implemented base transition support

While very much incomplete, transitions can now be created and will render
correctly.

app/node/block/block.cpp

@@ -22,6 +22,8 @@
 
 #include <QDebug>
 
+#include "transition/transition.h"
+
 Block::Block() :
   previous_(nullptr),
   next_(nullptr)
@@ -159,8 +161,16 @@ rational Block::MediaToSequenceTime(const rational &media_time) const
 void Block::CopyParameters(const Block *source, Block *dest)
 {
   dest->set_block_name(source->block_name());
-  dest->set_length(source->length());
   dest->set_media_in(source->media_in());
+
+  if (source->type() == kTransition && dest->type() == kTransition) {
+    const TransitionBlock* src_t = static_cast<const TransitionBlock*>(source);
+    TransitionBlock* dst_t = static_cast<TransitionBlock*>(dest);
+
+    dst_t->set_in_and_out_offset(src_t->in_offset(), src_t->out_offset());
+  } else {
+    dest->set_length(source->length());
+  }
 }
 
 void Block::Link(Block *a, Block *b)

app/node/block/transition/crossdissolve/crossdissolve.cpp

@@ -7,7 +7,11 @@ CrossDissolveTransition::CrossDissolveTransition()
 
 Node *CrossDissolveTransition::copy() const
 {
-  return new CrossDissolveTransition();
+  CrossDissolveTransition* c = new CrossDissolveTransition();
+
+  CopyParameters(this, c);
+
+  return c;
 }
 
 QString CrossDissolveTransition::Name() const

app/node/block/transition/transition.cpp

@@ -51,14 +51,19 @@ void TransitionBlock::set_length_and_media_in(const rational &length)
   abort();
 }
 
-void TransitionBlock::set_in_offset(const rational &in_offset)
+const rational &TransitionBlock::in_offset() const
 {
-  in_offset_ = in_offset;
-  RecalculateLength();
+  return in_offset_;
 }
 
-void TransitionBlock::set_out_offset(const rational &out_offset)
+const rational &TransitionBlock::out_offset() const
 {
+  return out_offset_;
+}
+
+void TransitionBlock::set_in_and_out_offset(const rational &in_offset, const rational &out_offset)
+{
+  in_offset_ = in_offset;
   out_offset_ = out_offset;
   RecalculateLength();
 }

app/node/block/transition/transition.h

@@ -12,7 +12,6 @@ public:
   virtual QString Category() const override;
 
   NodeInput* out_block_input() const;
-
   NodeInput* in_block_input() const;
 
   virtual void Retranslate() override;
@@ -20,8 +19,9 @@ public:
   virtual void set_length(const rational &length) override;
   virtual void set_length_and_media_in(const rational &length) override;
 
-  void set_in_offset(const rational& in_offset);
-  void set_out_offset(const rational& out_offset);
+  const rational& in_offset() const;
+  const rational& out_offset() const;
+  void set_in_and_out_offset(const rational& in_offset, const rational& out_offset);
 
 private:
   void RecalculateLength();