dxf → vector Relation

File in src/core/dxf	Includes file in src/core/vector
qgsdxfexport.cpp	qgsvectordataprovider.h
qgsdxfexport.cpp	qgsvectorlayer.h
qgsdxfexport_p.h	qgsvectorlayer.h
qgsdxfexport_p.h	qgsvectorlayerfeatureiterator.h