Thanks for your fast reply. Yes, the example uses svg and the "qt5waybutton.cpp" includes "qtsvgpixmapcache.h". I have tried to put the line that you told me in the .pro, and the result is the same. ¿Have i do something else with the svg module?The .pro is the next:

Qt Code: 
  1. CONFIG      += designer plugin 
  2. TARGET      = $$qtLibraryTarget($$TARGET)
  3. TEMPLATE    = lib
  4. QT += svg
  5. QTDIR_build:DESTDIR     = $$QT_BUILD_TREE/plugins/designer
  6.  
  7.  
  8. HEADERS     = qt5waybutton.h \
  9.               qt5waybuttonplugin.h \
  10. SOURCES     = qt5waybutton.cpp \
  11.               qt5waybuttonplugin.cpp
  12.  
  13. # install
  14. target.path = $$[QT_INSTALL_PLUGINS]/designer
  15. sources.files = $$SOURCES $$HEADERS *.pro
  16. sources.path = $$[QT_INSTALL_EXAMPLES]/designer/qt5waybuttonplugin
  17. INSTALLS += target sources
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Sorry, i am a bit new in this.