I'm going to add actions to these methods in order to enable the possibility to add hotkeys to them. Thanks for pointing this out.
Using the space as hotkey for checking/uncheking the file will be possible, but the user will need to manually assign that shortcut to that action, using the preferences dialog. The space and shift+space are standard Windows hotkeys to page-down and page-up read only content, used by many programs, and that's what you are experiencing with the grid.