlight, next := f.shouldHighlight(highlightIndex, line)
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if next {
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highlightIndex++
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}
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if highlight {
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fmt.Fprintf(w, "<span%s>", f.styleAttr(css, chroma.LineHighlight))
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}
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if f.lineNumbers && !wrapInTable {
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fmt.Fprintf(w, "<span%s%s>%s</span>", f.styleAttr(css, chroma.LineNumbers), f.lineIDAttribute(line), f.lineTitleWithLinkIfNeeded(lineDigits, line))
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}
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for _, token := range tokens {
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html := html.EscapeString(token.String())
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attr := f.styleAttr(css, token.Type)
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if attr != "" {
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html = fmt.Sprintf("<span%s>%s</span>", attr, html)
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}
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fmt.Fprint(w, html)
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}
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if highlight {
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fmt.Fprintf(w, "</span>")
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}
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}
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fmt.Fprintf(w, f.preWrapper.End(true))
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if wrapInTable {
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fmt.Fprint(w, "</td></tr></table>\n")
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fmt.Fprint(w, "</div>\n")
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}
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if f.standalone {
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fmt.Fprint(w, "\n</body>\n")
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fmt.Fprint(w, "</html>\n")
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}
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return nil
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}
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func (f *Formatter) lineIDAttribute(line int) string {
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if !f.linkableLineNumbers {
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return ""
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}
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return fmt.Sprintf(" id=\"%s\"", f.lineID(line))
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}
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func (f *Formatter) lineTitleWithLinkIfNeeded(lineDigits, line int) string {
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title := fmt.Sprintf("%*d", lineDigits, line)
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if !f.linkableLineNumbers {
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return title
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}
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return fmt.Sprintf("<a style=\"outline: none; text-decoration:none; color:inherit\" href=\"#%s\">%s</a>", f.lineID(line), title)
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}
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func (f *Formatter) lineID(line int) string {
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return fmt.Sprintf("%s%d", f.lineNumbersIDPrefix, line)
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}
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func (f *Formatter) shouldHighlight(highlightIndex, line int) (bool, bool) {
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next := false
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for highlightIndex < len(f.highlightRanges) && line > f.highlightRanges[highlightIndex][1] {
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highlightIndex++
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next = true
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}
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if highlightIndex < len(f.highlightRanges) {
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hrange := f.highlightRanges[highlightIndex]
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if line >= hrange[0] && line <= hrange[1] {
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return true, next
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}
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}
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return false, next
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}
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func (f *Formatter) class(t chroma.TokenType) string {
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for t != 0 {
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if cls, ok := chroma.StandardTypes[t]; ok {
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if cls != "" {
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return f.prefix + cls
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}
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return ""
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}
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t = t.Parent()
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}
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if cls := chroma.StandardTypes[t]; cls != "" {
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return f.prefix + cls
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}
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return ""
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}
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func (f *Formatter) styleAttr(styles map[chroma.TokenType]string, tt chroma.TokenType, extraCSS ...string) string {
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if f.Classes {
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cls := f.class(tt)
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if cls == "" {
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return ""
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}
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return fmt.Sprintf(` class="%s"`, cls)
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}
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if _, ok := styles[tt]; !ok {
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tt = tt.SubCategory()
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if _, ok := styles[tt]; !ok {
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tt = tt.Category()
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if _, ok := styles[tt]; !ok {
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return ""
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}
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}
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}
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css := []string{styles[tt]}
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css = append(css, extraCSS...)
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return fmt.Sprintf(` style="%s"`, strings.Join(css, ";"))
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}
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func (f *Formatter) tabWidthStyle() string {
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if f.tabWidth != 0 && f.tabWidth != 8 {
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return fmt.Sprintf("; -moz-tab-size: %[1]d; -o-tab-size: %[1]d; tab-size: %[1]d", f.tabWidth)
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}
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return ""
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}
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// WriteCSS writes CSS style definitions (without any surrounding HTML).
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func (f *Formatter) WriteCSS(w io.Writer, style *chroma.Style) error {
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css := f.styleToCSS(style)
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// Special-case background as it is mapped to the outer ".chroma" class.
