Splice-Based Line Updates

splice-updates.coffee

  updateTileLines: (lines, tileStartRow, change) ->
    tileSize = @getTileSize()
    tileEndRow = tileStartRow + tileSize
    changeStart = change.start

    # Make change end-row exclusive to simplify logic below
    changeOldEnd = change.end + 1
    changeNewEnd = change.end + change.screenDelta + 1

    # If the change starts past this tile, stop now
    return lines if changeStart >= tileEndRow

    if changeOldEnd < tileStartRow or changeNewEnd < tileStartRow
      changeTranslation = tileStartRow - Math.min(changeOldEnd, changeNewEnd)
      changeOldEnd += changeTranslation
      changeNewEnd += changeTranslation

    changeStart = Math.max(tileStartRow, changeStart)
    changeOldEnd = Math.min(tileEndRow, changeOldEnd)
    changeNewEnd = Math.min(tileEndRow, changeNewEnd)

    console.log "splice"
    if changeNewEnd > changeStart
      newLines = @editor.linesForScreenRows(changeStart, changeNewEnd - 1)
      lines = lines.splice(changeStart - tileStartRow, changeOldEnd - changeStart, newLines...)
    else
      lines = lines.splice(changeStart - tileStartRow, changeOldEnd - changeStart)

    if lines.length > tileSize
      console.log "splice"
      lines = lines.splice(tileSize, lines.length - tileSize)

    if lines.length < tileSize
      console.log "splice"
      lines = lines.splice(lines.length, 0, @editor.linesForScreenRows(tileStartRow + lines.length, tileEndRow - 1)...)

    lines