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package scrollmenu
import org.scalajs.dom
import scala.scalajs.js
import scalatags.JsDom.all._
case class Tree[T](value: T, children: Vector[Tree[T]])
case class MenuNode(frag: dom.HTMLElement, id: String, start: Int, end: Int)
/**
* High performance scrollspy to work keep the left menu bar in sync.
* Lots of sketchy imperative code in order to maximize performance.
*/
class ScrollSpy(structure: Tree[String],
main: dom.HTMLElement,
var clean: Boolean = false){
val (headers, domTrees) = {
var i = 0
def recurse(t: Tree[String], depth: Int): Tree[MenuNode] = {
val curr =
li(
a(
t.value,
href:="#"+Controller.munge(t.value),
cls:="menu-item"
)
)
val originalI = i
i += 1
val children = t.children.map(recurse(_, depth + 1))
Tree(
MenuNode(
curr(ul(paddingLeft := "15px",children.map(_.value.frag))).render,
Controller.munge(t.value),
originalI,
if (children.length > 0) children.map(_.value.end).max else originalI + 1
),
children
)
}
def offset(el: dom.HTMLElement, parent: dom.HTMLElement): Double = {
if (el == parent) 0
else el.offsetTop + offset(el.offsetParent.asInstanceOf[dom.HTMLElement], parent)
}
val headers = {
val menuItems = {
def rec(current: Tree[String]): Seq[String] = {
current.value +: current.children.flatMap(rec)
}
rec(structure).tail
}
menuItems.map(Controller.munge)
.map(dom.document.getElementById)
.map(offset(_, main))
.toVector
}
val domTrees = structure.children.map(recurse(_, 0))
(headers, domTrees)
}
private[this] var scrolling = false
def apply() = {
if (!scrolling) {
scrolling = true
dom.requestAnimationFrame((d: Double) => start())
}
}
private[this] var previousId = ""
private[this] def start() = {
scrolling = false
def scroll(el: dom.Element) = {
val rect = el.getBoundingClientRect()
if (rect.top <= 0)
el.scrollIntoView(true)
else if (rect.top > dom.innerHeight)
el.scrollIntoView(false)
}
def walkTree(tree: Tree[MenuNode]): Boolean = {
val Tree(MenuNode(menuItem, itemId, start, end), children) = tree
val before = headers(start) <= main.scrollTop
val after = (end >= headers.length) || headers(end) > main.scrollTop
val win = before && after
if (win){
menuItem.classList.remove("hide")
var winFound = false
for(c <- tree.children){
val newWinFound = walkTree(c)
if (!winFound) c.value.frag.classList.add("selected")
else c.value.frag.classList.remove("selected")
winFound = winFound | newWinFound
}
if (!winFound) {
if (previousId != itemId){
previousId = itemId
// This means it's the leaf element, because it won but there
// aren't any children which won, so it must be the actual leaf
tree.children.foreach(_.value.frag.classList.remove("selected"))
scroll(menuItem.children(0))
dom.history.replaceState(null, null, "#" + itemId)
}
}
menuItem.children(0).classList.add("pure-menu-selected")
}else{
if(clean) tree.children.map(walkTree)
menuItem.children(0).classList.remove("pure-menu-selected")
menuItem.classList.add("hide")
menuItem.classList.remove("selected")
}
win
}
domTrees.map(walkTree)
}
}
|
