1 files changed, 117 insertions, 0 deletions
diff --git a/examples/demos/src/main/scala/scrollmenu/ScrollMenu.scala b/examples/demos/src/main/scala/scrollmenu/ScrollMenu.scala
new file mode 100644
index 0000000..9ce9a2b
--- /dev/null
+++ b/examples/demos/src/main/scala/scrollmenu/ScrollMenu.scala
@@ -0,0 +1,117 @@
+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 = -1
+  def apply() = {
+    dom.clearTimeout(scrolling)
+    scrolling = dom.setTimeout(() => start(), 200)
+  }
+  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) {
+          // 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"))
+          if (dom.location.hash != itemId)
+            dom.history.pushState(null, null, "#"+itemId)
+          scroll(menuItem.children(0))
+
+        }
+        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)
+  }
+
+
+}
+\ No newline at end of file