420 lines
11 KiB
Go
420 lines
11 KiB
Go
package textmeasure
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import (
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"bytes"
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"fmt"
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"math"
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"strings"
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"github.com/PuerkitoBio/goquery"
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"github.com/yuin/goldmark"
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goldmarkHtml "github.com/yuin/goldmark/renderer/html"
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"golang.org/x/net/html"
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"oss.terrastruct.com/util-go/go2"
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"oss.terrastruct.com/d2/d2renderers/d2fonts"
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)
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var markdownRenderer goldmark.Markdown
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// these are css values from github-markdown.css so we can accurately compute the rendered dimensions
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const (
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MarkdownFontSize = d2fonts.FONT_SIZE_M
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MarkdownLineHeight = 1.5
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MarkdownLineHeightPx = MarkdownFontSize * MarkdownLineHeight
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PaddingLeft_ul_ol = 32
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MarginBottom_ul = MarkdownFontSize
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MarginTop_li_p = MarkdownFontSize
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MarginBottom_p = MarkdownFontSize
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LineHeight_h = 1.25
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MarginTop_h = 24
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MarginBottom_h = 16
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PaddingBottom_h1_h2_em = 0.3
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BorderBottom_h1_h2 = 1
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Height_hr = 4
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MarginTopBottom_hr = 24
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Padding_pre = 16
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MarginBottom_pre = 16
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LineHeight_pre = 1.45
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FontSize_pre_code_em = 0.85
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PaddingTopBottom_code_em = 0.2
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PaddingLeftRight_code_em = 0.4
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PaddingLR_blockquote_em = 1.
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MarginBottom_blockquote = 16
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BorderLeft_blockquote_em = 0.25
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FONT_SIZE_H1 = d2fonts.FONT_SIZE_XXXL
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FONT_SIZE_H2 = d2fonts.FONT_SIZE_XL
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FONT_SIZE_H3 = d2fonts.FONT_SIZE_L
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FONT_SIZE_H4 = d2fonts.FONT_SIZE_M
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FONT_SIZE_H5 = d2fonts.FONT_SIZE_S
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FONT_SIZE_H6 = d2fonts.FONT_SIZE_XS
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)
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var HeaderToFontSize = map[string]int{
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"h1": FONT_SIZE_H1,
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"h2": FONT_SIZE_H2,
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"h3": FONT_SIZE_H3,
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"h4": FONT_SIZE_H4,
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"h5": FONT_SIZE_H5,
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"h6": FONT_SIZE_H6,
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}
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func RenderMarkdown(m string) (string, error) {
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var output bytes.Buffer
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if err := markdownRenderer.Convert([]byte(m), &output); err != nil {
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return "", err
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}
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return output.String(), nil
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}
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func init() {
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markdownRenderer = goldmark.New(
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goldmark.WithRendererOptions(
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goldmarkHtml.WithUnsafe(),
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goldmarkHtml.WithXHTML(),
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),
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)
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}
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func MeasureMarkdown(mdText string, ruler *Ruler, fontFamily *d2fonts.FontFamily) (width, height int, err error) {
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render, err := RenderMarkdown(mdText)
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if err != nil {
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return width, height, err
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}
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doc, err := goquery.NewDocumentFromReader(strings.NewReader(render))
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if err != nil {
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return width, height, err
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}
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{
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originalLineHeight := ruler.LineHeightFactor
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ruler.boundsWithDot = true
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ruler.LineHeightFactor = MarkdownLineHeight
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defer func() {
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ruler.LineHeightFactor = originalLineHeight
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ruler.boundsWithDot = false
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}()
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}
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// TODO consider setting a max width + (manual) text wrapping
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bodyNode := doc.Find("body").First().Nodes[0]
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bodyAttrs := ruler.measureNode(0, bodyNode, fontFamily, MarkdownFontSize, d2fonts.FONT_STYLE_REGULAR)
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return int(math.Ceil(bodyAttrs.width)), int(math.Ceil(bodyAttrs.height)), nil
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}
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func hasPrev(n *html.Node) bool {
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if n.PrevSibling == nil {
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return false
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}
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if strings.TrimSpace(n.PrevSibling.Data) == "" {
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return hasPrev(n.PrevSibling)
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}
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return true
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}
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func hasNext(n *html.Node) bool {
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if n.NextSibling == nil {
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return false
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}
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// skip over empty text nodes
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if strings.TrimSpace(n.NextSibling.Data) == "" {
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return hasNext(n.NextSibling)
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}
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return true
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}
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func getPrev(n *html.Node) *html.Node {
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if n == nil {
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return nil
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}
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if strings.TrimSpace(n.Data) == "" {
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if next := getNext(n.PrevSibling); next != nil {
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return next
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}
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}
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return n
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}
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func getNext(n *html.Node) *html.Node {
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if n == nil {
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return nil
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}
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if strings.TrimSpace(n.Data) == "" {
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if next := getNext(n.NextSibling); next != nil {
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return next
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}
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}
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return n
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}
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func isBlockElement(elType string) bool {
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switch elType {
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case "blockquote",
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"div",
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"h1", "h2", "h3", "h4", "h5", "h6",
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"hr",
