Input event type for mouse button events.
Contains mouse click informations. See [method Node._input].
http://docs.godotengine.org/en/3.0/learning/features/inputs/mouse_and_input_coordinates.html
Mouse button identifier, one of the BUTTON_* or BUTTON_WHEEL_* constants in [@GlobalScope].
If [code]true[/code] the mouse button's state is a double-click. If [code]false[/code] the mouse button's state is released.
TO TALK in PR, reduz said : i think it's used for apple touch but i don't remember what it does
If [code]true[/code] the mouse button's state is pressed. If [code]false[/code] the mouse button's state is released.