Callback Function

• The callback function is a normal callback function for that widget
• It makes a dynamic call to Java code for the peer object by

  JAVA_UPCALL((EE(), (void *)client_data, 
                  "method", "(arg-types)V",
                  args...))
  

• Each arg type is defined in src/share/java/include/signature.h
  • I - integer
  • B - byte
  • C - char, etc
  • "I" - integer string
  • "C" - char string, etc
• For ComboBox we would like to use its value - a string - but can't (yet?). So call a void method

  JAVA_UPCALL((EE(), (void *)client_data, 
                  "action", "()V"))
  

  calls method action() in the peer.