git ssb

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const nest = require('depnest')
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const { h } = require('mutant')
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exports.gives = nest('app.html.scroller')
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exports.create = function (api) {
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  return nest('app.html.scroller', Scroller)
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  function Scroller ({ prepend = [], content = null, append = [] } = {}) {
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    content = content || h('section.content')
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    const container = h('Scroller', { style: { overflow: 'auto' } }, [
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      h('div.wrapper', [
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        h('header', prepend),
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        content,
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        h('footer', append)
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      ])
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    ])
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    container.scroll = keyscroll(content)
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    return {
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      content,
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      container
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    }
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  }
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}
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function keyscroll (container) {
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  var curMsgEl
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  if (!container) return () => {}
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  container.addEventListener('click', onActivateChild, false)
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  container.addEventListener('focus', onActivateChild, true)
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  function onActivateChild (ev) {
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    for (var el = ev.target; el; el = el.parentNode) {
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      if (el.parentNode === container) {
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        curMsgEl = el
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        return
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      }
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    }
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  }
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  return function scroll (d) {
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    selectChild((!curMsgEl || d === 'first') ? container.firstChild
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      : d < 0 ? curMsgEl.previousElementSibling || container.firstChild
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      : d > 0 ? curMsgEl.nextElementSibling || container.lastChild
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      : curMsgEl)
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    return curMsgEl
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  }
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  function selectChild (el) {
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    if (!el) { return }
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    if (!el.scrollIntoViewIfNeeded && !el.scrollIntoView) return
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    ;(el.scrollIntoViewIfNeeded || el.scrollIntoView).call(el)
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    el.focus()
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    curMsgEl = el
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  }
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}
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