Operating system: Ubuntu Linux. Versions 16.04 and 18.04
Graphics card: irrelevant (happened on multiple systems, with both NVIDIA or integrated INTEL graphics)
Broken: 2.80, 387c1f2e0d5d
I believe that I have seen this happening already on 2.79. For sure it was already happening on 2.80 Alpha.
Short description of error
Sometimes, expecially while or after having run very resource-intensive operations, Blender would start interpreting mouse and keyboard input in a strange way.
For example, numpad 1/3/7 won't change the view, and clicking on the frame bar of the timeline won't advance frames.
Some other inputs would have an effect, just not the intended one.
(I can't remember an example right now, but up until some versions ago using the mouse wheel in the viewport would change frame instead of zooming)
This happens quite consistently when the system has used a lot of resources. I have waited to open a bug because I've recently changed machine and I have more resources, but I've reached that point again and it has happened again.
Note: in my workflow I usually have Blender on a workspace, and other stuff in other workspaces (workspaces on Ubuntu are "expansions" of the desktop, made to organize windows), and I go back to check on Blender by using Ctrl+Alt+(←↓→↑) depending on where the workspace is. So maybe Blender is catching some of these keystrokes?
I've found that one way to restore normal operation is by hitting "Alt" on the keyboard several times.
Exact steps for others to reproduce the error
Unfortunately it's difficult to reproduce quickly, but I believe it happens consistently (has happened to me on two computers)
- Open Blender
- Create a basic but very memory intense simulation (i.e. use quick fluid on the default cube and crank up the resolution)
- Leave it to run and work on something else on a different workspace
- (unfortunately I haven't been able to quantify this) when Blender has been using a lot of resources for a while, go back to the workspace using Ctrl+Alt+arrow
- Zoom in/out or change frame using the mouse. It won't work as intended.
- Hit Alt several times, it will restore normal operation.