From 9e1ceb13eae9d323b9f0496f1be55eccae262e25 Mon Sep 17 00:00:00 2001
From: Tom Byers <tombaromba@gmail.com>
Date: Thu, 1 Nov 2018 20:33:00 +0000
Subject: [PATCH] Make local copy of stick-at-top JS

---
 .../stick-at-top-when-scrolling.js            | 128 ++++++++++++++++++
 gulpfile.babel.js                             |   2 +-
 2 files changed, 129 insertions(+), 1 deletion(-)
 create mode 100644 app/assets/javascripts/stick-at-top-when-scrolling.js

diff --git a/app/assets/javascripts/stick-at-top-when-scrolling.js b/app/assets/javascripts/stick-at-top-when-scrolling.js
new file mode 100644
index 000000000..9cb9421f8
--- /dev/null
+++ b/app/assets/javascripts/stick-at-top-when-scrolling.js
@@ -0,0 +1,128 @@
+;(function (global) {
+  'use strict'
+
+  var $ = global.jQuery
+  var GOVUK = global.GOVUK || {}
+
+  // Stick elements to top of screen when you scroll past, documentation is in the README.md
+  var sticky = {
+    _hasScrolled: false,
+    _scrollTimeout: false,
+    _hasResized: false,
+    _resizeTimeout: false,
+
+    getWindowDimensions: function () {
+      return {
+        height: $(global).height(),
+        width: $(global).width()
+      }
+    },
+    getWindowPositions: function () {
+      return {
+        scrollTop: $(global).scrollTop()
+      }
+    },
+    getElementOffset: function ($el) {
+      return $el.offset()
+    },
+    init: function () {
+      var $els = $('.js-stick-at-top-when-scrolling')
+
+      if ($els.length > 0) {
+        sticky.$els = $els
+
+        if (sticky._scrollTimeout === false) {
+          $(global).scroll(sticky.onScroll)
+          sticky._scrollTimeout = global.setInterval(sticky.checkScroll, 50)
+        }
+
+        if (sticky._resizeTimeout === false) {
+          $(global).resize(sticky.onResize)
+          sticky._resizeTimeout = global.setInterval(sticky.checkResize, 50)
+        }
+      }
+      if (GOVUK.stopScrollingAtFooter) {
+        $els.each(function (i, el) {
+          var $img = $(el).find('img')
+          if ($img.length > 0) {
+            var image = new global.Image()
+            image.onload = function () {
+              GOVUK.stopScrollingAtFooter.addEl($(el), $(el).outerHeight())
+            }
+            image.src = $img.attr('src')
+          } else {
+            GOVUK.stopScrollingAtFooter.addEl($(el), $(el).outerHeight())
+          }
+        })
+      }
+    },
+    onScroll: function () {
+      sticky._hasScrolled = true
+    },
+    onResize: function () {
+      sticky._hasResized = true
+    },
+    checkScroll: function () {
+      if (sticky._hasScrolled === true) {
+        sticky._hasScrolled = false
+
+        var windowVerticalPosition = sticky.getWindowPositions().scrollTop
+
+        var windowDimensions = sticky.getWindowDimensions()
+
+        sticky.$els.each(function (i, el) {
+          var $el = $(el)
+          var scrolledFrom = $el.data('scrolled-from')
+
+          if (scrolledFrom && windowVerticalPosition < scrolledFrom) {
+            sticky.release($el)
+          } else if (windowDimensions.width > 768 && windowVerticalPosition >= sticky.getElementOffset($el).top) {
+            sticky.stick($el)
+          }
+        })
+      }
+    },
+    checkResize: function () {
+      if (sticky._hasResized === true) {
+        sticky._hasResized = false
+
+        var windowDimensions = sticky.getWindowDimensions()
+
+        sticky.$els.each(function (i, el) {
+          var $el = $(el)
+
+          var elResize = $el.hasClass('js-sticky-resize')
+          if (elResize) {
+            var $shim = $('.shim')
+            var $elParent = $el.parent('div')
+            var elParentWidth = $elParent.width()
+            $shim.css('width', elParentWidth)
+            $el.css('width', elParentWidth)
+          }
+
+          if (windowDimensions.width <= 768) {
+            sticky.release($el)
+          }
+        })
+      }
+    },
+    stick: function ($el) {
+      if (!$el.hasClass('content-fixed')) {
+        $el.data('scrolled-from', sticky.getElementOffset($el).top)
+        var height = Math.max($el.height(), 1)
+        var width = $el.width()
+        $el.before('<div class="shim" style="width: ' + width + 'px; height: ' + height + 'px">&nbsp;</div>')
+        $el.css('width', width + 'px').addClass('content-fixed')
+      }
+    },
+    release: function ($el) {
+      if ($el.hasClass('content-fixed')) {
+        $el.data('scrolled-from', false)
+        $el.removeClass('content-fixed').css('width', '')
+        $el.siblings('.shim').remove()
+      }
+    }
+  }
+  GOVUK.stickAtTopWhenScrolling = sticky
+  global.GOVUK = GOVUK
+})(window)
diff --git a/gulpfile.babel.js b/gulpfile.babel.js
index a7da1e92e..1bd4b0a6f 100644
--- a/gulpfile.babel.js
+++ b/gulpfile.babel.js
@@ -60,7 +60,7 @@ gulp.task('javascripts', () => gulp
     paths.toolkit + 'javascripts/govuk/modules.js',
     paths.toolkit + 'javascripts/govuk/show-hide-content.js',
     paths.toolkit + 'javascripts/govuk/stop-scrolling-at-footer.js',
-    paths.toolkit + 'javascripts/govuk/stick-at-top-when-scrolling.js',
+    paths.src + 'javascripts/stick-at-top-when-scrolling.js',
     paths.src + 'javascripts/detailsPolyfill.js',
     paths.src + 'javascripts/apiKey.js',
     paths.src + 'javascripts/autofocus.js',