Use forward declaration where possible.

src/app/puzzle/vpuzzlelayout.cpp

@@ -26,6 +26,7 @@
  **
  *************************************************************************/
 #include "vpuzzlelayout.h"
+#include "vpuzzlelayer.h"
 
 //---------------------------------------------------------------------------------------------------------------------
 VPuzzleLayout::VPuzzleLayout() :

src/app/puzzle/vpuzzlelayout.h

@@ -31,9 +31,11 @@
 #include <QSizeF>
 #include <QMarginsF>
 #include <QList>
-#include "vpuzzlelayer.h"
+
 #include "def.h"
 
+class VPuzzleLayer;
+
 // is this the right place for the definition?
 enum class FollowGrainline : qint8 { No = 0, Follow90 = 1, Follow180 = 2};
 

src/app/puzzle/xml/vpuzzlelayoutfilewriter.cpp

@@ -27,6 +27,10 @@
  *************************************************************************/
 
 #include "vpuzzlelayoutfilewriter.h"
+#include "vpuzzlelayout.h"
+#include "vpuzzlelayer.h"
+#include "vpuzzlepiece.h"
+#include "layoutliterals.h"
 
 //---------------------------------------------------------------------------------------------------------------------
 VPuzzleLayoutFileWriter::VPuzzleLayoutFileWriter()

src/app/puzzle/xml/vpuzzlelayoutfilewriter.h

@@ -31,9 +31,10 @@
 
 #include <QXmlStreamWriter>
 #include "../ifc/xml/vabstractconverter.h"
-#include "vpuzzlelayout.h"
+
-#include "vpuzzlelayer.h"
+class VPuzzleLayout;
-#include "vpuzzlepiece.h"
+class VPuzzleLayer;
+class VPuzzlePiece;
 
 class VPuzzleLayoutFileWriter : public QXmlStreamWriter
 {