Click and drag around a bit (release selection outside designed window) and you get this rubber marks left.
A single click on the window also leaves a rubber mark.
Dragging and then releasing the mouse button outside the scroll area causes does not cancel the drag.
I reported this already, but you appear to have deleted it!!
[Bug alpha 16 Windows] Canceled selection leaves rubber mark
Re: [Bug alpha 16 Windows] Canceled selection leaves rubber
I've noticed this too, when you click somewhere. I had to check in the object
list to see if an actual 1x1 pixel object was created, but it wasn't. Phew!
list to see if an actual 1x1 pixel object was created, but it wasn't. Phew!

I compile using 5.31 (x86) on Win 7 Ultimate (64-bit).
"PureBasic won't be object oriented, period" - Fred.
"PureBasic won't be object oriented, period" - Fred.