on_key

The on_key method defines callback behavior that is triggered when a key is pressed/released/held while a Window has input focus. It generates a CrystGLFW::Event::WindowKey that is yielded to the block:

window = Window.new

window.on_key do |event|
  key = event.key
  if event.action.press?
    if key.printable?
      puts "#{key.name} was pressed"
    else
      puts "an unprintable key was pressed"
    end
  end  
end

With this callback defined, every time a key is pressed while window has input focus, the key's name is printed to standard output if the key is printable.

on_key must be called from within a run block definition.