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"li",
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"ol",
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"p",
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"pre",
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"ul":
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return true
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default:
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return false
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}
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}
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func hasAncestorElement(n *html.Node, elType string) bool {
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if n.Parent == nil {
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return false
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}
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if n.Parent.Type == html.ElementNode && n.Parent.Data == elType {
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return true
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}
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return hasAncestorElement(n.Parent, elType)
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}
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type blockAttrs struct {
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width, height, marginTop, marginBottom float64
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}
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func (b *blockAttrs) isNotEmpty() bool {
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return b != nil && *b != blockAttrs{}
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}
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// measures node dimensions to match rendering with styles in github-markdown.css
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func (ruler *Ruler) measureNode(depth int, n *html.Node, fontFamily *d2fonts.FontFamily, fontSize int, fontStyle d2fonts.FontStyle) blockAttrs {
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if fontFamily == nil {
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fontFamily = go2.Pointer(d2fonts.SourceSansPro)
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}
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font := fontFamily.Font(fontSize, fontStyle)
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var parentElementType string
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if n.Parent != nil && n.Parent.Type == html.ElementNode {
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parentElementType = n.Parent.Data
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}
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debugMeasure := false
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var depthStr string
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if debugMeasure {
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if depth == 0 {
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fmt.Println()
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}
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depthStr = "┌"
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for i := 0; i < depth; i++ {
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depthStr += "-"
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}
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}
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switch n.Type {
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case html.TextNode:
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if strings.TrimSpace(n.Data) == "" {
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return blockAttrs{}
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}
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str := n.Data
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isCode := parentElementType == "pre" || parentElementType == "code"
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spaceWidths := 0.
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if !isCode {
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spaceWidth := ruler.spaceWidth(font)
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// MeasurePrecise will not include leading or trailing whitespace, so we account for it here
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str = strings.ReplaceAll(str, "\n", " ")
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str = strings.ReplaceAll(str, "\t", " ")
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if strings.HasPrefix(str, " ") {
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// consecutive leading/trailing spaces end up rendered as a single space
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str = strings.TrimPrefix(str, " ")
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if hasPrev(n) {
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spaceWidths += spaceWidth
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}
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}
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if strings.HasSuffix(str, " ") {
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str = strings.TrimSuffix(str, " ")
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if hasNext(n) {
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spaceWidths += spaceWidth
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}
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}
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}
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if parentElementType == "pre" {
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originalLineHeight := ruler.LineHeightFactor
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ruler.LineHeightFactor = LineHeight_pre
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defer func() {
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ruler.LineHeightFactor = originalLineHeight
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}()
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}
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w, h := ruler.MeasurePrecise(font, str)
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if isCode {
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w *= FontSize_pre_code_em
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h *= FontSize_pre_code_em
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}
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if debugMeasure {
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fmt.Printf("%stext(%v,%v)\n", depthStr, w, h)
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}
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return blockAttrs{w + spaceWidths, h, 0, 0}
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case html.ElementNode:
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isCode := false
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switch n.Data {
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case "h1", "h2", "h3", "h4", "h5", "h6":
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fontSize = HeaderToFontSize[n.Data]
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fontStyle = d2fonts.FONT_STYLE_BOLD
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originalLineHeight := ruler.LineHeightFactor
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ruler.LineHeightFactor = LineHeight_h
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defer func() {
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ruler.LineHeightFactor = originalLineHeight
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}()
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case "em":
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fontStyle = d2fonts.FONT_STYLE_ITALIC
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case "b", "strong":
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fontStyle = d2fonts.FONT_STYLE_BOLD
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case "pre", "code":
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fontFamily = go2.Pointer(d2fonts.SourceCodePro)
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fontStyle = d2fonts.FONT_STYLE_REGULAR
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isCode = true
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}
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block := blockAttrs{}
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if n.FirstChild != nil {
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first := getNext(n.FirstChild)
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last := getPrev(n.LastChild)
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var blocks []blockAttrs
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var inlineBlock *blockAttrs
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// first create blocks from combined inline elements, then combine all blocks
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// inlineBlock will be non-nil while inline elements are being combined into a block
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endInlineBlock := func() {
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if !isCode && inlineBlock.height > 0 && inlineBlock.height < MarkdownLineHeightPx {
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inlineBlock.height = MarkdownLineHeightPx
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}
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blocks = append(blocks, *inlineBlock)
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inlineBlock = nil
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}
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for child := n.FirstChild; child != nil; child = child.NextSibling {
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childBlock := ruler.measureNode(depth+1, child, fontFamily, fontSize, fontStyle)
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if child.Type == html.ElementNode && isBlockElement(child.Data) {
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if inlineBlock != nil {
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endInlineBlock()
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}
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newBlock := &blockAttrs{}
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newBlock.width = childBlock.width
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newBlock.height = childBlock.height
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if child == first && n.Data == "blockquote" {
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newBlock.marginTop = 0.
