Fix hover states on back/forward buttons

interface/resources/qml/hifi/tablet/TabletAddressDialog.qml

@@ -20,6 +20,8 @@ import "../toolbars"
 import "../../styles-uit" as HifiStyles
 import "../../controls-uit" as HifiControls
 
+// references HMD, AddressManager, AddressBarDialog from root context
+
 StackView {
     id: root;
     HifiConstants { id: hifi }
@@ -114,8 +116,14 @@ StackView {
             }
             ToolbarButton {
                 id: backArrow;
+                buttonState: addressBarDialog.backEnabled;
                 imageURL: "../../../images/backward.svg";
-                onClicked: addressBarDialog.loadBack();
+                buttonEnabled: addressBarDialog.backEnabled;
+                onClicked: {
+                    if (buttonEnabled) {
+                        addressBarDialog.loadBack();
+                    }
+                }
                 anchors {
                     left: homeButton.right
                     verticalCenter: parent.verticalCenter
@@ -123,8 +131,14 @@ StackView {
             }
             ToolbarButton {
                 id: forwardArrow;
+                buttonState: addressBarDialog.forwardEnabled;
                 imageURL: "../../../images/forward.svg";
-                onClicked: addressBarDialog.loadForward();
+                buttonEnabled: addressBarDialog.forwardEnabled;
+                onClicked: {
+                    if (buttonEnabled) {
+                        addressBarDialog.loadForward();
+                    }
+                }
                 anchors {
                     left: backArrow.right
                     verticalCenter: parent.verticalCenter

interface/resources/qml/hifi/toolbars/ToolbarButton.qml

@@ -3,6 +3,8 @@ import QtQuick.Controls 1.4
 
 StateImage {
     id: button
+
+    property bool buttonEnabled: true
     property bool isActive: false
     property bool isEntered: false
 
@@ -39,6 +41,7 @@ StateImage {
     }
 
     function updateState() {
+        if (buttonEnabled) {
             if (!button.isEntered && !button.isActive) {
                 buttonState = imageOffOut;
             } else if (!button.isEntered && button.isActive) {
@@ -48,21 +51,27 @@ StateImage {
             } else {
                 buttonState = imageOnIn;
             }
+        } else {
+            buttonState = 0;
+        }
     }
 
     onIsActiveChanged: updateState();
+    onButtonEnabledChanged: updateState();
 
     Timer {
         id: asyncClickSender
         interval: 10
         repeat: false
         running: false
-        onTriggered: button.clicked();
+        onTriggered: {
+            button.clicked();
+        }
     }
 
     MouseArea {
         id: mouseArea
-        hoverEnabled: true
+        hoverEnabled: buttonEnabled
         anchors.fill: parent
         onClicked: asyncClickSender.start();
         onEntered: {