A canvas which forwards drawing commands to sub-canvases.
addCanvas:
clipRect
Return the currently active clipping rectangle
removeCanvas:
allocateForm:
Allocate a new form which is similar to the receiver and can be used for accelerated blts
depth
depth:
set the extent to be used with this canvas
extent
Return the physical extent of the output device
extent:
initialize
apply:
evaluate aBlock with a canvas to do a drawing command on. See implementors for examples
contentsOfArea:into:
Return the contents of the given area
new
Answer a new instance of the receiver (which is a class) with no indexable variables. Fail if the class is indexable.
