Make text walker a separate module

README.md

@@ -257,10 +257,28 @@ An overlayer object implements the following interface for the consumption of re
 - `.element`: the DOM element of the overlayer. This element will be inserted, resized, and positioned automatically by the renderer on top of the page.
 - `.redraw()`: called by the renderer when the overlay needs to be redrawn.
 
+### The Text Walker
+
+Not a particularly descriptive name, but essentially, `text-walker.js` is a small DOM utility that allows you to
+
+1. Gather all text nodes in a `Range`, `Document` or `DocumentFragment` into an array of strings.
+2. Perform splitting or matching on the strings.
+3. Get back the results of these string operations as `Range`s.
+
+E.g. you can join all the text nodes together, use `Intl.Segmenter` to segment the string into words, and get the results in DOM Ranges, so you can mark up those words in the original document.
+
+In foliate-js, this is used for searching and TTS.
+
 ### Searching
 
 It provides a search module, which can in fact be used as a standalone module for searching across any array of strings. There's no limit on the number of strings a match is allowed to span. It's based on `Intl.Collator` and `Intl.Segmenter`, to support ignoring diacritics and matching whole words only. It's extrenely slow, and you'd probably want to load results incrementally.
 
+### Text-to-Speech (TTS)
+
+The TTS module doesn't directly handle speech output. Rather, its methods return SSML documents (as strings), which you can then feed to your speech synthesizer.
+
+The SSML attributes `ssml:ph` and `ssml:alphabet` are supported. There's no support for PLS and CSS Speech.
+
 ### Supported Browsers
 
 The main use of the library is for use in [Foliate](https://github.com/johnfactotum/foliate), which uses WebKitGTK. As such it's the only engine that has been tested extensively. But it should also work in Chromium and Firefox.

text-walker.js

@@ -0,0 +1,43 @@
+const walkRange = (range, walker) => {
+    const nodes = []
+    for (let node = walker.currentNode; node; node = walker.nextNode()) {
+        const compare = range.comparePoint(node, 0)
+        if (compare === 0) nodes.push(node)
+        else if (compare > 0) break
+    }
+    return nodes
+}
+
+const walkDocument = (_, walker) => {
+    const nodes = []
+    for (let node = walker.nextNode(); node; node = walker.nextNode())
+        nodes.push(node)
+    return nodes
+}
+
+const filter = NodeFilter.SHOW_ELEMENT | NodeFilter.SHOW_TEXT
+    | NodeFilter.SHOW_CDATA_SECTION
+
+const acceptNode = node => {
+    if (node.nodeType === 1) {
+        const name = node.tagName.toLowerCase()
+        if (name === 'script' || name === 'style') return NodeFilter.FILTER_REJECT
+        return NodeFilter.FILTER_SKIP
+    }
+    return NodeFilter.FILTER_ACCEPT
+}
+
+export const textWalker = function* (x, func) {
+    const root = x.commonAncestorContainer ?? x.body ?? x
+    const walker = document.createTreeWalker(root, filter, { acceptNode })
+    const walk = x.commonAncestorContainer ? walkRange : walkDocument
+    const nodes = walk(x, walker)
+    const strs = nodes.map(node => node.nodeValue)
+    const makeRange = (startIndex, startOffset, endIndex, endOffset) => {
+        const range = document.createRange()
+        range.setStart(nodes[startIndex], startOffset)
+        range.setEnd(nodes[endIndex], endOffset)
+        return range
+    }
+    for (const match of func(strs, makeRange)) yield match
+}

tts.js

@@ -21,48 +21,6 @@ const getAlphabet = el => {
     return x ? x : el.parentElement ? getAlphabet(el.parentElement) : null
 }
 
