wx:register-collecting-blit

Registers a blit to occur when garbage collection starts or ends.

• (wx:register-collecting-blit canvas x y w h on off on-x on-y off-x off-y) -> void
      canvas : wx:canvas% object
      x : inexact real
      y : inexact real
      w : inexact real
      h : inexact real
      on : wx:memory-dc% object
      off : wx:memory-dc% object
      on-x = 0 : inexact real
      on-y = 0 : inexact real
      off-x = 0 : inexact real
      off-y = 0 : inexact real

  When garbage collection starts, (send (send canvas get-dc) blit x y w h on on-x on-y) is called. When garbage collection ends, (send (send canvas get-dc) blit x y w h off off-x off-y) is called.

  The canvas is registered weakly, so it will be automaticall unregistered if the canvas becomes invisible and inaccessible. Multiple registrations can be installed for the same canvas.

  See also wx:unregister-collecting-blit.