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/timelinewidget/timelinescaledobject.cpp

@@ -27,6 +27,8 @@
 
 OLIVE_NAMESPACE_ENTER
 
+const int TimelineScaledObject::kCalculateDimensionsPadding = 10;
+
 TimelineScaledObject::TimelineScaledObject() :
   scale_(1.0),
   min_scale_(0),
@@ -112,6 +114,21 @@ void TimelineScaledObject::SetScale(const double& scale)
   ScaleChangedEvent(scale_);
 }
 
+void TimelineScaledObject::SetScaleFromDimensions(double viewport_width, double content_width)
+{
+  SetScale(CalculateScaleFromDimensions(viewport_width, content_width));
+}
+
+double TimelineScaledObject::CalculateScaleFromDimensions(double viewport_sz, double content_sz)
+{
+  return static_cast<double>(viewport_sz / kCalculateDimensionsPadding * (kCalculateDimensionsPadding-1)) / static_cast<double>(content_sz);
+}
+
+double TimelineScaledObject::CalculatePaddingFromDimensionScale(double viewport_sz)
+{
+  return (viewport_sz / (kCalculateDimensionsPadding * 2));
+}
+
 TimelineScaledWidget::TimelineScaledWidget(QWidget *parent) :
   QWidget(parent)
 {