Function syncScrollToView

public/js/lib/syncscroll.js:360–411

(event, preventAnimate)

let editScrollingTimer = null

export function syncScrollToView (event, preventAnimate) {
  if (appState.currentMode !== modeType.both || !appState.syncscroll || !viewArea) return
  if (window.preventSyncScrollToView) {
    if (typeof preventSyncScrollToView === 'number') {
      window.preventSyncScrollToView--
    } else {
      window.preventSyncScrollToView = false
    }
    return
  }
  if (!scrollMap || !lineHeightMap) {
    buildMap(() => {
      syncScrollToView(event, preventAnimate)
    })
    return
  }
  if (viewScrolling) return

  let posTo
  let topDiffPercent, posToNextDiff
  const scrollInfo = editor.getScrollInfo()
  const textHeight = editor.defaultTextHeight()
  const lineNo = Math.floor(scrollInfo.top / textHeight)
  // if reach the last line, will start lerp to the bottom
  const diffToBottom = (scrollInfo.top + scrollInfo.clientHeight) - (scrollInfo.height - textHeight)
  if (scrollInfo.height > scrollInfo.clientHeight && diffToBottom > 0) {
    topDiffPercent = diffToBottom / textHeight
    posTo = scrollMap[lineNo + 1]
    posToNextDiff = (viewBottom - posTo) * topDiffPercent
    posTo += Math.floor(posToNextDiff)
  } else {
    topDiffPercent = (scrollInfo.top % textHeight) / textHeight
    posTo = scrollMap[lineNo]
    posToNextDiff = (scrollMap[lineNo + 1] - posTo) * topDiffPercent
    posTo += Math.floor(posToNextDiff)
  }

  if (preventAnimate) {
    viewArea.scrollTop(posTo)
  } else {
    const posDiff = Math.abs(viewArea.scrollTop() - posTo)
    var duration = posDiff / 50
    duration = duration >= 100 ? duration : 100
    viewArea.stop(true, true).animate({
      scrollTop: posTo
    }, duration, 'linear')
  }

  editScrolling = true
  clearTimeout(editScrollingTimer)
  editScrollingTimer = setTimeout(editScrollingTimeoutInner, duration * 1.5)
}

function editScrollingTimeoutInner () {
  editScrolling = false