Class: Input

User inputs handler.

This sybsystem registers Input compoments, listening to all user inputs and interpret events into UserCmds.

1. Commands Handling Process

This class is always updated by x-visual frame. Each time updated, the buffering UI events will be converted to commands and saved in xview's command queue. The next time updating, the command queue will be cleared.

In x-visual 0.2, the xview is changed to a global accessable singleton. The command queue must not been modified other than by Input.

Xview is also exported as xworld property, xv.xworld.xview.

2. About Gpu Picking

If there is a GpuPickable component in an entity, his class also put mouse position into it.

If GPU picking is not needed, user should provide x parameter of constructor a dummy mouse event handler. (TODO test)

Create Input handler of 'xview'.