When using get_tree().input_event(ev), the engine will JUST send the event down the SceneTree.
However, you won't get any of the benefits of the Input singleton:
- No InputMap actions will be emitted
- The internal input state won't be modified, so methods like `Input.get_mouse_pos()` or `Input.is_joy_button_pressed` won't return the expected output after sending the event.
This is fixed by using `Input.parse_input_event(ev)` instead.
I guess we'll also have to update the docs to reflect that this is the preferred method of sending custom InputEvents.
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