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} else {
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newBlock.marginTop = childBlock.marginTop
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}
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if child == last && n.Data == "blockquote" {
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newBlock.marginBottom = 0.
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} else {
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newBlock.marginBottom = childBlock.marginBottom
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}
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blocks = append(blocks, *newBlock)
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} else if child.Type == html.ElementNode && child.Data == "br" {
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if inlineBlock != nil {
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endInlineBlock()
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}
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} else if childBlock.isNotEmpty() {
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if inlineBlock == nil {
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// start inline block with child
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inlineBlock = &childBlock
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} else {
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// stack inline element dimensions horizontally
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inlineBlock.width += childBlock.width
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inlineBlock.height = go2.Max(inlineBlock.height, childBlock.height)
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inlineBlock.marginTop = go2.Max(inlineBlock.marginTop, childBlock.marginTop)
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inlineBlock.marginBottom = go2.Max(inlineBlock.marginBottom, childBlock.marginBottom)
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}
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}
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}
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if inlineBlock != nil {
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endInlineBlock()
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}
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var prevMarginBottom float64
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for i, b := range blocks {
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if i == 0 {
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block.marginTop = go2.Max(block.marginTop, b.marginTop)
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} else {
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marginDiff := b.marginTop - prevMarginBottom
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if marginDiff > 0 {
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block.height += marginDiff
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}
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}
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if i == len(blocks)-1 {
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block.marginBottom = go2.Max(block.marginBottom, b.marginBottom)
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} else {
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block.height += b.marginBottom
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prevMarginBottom = b.marginBottom
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}
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block.height += b.height
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block.width = go2.Max(block.width, b.width)
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}
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}
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switch n.Data {
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case "blockquote":
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block.width += (2*PaddingLR_blockquote_em + BorderLeft_blockquote_em) * float64(fontSize)
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block.marginBottom = go2.Max(block.marginBottom, MarginBottom_blockquote)
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case "p":
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if parentElementType == "li" {
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block.marginTop = go2.Max(block.marginTop, MarginTop_li_p)
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}
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block.marginBottom = go2.Max(block.marginBottom, MarginBottom_p)
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case "h1", "h2", "h3", "h4", "h5", "h6":
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block.marginTop = go2.Max(block.marginTop, MarginTop_h)
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block.marginBottom = go2.Max(block.marginBottom, MarginBottom_h)
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switch n.Data {
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case "h1", "h2":
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block.height += PaddingBottom_h1_h2_em*float64(fontSize) + BorderBottom_h1_h2
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}
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case "li":
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block.width += PaddingLeft_ul_ol
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if hasPrev(n) {
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block.marginTop = go2.Max(block.marginTop, 4)
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}
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case "ol", "ul":
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if hasAncestorElement(n, "ul") || hasAncestorElement(n, "ol") {
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block.marginTop = 0
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block.marginBottom = 0
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} else {
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block.marginBottom = go2.Max(block.marginBottom, MarginBottom_ul)
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}
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case "pre":
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block.width += 2 * Padding_pre
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block.height += 2 * Padding_pre
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block.marginBottom = go2.Max(block.marginBottom, MarginBottom_pre)
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case "code":
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if parentElementType != "pre" {
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block.width += 2 * PaddingLeftRight_code_em * float64(fontSize)
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block.height += 2 * PaddingTopBottom_code_em * float64(fontSize)
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}
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case "hr":
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block.height += Height_hr
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block.marginTop = go2.Max(block.marginTop, MarginTopBottom_hr)
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block.marginBottom = go2.Max(block.marginBottom, MarginTopBottom_hr)
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}
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if block.height > 0 && block.height < MarkdownLineHeightPx {
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block.height = MarkdownLineHeightPx
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}
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if debugMeasure {
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fmt.Printf("%s%s(%v,%v) mt:%v mb:%v\n", depthStr, n.Data, block.width, block.height, block.marginTop, block.marginBottom)
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}
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return block
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}
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return blockAttrs{}
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}
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