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if _, err := fmt.Fprintf(w, "/* %s */ .%schroma { %s }\n", chroma.Background, f.prefix, css[chroma.Background]); err != nil {
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return err
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}
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// Special-case code column of table to expand width.
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if f.lineNumbers && f.lineNumbersInTable {
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if _, err := fmt.Fprintf(w, "/* %s */ .%schroma .%s:last-child { width: 100%%; }",
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chroma.LineTableTD, f.prefix, f.class(chroma.LineTableTD)); err != nil {
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return err
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}
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}
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// Special-case line number highlighting when targeted.
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if f.lineNumbers || f.lineNumbersInTable {
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targetedLineCSS := StyleEntryToCSS(style.Get(chroma.LineHighlight))
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for _, tt := range []chroma.TokenType{chroma.LineNumbers, chroma.LineNumbersTable} {
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fmt.Fprintf(w, "/* %s targeted by URL anchor */ .%schroma .%s:target { %s }\n", tt, f.prefix, f.class(tt), targetedLineCSS)
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}
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}
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tts := []int{}
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for tt := range css {
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tts = append(tts, int(tt))
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}
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sort.Ints(tts)
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for _, ti := range tts {
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tt := chroma.TokenType(ti)
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if tt == chroma.Background {
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continue
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}
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class := f.class(tt)
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if class == "" {
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continue
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}
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styles := css[tt]
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if _, err := fmt.Fprintf(w, "/* %s */ .%schroma .%s { %s }\n", tt, f.prefix, class, styles); err != nil {
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return err
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}
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}
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return nil
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}
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func (f *Formatter) styleToCSS(style *chroma.Style) map[chroma.TokenType]string {
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classes := map[chroma.TokenType]string{}
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bg := style.Get(chroma.Background)
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// Convert the style.
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for t := range chroma.StandardTypes {
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entry := style.Get(t)
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if t != chroma.Background {
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entry = entry.Sub(bg)
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}
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if !f.allClasses && entry.IsZero() {
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continue
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}
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classes[t] = StyleEntryToCSS(entry)
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}
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classes[chroma.Background] += f.tabWidthStyle()
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lineNumbersStyle := "margin-right: 0.4em; padding: 0 0.4em 0 0.4em;"
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// All rules begin with default rules followed by user provided rules
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classes[chroma.LineNumbers] = lineNumbersStyle + classes[chroma.LineNumbers]
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classes[chroma.LineNumbersTable] = lineNumbersStyle + classes[chroma.LineNumbersTable]
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classes[chroma.LineHighlight] = "display: block; width: 100%;" + classes[chroma.LineHighlight]
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classes[chroma.LineTable] = "border-spacing: 0; padding: 0; margin: 0; border: 0; width: auto; overflow: auto; display: block;" + classes[chroma.LineTable]
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classes[chroma.LineTableTD] = "vertical-align: top; padding: 0; margin: 0; border: 0;" + classes[chroma.LineTableTD]
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return classes
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}
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// StyleEntryToCSS converts a chroma.StyleEntry to CSS attributes.
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func StyleEntryToCSS(e chroma.StyleEntry) string {
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styles := []string{}
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if e.Colour.IsSet() {
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styles = append(styles, "color: "+e.Colour.String())
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}
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if e.Background.IsSet() {
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styles = append(styles, "background-color: "+e.Background.String())
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}
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if e.Bold == chroma.Yes {
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styles = append(styles, "font-weight: bold")
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}
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if e.Italic == chroma.Yes {
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styles = append(styles, "font-style: italic")
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}
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if e.Underline == chroma.Yes {
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styles = append(styles, "text-decoration: underline")
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}
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return strings.Join(styles, "; ")
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}
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// Compress CSS attributes - remove spaces, transform 6-digit colours to 3.
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func compressStyle(s string) string {
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parts := strings.Split(s, ";")
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out := []string{}
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for _, p := range parts {
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p = strings.Join(strings.Fields(p), " ")
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p = strings.Replace(p, ": ", ":", 1)
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if strings.Contains(p, "#") {
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c := p[len(p)-6:]
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if c[0] == c[1] && c[2] == c[3] && c[4] == c[5] {
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p = p[:len(p)-6] + c[0:1] + c[2:3] + c[4:5]
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}
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}
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out = append(out, p)
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}
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return strings.Join(out, ";")
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}
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