WCartesianChart changes:

 - Continue drag even when updated while dragging
 - Changed equality check to closeness check for WTransform

src/Wt/WJavaScriptExposableObject

@@ -80,6 +80,8 @@ public:
    */
   std::string jsRef() const;
 
+  bool closeTo(const WJavaScriptExposableObject& other) const { return false; }
+
 protected:
   bool sameBindingAs(const WJavaScriptExposableObject &rhs) const;
   void assignBinding(const WJavaScriptExposableObject &rhs);

src/Wt/WJavaScriptHandle

@@ -111,7 +111,7 @@ public:
     WJavaScriptExposableObject::JSInfo *binding = value_->clientBinding_;
     value_->clientBinding_ = 0;
 
-    bool changed = *value_ != v;
+    bool changed = !value_->closeTo(v);
     (*value_) = v;
 
     value_->clientBinding_ = binding;

src/Wt/WTransform

@@ -361,6 +361,8 @@ public:
    */
   static const WTransform Identity;
 
+  bool closeTo(const WTransform& other) const;
+
   virtual std::string jsValue() const WT_CXX11ONLY(override) ;
 
 protected:

src/Wt/WTransform.C

@@ -586,4 +586,19 @@ void WTransform::assignFromJSON(const Json::Value &value)
   }
 }
 
+bool WTransform::closeTo(const WTransform &other) const
+{
+  if (isJavaScriptBound() || other.isJavaScriptBound())
+    return false;
+
+  static const double EPS = 1E-12;
+
+  return std::abs(m_[0] - other.m_[0]) <= EPS &&
+         std::abs(m_[1] - other.m_[1]) <= EPS &&
+         std::abs(m_[2] - other.m_[2]) <= EPS &&
+         std::abs(m_[3] - other.m_[3]) <= EPS &&
+         std::abs(m_[4] - other.m_[4]) <= EPS &&
+         std::abs(m_[5] - other.m_[5]) <= EPS;
+}
+
 }

src/js/WCartesianChart.js

@@ -728,8 +728,10 @@ WT_DECLARE_WT_MEMBER_BIG
     this.mouseDrag = function(o, event) {
       if (pointerActive)
         return;
-      if (dragPreviousXY === null)
+      if (dragPreviousXY === null) {
+        self.mouseDown(o, event);
         return;
+      }
       var c = WT.widgetCoordinates(target.canvas, event);
       if (WT.buttons === 1) {
         if (dragCurrentYAxis === -1 && !dragXAxis &&