Basically what the title says. This is slightly annoying when you’re switching between many assets and instead just end up with a new window. Occasionally this will cause the engine to halt for a few seconds with a half-opaque black rectangle being where the unexpected window should be. Another (rare) effect is a straight up crash to desktop with no error reporter.
Steps to reproduce the issue:
Have multiple tabs attached to a window.
Click (don’t hold!) a tab and shortly afterwards move the mouse far enough away that it would detach the tab.
End up with another window instead of having switched the tab.
It happens with any number of tabs for me, but it usually happens the most when there is one large level and a few material and mesh tabs open. It happens with any kind of window, most easily reproduced in a maximized/fullscreen window.
I have not been able to reproduce this so let me get a few more details…
Please provide your system Specs: Dxdiag if on a PC, Mac: Apple menu >About This Mac>More Info> Add the information from this window (serial # not necessary).
About how many tabs should I have open when testing (I tested with around 3-6 tabs open)
Should the Window housing the tabs be full screen or a floating window?
I’ll try to repro this again with these provided specifications.
It’s a 5-button 3200 dpi scriptable mouse, but I don’t think that is causing it. This behavior is exclusive to Unreal Engine. Unity, Chrome, Windows Explorer, etc all work fine.
Testing with a custom mouse here, we found it much easier to accidentally drag off a tab because of the sensitivity of the mouse. While I’m not saying that is what is happening on your end, I’m curious if there is a conflict between UE4 and possibly the drivers for that specific mouse. Do you have a generic mouse you can temporarily plug in and test this bug with?
I do have a generic PS/2 mouse here, but had to test on an older system - I was able to reproduce it at a near 80% rate, which is probably due to the low polling frequency for mouse events, turning release and move into one event. If my observation is correct here, it happens more frequently on slower systems.
I tried again today without the CPU and GPU overclocked and was still able to reproduce the issue. Here is a video of me trying it in Unreal Engine (and succeeding) and then in Visual Studio (and failing). The settings used for the mouse are 3200DPI, 1000hz polling frequency and 1ms response time to make sure that it isn’t a mouse event that was received at the same time.
I’m helping out on trying to reproduce the issue you’re seeing.
As far as the black rectangle / freeze goes, I’ve only gotten it to happen once. The tab being dragged out from clicking quickly and then moving the mouse doesn’t seem like a bug however. As you mentioned with your slower mouse. I’ve been able to get this to happen with Google Chrome and Microsoft Explorer as well however. It seems like an issue of the mouse registering the click and movement as a click and drag due to it being so quick that the program, when in a laggy state, registers them as one action and counts it as a drag, as you mentioned.
I retried reproducing the issue in Google Chrome and Microsoft Explorer, but had no success. Even my own tool to monitor current state of the mouse had no trouble separating press, release and move using window events. What does Unreal Engine use to detect input?
It uses the Windows API from what I remember. I’m still having no issues reproducing the dragging with both Chrome and Mozilla, about the same frequency as UE4. I’ve run into the black rectangle issue once more. I’ll put a bug in for that and be sure that I’m the one who picks it up after the fix, so that I can be sure it gets tested enough since the repro rate is so low.
I also managed to come across another bug while testing this, that can be found here: UE-34895 I’ll reply shortly with the bug for the black rectangle issue.
I’ve placed the bug report in for the freezing issue with dragging the tabs outs quickly. You can find at this link: UE-35065. The general action of clicking and quickly dragging causing the tabs to become undocked/docked isn’t a bug however so I’ll be marking this as resolved with those two bugs entered.
I forgot to update this. A user on reddit figured out that the issue came from outdated project binaries, now it doesn’t happen anymore. Also my project launch time is down to <2 minutes from over 3 hours. So hooray for people that find solutions!
Glad to hear that you were able to find the solution to the problem. I likely never would’ve come across that since it was never mentioned that it was project specific, although I should’ve asked.
