on_toggle_focus

The on_toggle_focus method defines callback behavior that is triggered when a window's "focus" is toggled. It generates a CrystGLFW::Event::WindowToggleFocus that is yielded to the block:

window = Window.new

window.on_toggle_focus do |event|
  if event.focused?
    puts "Window is focused!"
  else
    puts "Window is out of focus!"
  end
end

With this callback defined, every time the focus of window is toggled, it prints whether or not it is focused to standard output.

on_toggle_focus must be called from within a run block definition.