From 37babbe3155021b1e2a6522f7b63c921917a53fe Mon Sep 17 00:00:00 2001
From: Josh Crowther <jshcrowthe@gmail.com>
Date: Sat, 10 Dec 2016 09:32:25 -0500
Subject: [PATCH 1/2] Add helper functions

---
 iron-list.html | 43 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 43 insertions(+)

diff --git a/iron-list.html b/iron-list.html
index 27b92725..b49f007b 100644
--- a/iron-list.html
+++ b/iron-list.html
@@ -1630,6 +1630,49 @@
         return;
       }
       this.toggleSelectionForItem(model[this.as]);
+    /**
+     * Updates the models of all physical items 
+     */
+    _updatePhysicalItemModels: function() {
+      this._physicalItems.map(function(el) {
+        return this.modelForElement(el);
+      }.bind(this)).forEach(function(model) {
+        model[this.selectedAs] = (this.$.selector).isSelected(this.items[model[this.indexAs]]);
+      }.bind(this));
+    },
+
+    /**
+     * UnSelect all items in a certain range (inclusive of both start and end)
+     */
+    _deselectRange: function(start, end) {
+      this.items.slice(start, end + 1)
+        .map(function(item) {
+          return this._getNormalizedItem(item);
+        }.bind(this))
+        .filter(function(item) {
+          return (this.$.selector).isSelected(item);
+        }.bind(this))
+        .forEach(function(item) {
+          this.$.selector.deselect(item);
+        }.bind(this));
+      this._updatePhysicalItemModels();
+    },
+
+    /**
+     * Select all items in a certain range (inclusive of both start and end)
+     */
+    _selectRange: function(start, end) {
+      this.items.slice(start, end + 1)
+        .map(function(item) {
+          return this._getNormalizedItem(item);
+        }.bind(this))
+        .filter(function(item) {
+          return !(this.$.selector).isSelected(item);
+        }.bind(this))
+        .forEach(function(item) {
+          this.$.selector.select(item);
+        }.bind(this));
+      this._updatePhysicalItemModels();
     },
 
     _multiSelectionChanged: function(multiSelection) {

From e739c9f85b92cdb770b9e7060169c97c5773b6c3 Mon Sep 17 00:00:00 2001
From: Josh Crowther <jshcrowthe@gmail.com>
Date: Sat, 10 Dec 2016 09:32:54 -0500
Subject: [PATCH 2/2] Add shift select handler function

---
 iron-list.html | 39 ++++++++++++++++++++++++++++++++++++++-
 1 file changed, 38 insertions(+), 1 deletion(-)

diff --git a/iron-list.html b/iron-list.html
index b49f007b..f36603f7 100644
--- a/iron-list.html
+++ b/iron-list.html
@@ -1629,7 +1629,44 @@
       if (activeEl && physicalItem !== activeEl && physicalItem.contains(activeEl) && activeElTabIndex !== SECRET_TABINDEX) {
         return;
       }
-      this.toggleSelectionForItem(model[this.as]);
+
+      var sourceEvent = e && e.detail && e.detail.sourceEvent;
+      
+      // Handle `shift` click scenario
+      if (this.multiSelection && this.selectedItems.length && sourceEvent.shiftKey) {
+        this._shiftSelectHandler(model[this.as]);
+      } else {
+        this.toggleSelectionForItem(model[this.as]);
+      }
+    },
+
+    _shiftSelectHandler: function(selectedItem) {
+      var selectedIndex = this.items.indexOf(selectedItem);
+      var _selectedItemIndexes = this.selectedItems.map(function(item) {
+        return this.items.indexOf(item);
+      }.bind(this));
+
+      var firstSelectedIndex = _selectedItemIndexes.reduce(function(currentIndex, itemIndex) {
+        return Math.min(currentIndex, itemIndex);
+      });
+
+      var lastSelectedIndex = _selectedItemIndexes.reduce(function(currentIndex, itemIndex) {
+        return Math.max(currentIndex, itemIndex);
+      });
+      
+      var startIndex = Math.min(selectedIndex, firstSelectedIndex);
+      var lastIndex = Math.max(selectedIndex, lastSelectedIndex);
+
+      // Select the range created with the shift select
+      this._selectRange(startIndex, lastIndex);
+
+      // Deselect everything outside of the shift select range (will only occur
+      // if a user shift selects in the middle of a range)
+      if (selectedIndex > firstSelectedIndex && selectedIndex < lastSelectedIndex) {
+        this._deselectRange(selectedIndex + 1, lastSelectedIndex);
+      }
+    },
+
     /**
      * Updates the models of all physical items 
      */