I am running 12.32 on the latest win 10 machine. For my photos I use an open source program called XnViewMP. I am running its current version. If I have its slide sorter open on one screen and Opus on the other I am unable to drag an icon from the sorter to a folder in Opus. I can highlight the icon and copy it with Ctrl-C and then paste it, but dragging does not work. I opened Explorer and it drags just fine.
Make sure Opus isn't running elevated (it will say "ADMINISTRATOR" in the window title if it is), as that can block drag & drop from non-elevated applications.
Turning off Preferences / Miscellaneous / Advanced [Compatibility]: dragdrop_async is also worth a try, in case that helps. (Reset it back to normal if it doesn't help.)
Leo, you are quick. Thank you. Is there a disadvantage to async off or a situation in which I would need it on?
It can tie up the window while processing drops.
Did it make a difference? If it did, we can look into making it automatic when drops come from that particular program, so it can be left in the default setting for everything else.
Leo,
Sorry I had forgotten to say. Yes, switching to async did solve the problem thank you. I appreciate you offering to fix it for XnViewMP. Is that a problem they should fix at their end or is it easy for you to correct? I could contact XnView if you can advise what the problem is.
Not sure what you mean be tie up the window while processing drops. Does that just mean a slightly slower response time on that on particular procedure, i.e. dragging and dropping?
I need to look at it in more detail to be sure, but it's probably something we need to fix, not them.
Although they could change their code to work with what we're doing, and most things do work with it, what we're doing is slightly outside the spec (or not covered by the spec either way, from what I remember) so there's no reason they have to, and we should really be the ones ensuring compatibility here.
We can usually detect which program is dropping files on us and disable the async mode if it's needed.
I am impressed with you and Opus like usual. Just as an aside I would think that you having to keep track of a limitless number of program to assure compatibility is a large issue. What should I look for in the future or you bug fix list to know this is fixed and I can restore my setting?
It'll be in the next update. 
Too kind. Thank you..
1 Like
Leo, no big deal, but I updated to 12.33 and if I reset Async to True the drag and drop still does not work. I need to keep it on False to work. Thought you might want to know.
It was working OK when I tested it. Don't have time to re-install XnView and re-test it at the moment as we're super busy with the public beta for 13.
Same here (XnViewMP 1.5.5 and Opus 12.33).
The good news: works in v13 
No problem. I will wait for 13
You could sign up for free for the 90 trial of DO 13 beta, right now.
Leo, there is one other drag and drop issue with Opus 12.33 and XnViewMP. When I have a zip file of folders that I have downloaded, and I click on the zip to open its contents, I can select any or all of the contents (photos) and drag them to another folder in Opus, but I can't drag them to the Xn slide sorter. To get them to the sorter I have to drag them out of the zip to any other folder showing in Opus, and then I can drag them to XnView.
This problem seems like it might be related to the one reported above regarding not being able to drag from Xn to Opus, however, I have implemented the fix you gave me to solve that problem; it does not seem to solve this one.
Maybe this too will be corrected in Opus 13. Thank you.
XnViewMP probably can't read from zip files. Does it work if you open the archives in File Explorer and drag from there?
hmmm. Opening the zip in Explorer has the same issue as with Opus. I hadn't thought to try that since the prior issue, dragging from Xn to Opus failed, but from Xn to Explorer worked fine.
Just wanted to confirm your note Ixp - drag and drop from XnViewMP 1.8.2 to Opus 13.10 works fine with dragdrop_async set to True. Thanx again.