From 4d22442e1b30b26464171688e296f61abf1b1066 Mon Sep 17 00:00:00 2001
From: "Evan W. Patton" <ewpatton@mit.edu>
Date: Tue, 23 May 2017 13:21:51 -0400
Subject: [PATCH] Add method for changing scrollbar visibility

---
 core/flyout.js        | 12 +++++++++---
 core/workspace_svg.js |  9 +++++++++
 2 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/core/flyout.js b/core/flyout.js
index 54e0fe8ca..adb005934 100644
--- a/core/flyout.js
+++ b/core/flyout.js
@@ -711,7 +711,9 @@ Blockly.Flyout.prototype.updateDisplay_ = function() {
   this.svgGroup_.style.display = show ? 'block' : 'none';
   // Update the scrollbar's visiblity too since it should mimic the
   // flyout's visibility.
-  this.scrollbar_.setContainerVisible(show);
+  if (this.scrollbar_) {
+    this.scrollbar_.setContainerVisible(show);
+  }
 };
 
 /**
@@ -721,7 +723,9 @@ Blockly.Flyout.prototype.hide = function() {
   if (!this.isVisible()) {
     return;
   }
-  Blockly.mainWorkspace.scrollbar.setContainerVisible(true);
+  if (Blockly.mainWorkspace) {
+    Blockly.mainWorkspace.setScrollbarsVisible(true);
+  }
   this.setVisible(false);
   // Delete all the event listeners.
   for (var x = 0, listen; listen = this.listeners_[x]; x++) {
@@ -742,7 +746,9 @@ Blockly.Flyout.prototype.hide = function() {
  *     Variables and procedures have a custom set of blocks.
  */
 Blockly.Flyout.prototype.show = function(xmlList) {
-  Blockly.mainWorkspace.scrollbar.setContainerVisible(false);  // hide parent's scrollbars
+  if (Blockly.mainWorkspace) {
+    Blockly.mainWorkspace.setScrollbarsVisible(false);  // hide parent's scrollbars
+  }
   this.workspace_.setResizesEnabled(false);
   this.hide();
   this.clearOldBlocks_();
diff --git a/core/workspace_svg.js b/core/workspace_svg.js
index d1d850a7c..96cb15128 100644
--- a/core/workspace_svg.js
+++ b/core/workspace_svg.js
@@ -1671,6 +1671,15 @@ Blockly.WorkspaceSvg.prototype.getButtonCallback = function(key) {
   return this.flyoutButtonCallbacks_[key];
 };
 
+/**
+ * Convenience method to hide the scrollbars on the workspace. This method has
+ * no effect if the workspace's options had scrollbars set to false.
+ * @param {boolean} visible true to show the scrollbars, otherwise false.
+ */
+Blockly.WorkspaceSvg.prototype.setScrollbarsVisible = function(visible) {
+  this.scrollbar && this.scrollbar.setContainerVisible(visible)
+};
+
 // Export symbols that would otherwise be renamed by Closure compiler.
 Blockly.WorkspaceSvg.prototype['setVisible'] =
     Blockly.WorkspaceSvg.prototype.setVisible;