Drive action state from UI

[alice-i-cecile]

What problem does this solve?

Drive action state by clicking buttons in the UI.

What solution would you like?

Lay out what an ideal solution would look like, from a user-facing perspective.

How could this be implemented?

Create an example to document directly modifying ActionState based on events sent by UI clicks.

What alternatives have you considered?

Create an UserInput variant that can store arbitrary events, which can be read or processed.

However, this is less than useful: any system that this plugin create cannot have automatic access to the corresponding event: work is required at compile time.

Related work

Once bevyengine/bevy#142 is solved this should be revisited: dynamically adding systems to correspond to new mapped event types may be feasible.

[alice-i-cecile]

If we skip the intermediate Event layer we can get a first-class solution!