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Diffstat (limited to 'examples/demos/src/main/scala/scrollmenu/ScrollMenu.scala')
| -rw-r--r-- | examples/demos/src/main/scala/scrollmenu/ScrollMenu.scala | 49 |
1 files changed, 49 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..9c0fbd2 --- /dev/null +++ b/examples/demos/src/main/scala/scrollmenu/ScrollMenu.scala @@ -0,0 +1,49 @@ +package scrollmenu + +import org.scalajs.dom + +case class Tree[T](value: T, children: Vector[Tree[T]]) + +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){ + scrolling = true + dom.requestAnimationFrame((d: Double) => start(threshold)) + } + def start(threshold: Double) = { + scrolling = 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 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) { + tree.children.foreach(_.value.frag.classList.remove("selected")) + } + menuItem.children(0).classList.add("pure-menu-selected") + }else{ + menuItem.children(0).classList.remove("pure-menu-selected") + menuItem.classList.add("hide") + menuItem.classList.remove("selected") + } + win + } + domTrees.map(walkTree) + } +}
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