A presentation page is a rectangle in a page space. Its lower-left corner is always positioned at the origin of the page space.
An application can determine the dimensions of the presentation page by calling GpiQueryPS. It returns a pointer to a SIZEL structure that contains the page dimensions. If an application specifies arbitrary page units when creating a presentation space with GpiCreatePS, the page viewport is constructed such that the origin of the page rectangle maps to the origin of the default device rectangle and either the right or top edge maps to the corresponding edge. Thus, the aspect ratio of the graphic is preserved.
If either the height or width of the presentation page is set to 0 (using GpiCreatePS), the application must set GPIA_ASSOC to set the default presentation page size to the default device rectangle size.