renderer: improved code flow

app/threading/threadticket.h

@@ -27,12 +27,13 @@
 
 #include "codec/frame.h"
 #include "codec/samplebuffer.h"
+#include "common/cancelableobject.h"
 #include "common/timerange.h"
 #include "node/output/viewer/viewer.h"
 
 namespace olive {
 
-class RenderTicket : public QObject
+class RenderTicket : public QObject, public CancelableObject
 {
   Q_OBJECT
 public:

app/threading/threadticketwatcher.cpp

@@ -88,6 +88,13 @@ bool RenderTicketWatcher::HasResult()
   }
 }
 
+void RenderTicketWatcher::Cancel()
+{
+  if (ticket_) {
+    ticket_->Cancel();
+  }
+}
+
 void RenderTicketWatcher::TicketFinished()
 {
   emit Finished(this);

app/threading/threadticketwatcher.h

@@ -46,6 +46,8 @@ public:
 
   bool HasResult();
 
+  void Cancel();
+
 signals:
   void Finished(RenderTicketWatcher* watcher);