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When will the "can't drop this VI in that empty space in the diagram" bug be fixed?


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The title is made up, but explains what I have been experiencing for years, hoping that it would be fixed in the next version, but it never has, so I am starting to suspect nobody is caring or possibly maybe nobody even noticed it?

Anyway, the symptoms are:

when I drag a VI (from either a palette or from the icon of an open VI) into a target VI's diagram, I am frequently encountering this odd and annoying 🚫 symbol where my cursor is (it's not red and it is slanted the other way, but this is the closest emoji to the real thing I could find), instead of the "androgynous" cursor (a mix of ♀️and ♂️) which tells me that I am going to copy that object where the cursor is.

I would move the cursor around, seeing a 🚫 wherever I go, until I would fleetingly grasp a cursor with the + index (the "androgynous" cursor) over some random location, and then, painstakingly try to go back to that region to find the sweet spot (pixel really) where I am able to drop the VI. Of course, once dropped on the diagram I can move the VI anywhere where I was forbidden to drop it during my initial attempts.

That's got to be the most annoying bug in a graphical programming environment ever...

Am I the only one to experience this?

I am using 2019 SP1 64 bit, but that has been around for several versions already.

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I have never seen such behavior in any version of LabVIEW. That said, I use 32 bit. Perhaps it's specific to 64 bit?

If Windows scaling is enabled, try disabling it. I had strange behavior because of that in the past.

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Here is the video illustrating the symptoms.

Of course the demo effect wants that the first time I try to drop the subVI, the cursor looks fine (I had just verified on a brand new VI that the symptom appeared right away, and after I went through the recording hoops, I had to "work" for it to show up), but a brief excursion with the cursor over the project (from which the subVI came, so indeed I could not drop it again in there) was enough for the cursor to turn back to the "forbidden" icon.

I am not sure that is very visible in the video, but there is a little bit of a "stuttering" and you can usually very briefly see the arrow+ cursor alternating with the forbidden icon.

The bottomline though is that I cannot drop the subVI in most of the virgin diagram and have to actively search for allowed drop zone.

I have come to get used to it now, but it is definitely getting old and a productivity hog.


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9 hours ago, LogMAN said:

If Windows scaling is enabled, try disabling it. I had strange behavior because of that in the past.

No scaling enabled that I know of. I am using a VM in Parallels Desktop running on a MBP,  but I would be surprised it is the root cause.

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9 hours ago, Neil Pate said:

How frequently? I must say I cannot recall seeing this, certainly not regularly enough for it to be a nuisance. Can you post a video?

Frequently enough that in my drive to make this world a better place, I decided this was a worthy campaign to galvanize the crowds for.

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I agree with @hooovahh. This is likely an issue with Parallels. I don't have a VM to try this, but I assume that your cursor leaves the VM for a brief moment (the "stuttering"), which causes this strange behavior. Parallels probably buffers the cursor info and restores it in a way that is incompatible with LV.

Does Parallels allow you to "capture" the cursor, so that it can't leave the VM without pressing some master key? I can imagine this fixes the issue.

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Parallels has a few bugs up its sleeves too, so I am willing to lean toward that conclusion too considering that no one seems to have observed this.

Is anyone using Parallels Desktop in "Coherence" mode and observing this phenomenon? There is no Windows' real estate per se in this mode, each Windows app's window appears as a regular macOS one (with the Windows style though), so I can't really imagine that the OSes could be mislocating the cursor... but this is all beyond my technical knowledge to really ponder.

Thanks for looking into it though.

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  • 3 weeks later...

I remember some similar issues in the past on plain Windows. Not exactly the same but it seemed to have to do with the fact that LabVIEW somehow didn't get the Window_Enter and Window_Leave events from Windows anymore or at least not properly. And it wasn't just LabVIEW itself but some other applications started to behave strange too. Restarting Windows usually fixed it. And at some point it went away just as it came, most likely a Windows update or something.

So I think it is probably something about your VM environments cursor handling that gets Windows to behave in a way that doesn't sit well with LabVIEW.

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