From 5af8a2c8c422e37b8bd0dbfe6bde20bb4b703164 Mon Sep 17 00:00:00 2001
From: Rachel Fenichel <fenichel@google.com>
Date: Fri, 4 Mar 2016 14:52:37 -0800
Subject: [PATCH] snap to start of preexisting stack.

---
 core/block_svg.js | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/core/block_svg.js b/core/block_svg.js
index dfd4d6e0b1..e34d7e2914 100644
--- a/core/block_svg.js
+++ b/core/block_svg.js
@@ -437,6 +437,12 @@ Blockly.BlockSvg.prototype.onMouseUp_ = function(e) {
   }
   Blockly.terminateDrag_();
   if (Blockly.selected && Blockly.highlightedConnection_) {
+    if (Blockly.localConnection_ == Blockly.selected.nextConnection) {
+      // Snap to match the position of the pre-existing stack.
+      Blockly.selected.moveBy(
+          Blockly.highlightedConnection_.x_ - Blockly.localConnection_.x_,
+          Blockly.highlightedConnection_.y_ - Blockly.localConnection_.y_);
+    }
     // Connect two blocks together.
     Blockly.localConnection_.connect(Blockly.highlightedConnection_);
     if (this.rendered) {