Issue 2194 - Don't drag "Block Element" dialog when clicking into the text field

block.js

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-2015 Eyeo GmbH
  *
  * Adblock Plus is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 3 as
  * published by the Free Software Foundation.
  *
  * Adblock Plus is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 83 matching lines @@
   );
 }
 
 var dragStartX;
 var dragStartY;
 var dragEndX = null;
 var dragEndY = null;
 
 function onDragStart(event)
 {
-  dragStartX = event.screenX;
-  dragStartY = event.screenY;
+  var element = document.elementFromPoint(event.clientX, event.clientY);
+  if (element && element.localName == "textarea")
+  {
+    // Don't drag the dialog when the user has clicked into the textarea.
+    // Most likely the user just wants to focus it or select text there.
+    event.preventDefault();
+  }
+  else
+  {
+    dragStartX = event.screenX;
+    dragStartY = event.screenY;
+  }
 }
 
 function onDragEnd(event)
 {
   if (dragEndX == null)
     dragEndX = event.screenX;
   if (dragEndY == null)
     dragEndY = event.screenY;
 
   ext.backgroundPage.sendMessage({
@@ skipping 17 matching lines @@
 // However on Chrome, the coordinates in the drag event are unreliable.
 // So we need to get the coordinates from dragend event there.
 if (navigator.userAgent.indexOf(" Version/") != -1)
 {
   window.addEventListener("drag", function(event)
   {
     dragEndX = event.screenX;
     dragEndY = event.screenY;
   }, false);
 }