If the object has not been created yet and has been initialized
correctly, insert it for real in the parent canvas
created
Answer whether the object is just a placeholder or has already
been inserted for real in the parent canvas
lower
Move the item to the lowest position in the display list.
Child widgets always obscure other item types, and the stacking
order of window items is determined by sending methods to the
widget object directly.
raise
Move the item to the highest position in the display list.
Child widgets always obscure other item types, and the stacking
order of window items is determined by sending methods to the
widget object directly.
redraw
Force the object to be displayed in the parent canvas, creating
it if it has not been inserted for real in the parent, and refresh
its position if it has changed.
remove
Remove the object from the canvas
show
Ensure that the object is visible in the center of the canvas,
scrolling it if necessary.