Normally the origin of the canvas coordinate system is at the
upper-left corner of the window containing the canvas.
It is possible to adjust the origin of the canvas
coordinate system relative to the origin of the window using the
xview and yview widget commands; this is typically used
Canvases do not support scaling or rotation of the canvas coordinate
system relative to the window coordinate system.
Indidividual items may be moved or scaled using widget commands
described below, but they may not be rotated.