-const getWalker = (getRoot, walk) => function* (x, func) {
-    const root = getRoot(x)
-    const filter = NodeFilter.SHOW_ELEMENT | NodeFilter.SHOW_TEXT
-        | NodeFilter.SHOW_CDATA_SECTION
-    const { FILTER_ACCEPT, FILTER_REJECT, FILTER_SKIP } = NodeFilter
-    const acceptNode = node => {
-        if (node.nodeType === 1) {
-            const name = node.tagName.toLowerCase()
-            if (name === 'script' || name === 'style') return FILTER_REJECT
-            return FILTER_SKIP
-        }
-        return FILTER_ACCEPT
-    }
-    const walker = document.createTreeWalker(root, filter, { acceptNode })
-    const nodes = walk(x, walker)
-    const strs = nodes.map(node => node.nodeValue)
-    const makeRange = (startIndex, startOffset, endIndex, endOffset) => {
-        const range = document.createRange()
-        range.setStart(nodes[startIndex], startOffset)
-        range.setEnd(nodes[endIndex], endOffset)
-        return range
-    }
-    for (const match of func(strs, makeRange)) yield match
-}
-
-const rangeWalker = getWalker(x => x.commonAncestorContainer, (range, walker) => {
-    const nodes = []
-    for (let node = walker.currentNode; node; node = walker.nextNode()) {
-        const compare = range.comparePoint(node, 0)
-        if (compare === 0) nodes.push(node)
-        else if (compare > 0) break
-    }
-    return nodes
-})
-
-const fragmentWalker = getWalker(x => x, (range, walker) => {
-    const nodes = []
-    for (let node = walker.nextNode(); node; node = walker.nextNode())
-        nodes.push(node)
-    return nodes
-})
-
 const getSegmenter = (lang = 'en', granularity = 'word') => {
     const segmenter = new Intl.Segmenter(lang, { granularity })
     const granularityIsWord = granularity === 'word'
@@ -138,7 +96,7 @@ const fragmentToSSML = (fragment, inherited) => {
     return ssml
 }
 
-const getFragmentWithMarks = (range, granularity) => {
+const getFragmentWithMarks = (range, textWalker, granularity) => {
     const lang = getLang(range.commonAncestorContainer)
     const alphabet = getAlphabet(range.commonAncestorContainer)
 
@@ -148,8 +106,8 @@ const getFragmentWithMarks = (range, granularity) => {
     // we need ranges on both the original document (for highlighting)
     // and the document fragment (for inserting marks)
     // so unfortunately need to do it twice, as you can't copy the ranges
-    const entries = [...rangeWalker(range, segmenter)]
-    const fragmentEntries = [...fragmentWalker(fragment, segmenter)]
+    const entries = [...textWalker(range, segmenter)]
+    const fragmentEntries = [...textWalker(fragment, segmenter)]
 
     for (const [name, range] of fragmentEntries) {
         const mark = document.createElement('foliate-mark')
@@ -249,11 +207,11 @@ export class TTS {
     #ranges
     #lastMark
     #serializer = new XMLSerializer()
-    constructor(doc, highlight) {
+    constructor(doc, textWalker, highlight) {
         this.doc = doc
         this.highlight = highlight
         this.#list = new ListIterator(getBlocks(doc), range => {
-            const { entries, ssml } = getFragmentWithMarks(range)
+            const { entries, ssml } = getFragmentWithMarks(range, textWalker)
             this.#ranges = new Map(entries)
             return [ssml, range]
         })

view.js

@@ -1,6 +1,7 @@
 import * as CFI from './epubcfi.js'
 import { TOCProgress, SectionProgress } from './progress.js'
 import { Overlayer } from './overlayer.js'
+import { textWalker } from './text-walker.js'
 
 const SEARCH_PREFIX = 'foliate-search:'
 
@@ -46,30 +47,6 @@ class History extends EventTarget {
     }
 }
 
-const textWalker = function* (doc, func) {
-    const filter = NodeFilter.SHOW_ELEMENT | NodeFilter.SHOW_TEXT
-        | NodeFilter.SHOW_CDATA_SECTION
-    const { FILTER_ACCEPT, FILTER_REJECT, FILTER_SKIP } = NodeFilter
-    const acceptNode = node => {
-        const name = node.localName?.toLowerCase()
-        if (name === 'script' || name === 'style') return FILTER_REJECT
-        if (node.nodeType === 1) return FILTER_SKIP
-        return FILTER_ACCEPT
-    }
-    const walker = doc.createTreeWalker(doc.body, filter, { acceptNode })
-    const nodes = []
-    for (let node = walker.nextNode(); node; node = walker.nextNode())
-        nodes.push(node)
-    const strs = nodes.map(node => node.nodeValue)
-    const makeRange = (startIndex, startOffset, endIndex, endOffset) => {
-        const range = doc.createRange()
-        range.setStart(nodes[startIndex], startOffset)
-        range.setEnd(nodes[endIndex], endOffset)
-        return range
-    }
-    for (const match of func(strs, makeRange)) yield match
-}
-
 const languageInfo = lang => {
     if (!lang) return {}
     try {
@@ -417,7 +394,7 @@ export class View extends HTMLElement {
         const doc = this.renderer.getContents()[0].doc
         if (this.tts && this.tts.doc === doc) return
         const { TTS } = await import('./tts.js')
-        this.tts = new TTS(doc, range =>
+        this.tts = new TTS(doc, textWalker, range =>
             this.renderer.scrollToAnchor(range, true))
     }
 }