Description Thomas Singer 2019-03-19 03:28:19 EDT

A user reported following exception against SmartGit 18.2.6 (which uses SWT 4.922) on macOS 10.13.6:

org.eclipse.swt.SWTException: Data does not have correct format for type
	at org.eclipse.swt.dnd.DND.error(DND.java:290)
	at org.eclipse.swt.dnd.DND.error(DND.java:241)
	at org.eclipse.swt.dnd.FileTransfer.javaToNative(FileTransfer.java:73)
	at org.eclipse.swt.dnd.DragSource.pasteboard_provideDataForType(DragSource.java:745)
	at org.eclipse.swt.dnd.DragSource.dragSourceProc(DragSource.java:537)
	at org.eclipse.swt.internal.cocoa.OS.objc_msgSendSuper(Native Method)
	at org.eclipse.swt.widgets.Display.applicationNextEventMatchingMask(Display.java:5188)
	at org.eclipse.swt.widgets.Display.applicationProc(Display.java:5612)
	at org.eclipse.swt.internal.cocoa.OS.objc_msgSend(Native Method)
	at org.eclipse.swt.internal.cocoa.NSApplication.nextEventMatchingMask(NSApplication.java:97)
	at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3732)

The user's description is:
The most probable culprit was that I was using an application called
Synergy.  It's an application that lets you share a single
keyboard+mouse across multiple computers. I have Synergy server
installed on a PC and a client on a Mac, and this lets me drag the mouse
pointer between my Mac's desktop on my Mac monitor and my PC desktop on
my PC monitor.  The mouse+keyboard are connected to the PC, and once the
mouse leaves the side of the PC desktop all mouse + keyboard messages
are transferred via network to the Mac Synergy client on the Mac which
acts as a virtual mouse + keyboard there.  And also the reverse, which
is where the SmartGit bug happened.

The bug occurred when I dragged an XCode window on the Mac desktop to
the very edge of the Mac desktop; once the mouse left the Mac desktop
and was taken back to the PC desktop, the XCode window was left behind
(you of course can't drag app windows between hosts).  At that time I
had SmartGit maximized on the Mac, so it could very well be that Synergy
performed a drop operation of the dragged XCode window onto the
rightmost pixel edge of the maximized SmartGit window.

I did try to reproduce it a few times shortly after (leave the monitor
at specific heights, once for every control region of the SmartGit
window, as well as dragging other windows), but failed on every attempt...

This happened on a development PC of a client of mine; I wouldn't mind
testing out a few other things, but I won't be able to do so until I get
back to him somewhere at the start of next week.  I don't know what
version of MacOS is on that machine (I'm definitely not a Mac
developer/user).

My bet would be on Synergy's handling/generating of the mouse messages;
maybe it generates a Drop message once you drag something around and
leave that desktop?  The fact that it was an XCode window seems
irrelevant to me?  Then again Synergy also handles copy/paste clipboard
transfer between hosts, and also (just checked - didn't know of Synergy
myself until yesterday) dragging files between hosts, so that might also
be the trigger?