curve/timeline: improved user interface behavior

* Implements "auto-fit" setting for curve view and sets it on open.
* Improves scroll zooming on all TimelineViewBase derivatives.
* Improves code sharing for better maintenance.

app/widget/keyframeview/keyframeviewbase.cpp

@@ -35,8 +35,6 @@ OLIVE_NAMESPACE_ENTER
 KeyframeViewBase::KeyframeViewBase(QWidget *parent) :
   TimelineViewBase(parent),
   dragging_bezier_point_(nullptr),
-  y_axis_enabled_(false),
-  y_scale_(1.0),
   currently_autoselecting_(false)
 {
   SetDefaultDragMode(RubberBandDrag);
@@ -57,22 +55,6 @@ void KeyframeViewBase::Clear()
   item_map_.clear();
 }
 
-const double &KeyframeViewBase::GetYScale() const
-{
-  return y_scale_;
-}
-
-void KeyframeViewBase::SetYScale(const double &y_scale)
-{
-  y_scale_ = y_scale;
-
-  if (y_axis_enabled_) {
-    VerticalScaleChangedEvent(y_scale_);
-
-    viewport()->update();
-  }
-}
-
 void KeyframeViewBase::DeleteSelected()
 {
   QUndoCommand* command = new QUndoCommand();
@@ -194,7 +176,7 @@ void KeyframeViewBase::mouseMoveEvent(QMouseEvent *event)
 
           keypair.key->key()->set_time(node_time);
 
-          if (y_axis_enabled_) {
+          if (IsYAxisEnabled()) {
             keypair.key->key()->set_value(keypair.value - mouse_diff_scaled.y());
           }
 
@@ -257,7 +239,7 @@ void KeyframeViewBase::mouseReleaseEvent(QMouseEvent *event)
                                                 command);
 
             // Commit value if we're setting a value
-            if (y_axis_enabled_) {
+            if (IsYAxisEnabled()) {
               item->key()->set_value(keypair.value);
               new NodeParamSetKeyframeValueCommand(item->key(),
                                                    keypair.value - mouse_diff_scaled.y(),
@@ -288,10 +270,6 @@ void KeyframeViewBase::ScaleChangedEvent(const double &scale)
   }
 }
 
-void KeyframeViewBase::VerticalScaleChangedEvent(double)
-{
-}
-
 const QMap<NodeKeyframe *, KeyframeViewItem *> &KeyframeViewBase::item_map() const
 {
   return item_map_;
@@ -310,11 +288,6 @@ void KeyframeViewBase::TimeTargetChangedEvent(Node *target)
   }
 }
 
-void KeyframeViewBase::SetYAxisEnabled(bool e)
-{
-  y_axis_enabled_ = e;
-}
-
 void KeyframeViewBase::SetKeyframeTrackVisible(int track, bool visible)
 {
   if (!visible == hidden_tracks_.contains(track)) {
@@ -336,6 +309,11 @@ void KeyframeViewBase::SetKeyframeTrackVisible(int track, bool visible)
   }
 }
 
+void KeyframeViewBase::ContextMenuEvent(Menu& m)
+{
+  Q_UNUSED(m)
+}
+
 rational KeyframeViewBase::CalculateNewTimeFromScreen(const rational &old_time, double cursor_diff)
 {
   return rational::fromDouble(old_time.toDouble() + cursor_diff);
@@ -433,7 +411,7 @@ void KeyframeViewBase::ProcessBezierDrag(QPointF mouse_diff_scaled, bool include
 QPointF KeyframeViewBase::GetScaledCursorPos(const QPoint &cursor_pos)
 {
   return QPointF(static_cast<double>(cursor_pos.x()) / GetScale(),
-                 static_cast<double>(cursor_pos.y()) / y_scale_);
+                 static_cast<double>(cursor_pos.y()) / GetYScale());
 }
 
 void KeyframeViewBase::ShowContextMenu()
@@ -480,7 +458,11 @@ void KeyframeViewBase::ShowContextMenu()
         break;
       }
     }
+  }
 
+  ContextMenuEvent(m);
+
+  if (!items.isEmpty()) {
     m.addSeparator();
 
     QAction* properties_action = m.addAction(tr("P&roperties"));
@@ -532,7 +514,7 @@ void KeyframeViewBase::ShowKeyframePropertiesDialog()
 
 void KeyframeViewBase::AutoSelectKeyTimeNeighbors()
 {
-  if (currently_autoselecting_ || y_axis_enabled_) {
+  if (currently_autoselecting_ || IsYAxisEnabled()) {
     return;
   }