1 files changed, 66 insertions, 8 deletions

diff --git a/examples/demos/src/main/scala/scrollmenu/ScrollMenu.scala b/examples/demos/src/main/scala/scrollmenu/ScrollMenu.scala
index 9c0fbd2..7b238f4 100644
--- a/examples/demos/src/main/scala/scrollmenu/ScrollMenu.scala
+++ b/examples/demos/src/main/scala/scrollmenu/ScrollMenu.scala
@@ -2,6 +2,8 @@ package scrollmenu
 
 import org.scalajs.dom
 
+import scalatags.JsDom.all._
+
 case class Tree[T](value: T, children: Vector[Tree[T]])
 
 case class MenuNode(frag: dom.HTMLElement, start: Int, end: Int)
@@ -10,18 +12,69 @@ case class MenuNode(frag: dom.HTMLElement, 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(headers: Vector[Double], domTrees: Seq[Tree[MenuNode]]){
-  var scrolling = false
-  def apply(threshold: Double) = if (!scrolling){
+class ScrollSpy(structure: Tree[String], main: dom.HTMLElement){
+  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,
+          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(threshold: => Double) = if (!scrolling){
     scrolling = true
-    dom.requestAnimationFrame((d: Double) => start(threshold))
+    dom.setTimeout(() => start(threshold), 200)
   }
-  def start(threshold: Double) = {
+  private[this] def start(threshold: Double) = {
     scrolling = false
+    def scroll(el: dom.HTMLElement) = {
+      val rect = el.getBoundingClientRect()
+      if (rect.top <= 0)
+        el.scrollIntoView(true)
+      else if (rect.bottom > dom.innerHeight)
+        el.scrollIntoView(false)
+    }
     def walkTree(tree: Tree[MenuNode]): Boolean = {
-      val Tree(MenuNode(menuItem, index, next), children) = tree
-      val before = headers(index) < threshold
-      val after = (next >= headers.length) || headers(next) > threshold
+      val Tree(MenuNode(menuItem, start, end), children) = tree
+      val before = headers(start) < threshold
+      val after = (end >= headers.length) || headers(end) > threshold
       val win = before && after
       if (win){
         menuItem.classList.remove("hide")
@@ -34,7 +87,10 @@ class ScrollSpy(headers: Vector[Double], domTrees: Seq[Tree[MenuNode]]){
           winFound = winFound | newWinFound
         }
         if (!winFound) {
+          // 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)
         }
         menuItem.children(0).classList.add("pure-menu-selected")
       }else{
@@ -46,4 +102,6 @@ class ScrollSpy(headers: Vector[Double], domTrees: Seq[Tree[MenuNode]]){
     }
     domTrees.map(walkTree)
   }
+
+
 }
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