From dbafdcf1ff2844f82ea9094e624d5f20a694ac58 Mon Sep 17 00:00:00 2001
From: Neil Fraser <fraser@google.com>
Date: Wed, 27 Mar 2019 15:24:39 -0700
Subject: [PATCH] Prevent gestures from being broken by zoom/scroll.

---
 core/workspace_svg.js | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/core/workspace_svg.js b/core/workspace_svg.js
index f4ed5eb46..d62f720f7 100644
--- a/core/workspace_svg.js
+++ b/core/workspace_svg.js
@@ -1304,19 +1304,18 @@ Blockly.WorkspaceSvg.prototype.isMovable = function() {
  * @private
  */
 Blockly.WorkspaceSvg.prototype.onMouseWheel_ = function(e) {
+  // Don't scroll or zoom anything if drag is in progress.
+  if (this.currentGesture_) {
+    e.preventDefault();
+    e.stopPropagation();
+    return;
+  }
   var canWheelZoom = this.options.zoomOptions && this.options.zoomOptions.wheel;
   var canWheelMove = this.options.moveOptions && this.options.moveOptions.wheel;
   if (!canWheelZoom && !canWheelMove) {
     return;
   }
 
-  // TODO: Remove gesture cancellation and compensate for coordinate skew during
-  // zoom.
-  if (this.currentGesture_) {
-    this.currentGesture_.cancel();
-  }
-
-
   var scrollDelta = Blockly.utils.getScrollDeltaPixels(e);
   if (canWheelZoom && (e.ctrlKey || !canWheelMove)) {
     // The vertical scroll distance that corresponds to a click of a zoom button.