Improve handling of links

- Remove special handling of footnotes
- Open all links by default
- Reader can return `true` to prevent default action
- Expose link handling as a method, which the reader can use to set up
  links outside renderers (e.g. in popup footnotes)

reader.js

@@ -1,7 +1,6 @@
 import { View, getPosition } from './view.js'
 import { createTOCView } from './ui/tree.js'
 import { createMenu } from './ui/menu.js'
-import { createPopover } from './ui/popover.js'
 
 const isZip = async file => {
     const arr = new Uint8Array(await file.slice(0, 4).arrayBuffer())
@@ -245,8 +244,6 @@ class Reader {
         switch (obj.type) {
             case 'loaded': this.#onLoaded(obj); break
             case 'relocated': this.#onRelocated(obj); break
-            case 'reference': this.#onReference(obj); break
-            case 'external-link': globalThis.open(obj.uri, '_blank'); break
         }
     }
     #handleKeydown(event) {
@@ -269,31 +266,6 @@ class Reader {
         slider.title = `${percent} · ${loc}`
         if (tocItem?.href) this.#tocView?.setCurrentHref?.(tocItem.href)
     }
-    #onReference(obj) {
-        const { content, element } = obj
-        const { point, dir } = getPosition(element)
-        const iframe = document.createElement('iframe')
-        iframe.sandbox = 'allow-same-origin'
-        iframe.srcdoc = content
-        iframe.onload = () => {
-            const doc = iframe.contentDocument
-            doc.documentElement.style.colorScheme = 'light dark'
-            doc.body.style.margin = '18px'
-        }
-        Object.assign(iframe.style, {
-            border: '0',
-            width: '100%',
-            height: '100%',
-        })
-        const { popover, arrow, overlay } = createPopover(300, 250, point, dir)
-        overlay.style.zIndex = 3
-        popover.style.zIndex = 3
-        arrow.style.zIndex = 3
-        popover.append(iframe)
-        document.body.append(overlay)
-        document.body.append(popover)
-        document.body.append(arrow)
-    }
 }
 
 const open = async file => {

ui/popover.js

@@ -1,63 +0,0 @@
-const clamp = (min, max, x) => Math.min(max, Math.max(min, x))
-
-const arrowHeight = 10
-const arrowWidth = 20
-const radius = 6
-
-const createSVGElement = tag =>
-    document.createElementNS('http://www.w3.org/2000/svg', tag)
-
-const createArrow = down => {
-    const h = arrowHeight + 1
-    const svg = createSVGElement('svg')
-    svg.setAttribute('aria-hidden', 'true')
-    svg.setAttribute('width', arrowWidth)
-    svg.setAttribute('height', arrowHeight)
-    const polygon = createSVGElement('polygon')
-    polygon.setAttribute('points', down
-        ? `0 ${h}, ${arrowWidth / 2} 0, ${arrowWidth} ${h}`
-        : `0 0, ${arrowWidth / 2} ${h}, ${arrowWidth} 0`)
-    svg.classList.add(down ? 'popover-arrow-down' : 'popover-arrow-up')
-    svg.append(polygon)
-    return svg
-}
-
-export const createPopover = (width, height, { x, y }, dir) => {
-    const down = dir === 'down'
-    const fullHeight = height + arrowHeight
-    const overlay = document.createElement('div')
-    Object.assign(overlay.style, {
-        position: 'absolute',
-        left: '0',
-        top: '0',
-        width: '100vw',
-        height: '100vh',
-    })
-    const arrow = createArrow(down)
-    const top = clamp(0, window.innerHeight - (down ? height : fullHeight),
-        down ? y + arrowHeight : y - fullHeight)
-    Object.assign(arrow.style, {
-        position: 'absolute',
-        left: `${clamp(radius, window.innerWidth - arrowWidth - radius,
-            x - arrowWidth / 2)}px`,
-        top: `${down ? top - arrowHeight : top + height}px`,
-    })
-    const popover = document.createElement('div')
-    popover.setAttribute('role', 'dialog')
-    popover.classList.add('popover')
-    Object.assign(popover.style, {
-        position: 'absolute',
-        boxSizing: 'border-box',
-        overflow: 'hidden',
-        left: `${clamp(0, window.innerWidth - width, x - width / 2)}px`,
-        top: `${top}px`,
-        width: `${width}px`,
-        height: `${height}px`,
-    })
-    overlay.addEventListener('click', () => {
-        overlay.parentNode.removeChild(overlay)
-        arrow.parentNode.removeChild(arrow)
-        popover.parentNode.removeChild(popover)
-    })
-    return { popover, arrow, overlay }
-}

view.js

@@ -66,15 +66,6 @@ export const getPosition = target => {
     return start.point.y > window.innerHeight - end.point.y ? start : end
 }
 
-// https://www.w3.org/TR/epub-ssv-11/
-const SSV = Object.fromEntries(Array.from(Object.entries({
-    isRef: ['annoref', 'biblioref', 'glossref', 'noteref'],
-    isLink: ['backlink'],
-    isNote: ['annotation', 'note', 'footnote', 'endnote', 'rearnote'],
-}), ([k, v]) => [k, el =>
-    el.getAttributeNS('http://www.idpf.org/2007/ops', 'type')
-        ?.split(/s/)?.some(t => v.includes(t))]))
-
 export class View {
     #sectionProgress
     #tocProgress
@@ -150,8 +141,12 @@ export class View {
         doc.documentElement.dir ||= this.isCJK ? '' : this.textDirection
 
         this.renderer.setStyle?.(this.#css)
+        this.handleLinks(doc, index, this.emit)
 
-        // set handlers for links
+        this.emit?.({ type: 'loaded', doc, index })
+    }
+    handleLinks(doc, index, emit) {
+        const { book } = this
         const section = book.sections[index]
         for (const a of doc.querySelectorAll('a[href]'))
             a.addEventListener('click', e => {
@@ -159,25 +154,13 @@ export class View {
                 const href = a.getAttribute('href')
                 const uri = section?.resolveHref?.(href) ?? href
                 if (book?.isExternal?.(uri))
-                    this.emit?.({ type: 'external-link', uri })
-                else if (SSV.isRef(a)) {
-                    const { index, anchor } = book.resolveHref(uri)
-                    Promise.resolve(book.sections[index].createDocument())
-                        .then(doc => [anchor(doc), doc.contentType])
-                        .then(([el, type]) =>
-                            [el?.innerHTML, type, SSV.isNote(el)])
-                        .then(([content, contentType, isNote]) => content
-                            ? this.emit?.({
-                                type: 'reference',
-                                href: isNote ? null : uri,
-                                content, contentType, element: a,
-                            }) : null)
+                    Promise.resolve(emit?.({ type: 'external-link', a, uri }))
+                        .then(x => x ? null : window.open(uri, '_blank'))
+                        .catch(e => console.error(e))
+                else Promise.resolve(emit?.({ type: 'link', a, uri }))
+                        .then(x => x ? null : this.goTo(uri))
                         .catch(e => console.error(e))
-                    return
-                } else this.goTo(uri)
             })
-
-        this.emit?.({ type: 'loaded', doc, index })
     }
     async addAnnotation(annotation, remove) {
         const { value } = annotation