FULL PRODUCT VERSION :
java version "1.8.0_151"
Java(TM) SE Runtime Environment (build 1.8.0_151-b12)
Java HotSpot(TM) 64-Bit Server VM (build 25.151-b12, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows [Version 6.1.7601]

EXTRA RELEVANT SYSTEM CONFIGURATION :
[insignificant]

A DESCRIPTION OF THE PROBLEM :
Trying to drag and drop from a SWT control to the FXCanvas succeeds only once, because of a false assertion in class com.sun.javafx.tk.quantum.EmbeddedSceneDT [line 62]: assert dragSource == null;

The instance of EmbeddedSceneDT is once initialized and then recycled, but dragSource gets never set to null after a DnD operation.

 

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Craete a small SWT / JavaFX hybrid with DnD Support from a SWT control to JavaFX. Enable assertions and try DnD more once.
After the first DnD operation all subsequent one will fail due to the false assertion.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
no assertion fault after multiple DnD operations
ACTUAL -
after the first DnD allsubsequnt attempts fail

ERROR MESSAGES/STACK TRACES THAT OCCUR :
java.lang.AssertionError
at com.sun.javafx.tk.quantum.EmbeddedSceneDT.lambda$handleDragEnter$317(EmbeddedSceneDT.java:62)
at com.sun.javafx.tk.quantum.EmbeddedSceneDnD.executeOnFXThread(EmbeddedSceneDnD.java:101)
...

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
[not applicable]
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CUSTOMER SUBMITTED WORKAROUND :
disable assertions, which is undesirable for me