Diagram.documentBounds:

Diagram.contentAlignment:
None Center
Left Right
Top Bottom

Diagram.position:

Diagram.scale:

Diagram.fixedBounds (x, y, width, height):

Diagram.padding (top, right, bottom, left):

Diagram.autoScale:
Diagram.None
Diagram.Uniform
Diagram.UniformToFill
(but no greater than CommandHandler.defaultScale)

A Diagram's Diagram.contentAlignment property determines how parts are positioned when the Diagram.viewportBounds width or height is different than the Diagram.documentBounds width or height.