text: import { runInOp } from "../display/operations.js"
  import { addToScrollTop } from "../display/scrolling.js"
  import { regLineChange } from "../display/view_tracking.js"
  import { heightAtLine, lineIsHidden } from "../line/spans.js"
  import { lineNo, updateLineHeight } from "../line/utils_line.js"
  import { widgetHeight } from "../measurement/widgets.js"
  import { eventMixin } from "../util/event.js"
  import { signalLater } from "../util/operation_group.js"
  
  import { changeLine } from "./changes.js"
  
  // Line widgets are block elements displayed above or below a line.
  
  export class LineWidget {
    constructor(doc, node, options) {
      if (options) for (let opt in options) if (options.hasOwnProperty(opt))
        this[opt] = options[opt]
      this.doc = doc
      this.node = node
    }
  
    clear() {
      let cm = this.doc.cm, ws = this.line.widgets, line = this.line, no = lineNo(line)
      if (no == null || !ws) return
      for (let i = 0; i < ws.length; ++i) if (ws[i] == this) ws.splice(i--, 1)
      if (!ws.length) line.widgets = null
      let height = widgetHeight(this)
      updateLineHeight(line, Math.max(0, line.height - height))
      if (cm) {
        runInOp(cm, () => {
          adjustScrollWhenAboveVisible(cm, line, -height)
          regLineChange(cm, no, "widget")
        })
        signalLater(cm, "lineWidgetCleared", cm, this, no)
      }
    }
  
    changed() {
      let oldH = this.height, cm = this.doc.cm, line = this.line
      this.height = null
      let diff = widgetHeight(this) - oldH
      if (!diff) return
      if (!lineIsHidden(this.doc, line)) updateLineHeight(line, line.height + diff)
      if (cm) {
        runInOp(cm, () => {
          cm.curOp.forceUpdate = true
          adjustScrollWhenAboveVisible(cm, line, diff)
          signalLater(cm, "lineWidgetChanged", cm, this, lineNo(line))
        })
      }
    }
  }
  eventMixin(LineWidget)
  
  function adjustScrollWhenAboveVisible(cm, line, diff) {
    if (heightAtLine(line) < ((cm.curOp && cm.curOp.scrollTop) || cm.doc.scrollTop))
      addToScrollTop(cm, diff)
  }
  
  export function addLineWidget(doc, handle, node, options) {
    let widget = new LineWidget(doc, node, options)
    let cm = doc.cm
    if (cm && widget.noHScroll) cm.display.alignWidgets = true
    changeLine(doc, handle, "widget", line => {
      let widgets = line.widgets || (line.widgets = [])
      if (widget.insertAt == null) widgets.push(widget)
      else widgets.splice(Math.min(widgets.length - 1, Math.max(0, widget.insertAt)), 0, widget)
      widget.line = line
      if (cm && !lineIsHidden(doc, line)) {
        let aboveVisible = heightAtLine(line) < doc.scrollTop
        updateLineHeight(line, line.height + widgetHeight(widget))
        if (aboveVisible) addToScrollTop(cm, widget.height)
        cm.curOp.forceUpdate = true
      }
      return true
    })
    if (cm) signalLater(cm, "lineWidgetAdded", cm, widget, typeof handle == "number" ? handle : lineNo(handle))
    return widget
  }
  