updated NodeKeyframe class to QObject for easier signal/slot handling

While the keyframes themselves are relatively simple, their usage is quite
complex and using QObjects as their base will help a ton of UI and backend
functionality.

app/node/keyframe.cpp

@@ -25,7 +25,6 @@ NodeKeyframe::NodeKeyframe() :
   value_(0),
   type_(kLinear)
 {
-
 }
 
 NodeKeyframe::NodeKeyframe(const rational &time, const QVariant &value, const NodeKeyframe::Type &type) :
@@ -43,6 +42,7 @@ const rational &NodeKeyframe::time() const
 void NodeKeyframe::set_time(const rational &time)
 {
   time_ = time;
+  emit TimeChanged(time_);
 }
 
 const QVariant &NodeKeyframe::value() const
@@ -53,6 +53,7 @@ const QVariant &NodeKeyframe::value() const
 void NodeKeyframe::set_value(const QVariant &value)
 {
   value_ = value;
+  emit ValueChanged(value_);
 }
 
 const NodeKeyframe::Type &NodeKeyframe::type() const
@@ -63,4 +64,5 @@ const NodeKeyframe::Type &NodeKeyframe::type() const
 void NodeKeyframe::set_type(const NodeKeyframe::Type &type)
 {
   type_ = type;
+  emit TypeChanged(type_);
 }

app/node/keyframe.h

@@ -21,15 +21,20 @@
 #ifndef NODEKEYFRAME_H
 #define NODEKEYFRAME_H
 
+#include <memory>
 #include <QVariant>
 
 #include "common/rational.h"
 
+class NodeKeyframe;
+using NodeKeyframePtr = std::shared_ptr<NodeKeyframe>;
+
 /**
  * @brief A point of data to be used at a certain time and interpolated with other data
  */
-class NodeKeyframe
+class NodeKeyframe : public QObject
 {
+  Q_OBJECT
 public:
 
   /**
@@ -71,6 +76,22 @@ public:
   const Type& type() const;
   void set_type(const Type& type);
 
+signals:
+  /**
+   * @brief Signal emitted when this keyframe's time is changed
+   */
+  void TimeChanged(const rational& time);
+
+  /**
+   * @brief Signal emitted when this keyframe's value is changed
+   */
+  void ValueChanged(const QVariant& value);
+
+  /**
+   * @brief Signal emitted when this keyframe's value is changed
+   */
+  void TypeChanged(const Type& type);
+
 private:
   rational time_;