In some (but not all) circumstances, GUI elements get confused when they are active (mouse down) in the middle of a drag and the mouse leaves the window. They seem to lose track of a mouse up button, never receive it, and thus the GUI element stays active.
- Choose a documentation pages (e.g., Procedural Textures | Babylon.js Documentation )
- Click on the demo on in the right column, but DO NOT choose the full window option.
- In the demo subwindow, drag one of the sliders to the right so that the pointer leaves the subwindow.
- Release the mouse outside of the subwindow.
- Now move the mouse back into the subwindow. Notice that the slider is still tracking the mouse.
- You’re now stuck. There seems to be no way of getting out of this state.
I have seen this behavior happen with GUI controls and gizmos. It doesn’t appear to happen when the demo is full-window and the mouse falls outside the browser window.