feat(sidenav): track sidenav vissibilty and enter / leave backdrop if needed.

- Revert scope value if sidenav is shown.
- Throttle Resize Events

Fixes angular#4595

Author: devversion

src/components/sidenav/sidenav.js

@@ -208,7 +208,7 @@ function SidenavFocusDirective() {
  *   - `<md-sidenav md-is-locked-open="$mdMedia('min-width: 1000px')"></md-sidenav>`
  *   - `<md-sidenav md-is-locked-open="$mdMedia('sm')"></md-sidenav>` (locks open on small screens)
  */
-function SidenavDirective($mdMedia, $mdUtil, $mdConstant, $mdTheming, $animate, $compile, $parse, $log, $q, $document) {
+function SidenavDirective($mdMedia, $mdUtil, $mdConstant, $mdTheming, $animate, $compile, $parse, $log, $q, $document, $$rAF) {
   return {
     restrict: 'E',
     scope: {
@@ -229,6 +229,9 @@ function SidenavDirective($mdMedia, $mdUtil, $mdConstant, $mdTheming, $animate,
     var lastParentOverFlow;
     var triggeringElement = null;
     var promise = $q.when(true);
+    var skipSidenav = false;
+    var skipNextUpdate = false;
+    var $window = angular.element(window);
 
     var isLockedOpenParsed = $parse(attr.mdIsLockedOpen);
     var isLocked = function() {
@@ -244,22 +247,55 @@ function SidenavDirective($mdMedia, $mdUtil, $mdConstant, $mdTheming, $animate,
 
     $mdTheming.inherit(backdrop, element);
 
+    var throttleResize = $$rAF.throttle(revalidateVisibility);
+    $window.on('resize', throttleResize);
+    revalidateVisibility();
+
     element.on('$destroy', function() {
       backdrop.remove();
       sidenavCtrl.destroy();
+      $window.off('resize', throttleResize);
     });
 
     scope.$on('$destroy', function(){
+      $window.off('resize', throttleResize);
       backdrop.remove()
     });
 
     scope.$watch(isLocked, updateIsLocked);
     scope.$watch('isOpen', updateIsOpen);
 
 
+
     // Publish special accessor for the Controller instance
     sidenavCtrl.$toggleOpen = toggleOpen;
 
+    function revalidateVisibility() {
+      var lastValue = scope.isOpen;
+      if (attr.mdIsLockedOpen) return;
+
+      if (isHidden(element, true) && scope.isOpen) {
+        scope.isOpen = false;
+      } else if (!isHidden(element, true) && !scope.isOpen) {
+        scope.isOpen = true;
+      }
+
+      // If the revalidated isOpen Value got changed,
+      // we should apply it to the view without running the updateOpen watcher
+      if (lastValue != scope.isOpen) {
+        skipSidenav = true;
+        if (!scope.$$phase) scope.$apply();
+        skipSidenav = false;
+      }
+    }
+
+    // Check if the element is hidden by any hide attribute (using computed style)
+    function isHidden(element, compute) {
+      if (element[0].offsetParent == null) return true;
+      if (!compute) return false;
+      return window.getComputedStyle(element[0]).display === 'none';
+    }
+
     /**
      * Toggle the DOM classes to indicate `locked`
      * @param isLocked
@@ -278,26 +314,43 @@ function SidenavDirective($mdMedia, $mdUtil, $mdConstant, $mdTheming, $animate,
      * Toggle the SideNav view and attach/detach listeners
      * @param isOpen
      */
-    function updateIsOpen(isOpen) {
+    function updateIsOpen(isOpen, oldValue) {
+      if (skipNextUpdate) {
+        skipNextUpdate = false;
+        return;
+      }
+
       // Support deprecated md-sidenav-focus attribute as fallback
       var focusEl = $mdUtil.findFocusTarget(element) || $mdUtil.findFocusTarget(element,'[md-sidenav-focus]') || element;
       var parent = element.parent();
 
+      // little hack to check show abbility
+      if (!skipSidenav) {
+        var wasClosed = element.hasClass('md-closed');
+        element.removeClass('md-closed');
+        if (isHidden(element, false) && !skipSidenav) {
+          element.toggleClass('md-closed', wasClosed);
+          skipNextUpdate = true;
+          scope.isOpen = oldValue;
+          return;
+        }
+        element.toggleClass('md-closed', wasClosed);
+      }
+
       parent[isOpen ? 'on' : 'off']('keydown', onKeyDown);
       backdrop[isOpen ? 'on' : 'off']('click', close);
 
-      if ( isOpen ) {
+      if ( isOpen && !skipSidenav) {
         // Capture upon opening..
         triggeringElement = $document[0].activeElement;
       }
 
       disableParentScroll(isOpen);
 
-      return promise = $q.all([
-                isOpen ? $animate.enter(backdrop, parent) : $animate.leave(backdrop),
-                $animate[isOpen ? 'removeClass' : 'addClass'](element, 'md-closed')
-              ])
-              .then(function() {
+      var actions = [isOpen ? $animate.enter(backdrop, parent) : $animate.leave(backdrop)];
+      if (!skipSidenav) actions.push(isOpen ? $animate.removeClass(element, 'md-closed') : $animate.addClass(element, 'md-closed'));
+
+      return promise = $q.all(actions).then(function() {
                 // Perform focus when animations are ALL done...
                 if (scope.isOpen) {
                   focusEl && focusEl.focus();