finally added limits to bezier so curves can't loop over themselves

app/node/keyframe.cpp

@@ -30,10 +30,12 @@ NodeKeyframe::NodeKeyframe(const rational &time, const QVariant &value, const No
   time_(time),
   value_(value),
   type_(type),
-  bezier_control_in_(QPointF(-1.0, 0.0)),
-  bezier_control_out_(QPointF(1.0, 0.0)),
+  bezier_control_in_(QPointF(0.0, 0.0)),
+  bezier_control_out_(QPointF(0.0, 0.0)),
   track_(track),
-  element_(element)
+  element_(element),
+  previous_(nullptr),
+  next_(nullptr)
 {
   setParent(parent);
 }
@@ -85,8 +87,31 @@ const NodeKeyframe::Type &NodeKeyframe::type() const
 
 void NodeKeyframe::set_type(const NodeKeyframe::Type &type)
 {
-  type_ = type;
-  emit TypeChanged(type_);
+  if (type_ != type) {
+    type_ = type;
+
+    if (type_ == kBezier) {
+      // Set some sane defaults if this keyframe existed in the track and was just changed
+      if (bezier_control_in_.isNull()) {
+        if (previous_) {
+          // Set the in point to be half way between
+          set_bezier_control_in(QPointF((previous_->time().toDouble() - this->time().toDouble()) * 0.5, 0.0));
+        } else {
+          set_bezier_control_in(QPointF(-1.0, 0.0));
+        }
+      }
+
+      if (bezier_control_out_.isNull()) {
+        if (next_) {
+          set_bezier_control_out(QPointF((next_->time().toDouble() - this->time().toDouble()) * 0.5, 0.0));
+        } else {
+          set_bezier_control_out(QPointF(1.0, 0.0));
+        }
+      }
+    }
+
+    emit TypeChanged(type_);
+  }
 }
 
 const QPointF &NodeKeyframe::bezier_control_in() const
@@ -111,6 +136,32 @@ void NodeKeyframe::set_bezier_control_out(const QPointF &control)
   emit BezierControlOutChanged(bezier_control_out_);
 }
 
+QPointF NodeKeyframe::valid_bezier_control_in() const
+{
+  double t = time().toDouble();
+  qreal adjusted_x = t + bezier_control_in_.x();
+
+  if (previous_) {
+    // Limit to the point of that keyframe
+    adjusted_x = qMax(adjusted_x, previous_->time().toDouble());
+  }
+
+  return QPointF(adjusted_x - t, bezier_control_in_.y());
+}
+
+QPointF NodeKeyframe::valid_bezier_control_out() const
+{
+  double t = time().toDouble();
+  qreal adjusted_x = t + bezier_control_out_.x();
+
+  if (next_) {
+    // Limit to the point of that keyframe
+    adjusted_x = qMin(adjusted_x, next_->time().toDouble());
+  }
+
+  return QPointF(adjusted_x - t, bezier_control_out_.y());
+}
+
 const QPointF &NodeKeyframe::bezier_control(NodeKeyframe::BezierType type) const
 {
   if (type == kInHandle) {