公开(公告)号：CA1236603A

公开(公告)日：1988-05-10

申请号：CA480976

申请日：1985-05-07

Applicant: IBM

Inventor： JOHNSON PETER W ,  NIBLETT PETER D

IPC: G06F3/048 ,  G06F3/14 ,  G09G5/14 ,  G09G3/20

Abstract: A method and apparatus for automatically changing the display in overlapping rectangular viewport areas of a display screen of a digital display apparatus and in which each viewport area is assigned a different priority level. The method includes the steps of a) storing in a random access store indications of the position and size of each viewport area, together with an indication of the priority level of the viewport area, b) constructing a first matrix of (2n+1)2 elements, where n is equal to the number of viewport areas, by assigning a vertical component to each vertical coordinate of each viewport area and a horizontal component to each horizontal coordinate of each viewport area, and for each element so formed storing an indication of the highest priority level of the viewports falling within the boundary formed by the coordinates defining the element, c) receiving an indication that the display of a particular viewport is to be changed, d) constructing a second matrix for the viewport area, the display of which is to be changed, by storing, for each element, an indication whether or not a portion of the particular viewport, that is to be changed, falls within its boundary and associating the corresponding elements of identical rows and columns together, e) receiving indications of the coordinate values of the display to be displayed in the viewport area, f) using the condensed matrix to determine the coordinates of the received display information that can be displayed in the viewport area, and g) storing the indications of the coordinate values in the random access store. The apparatus includes a communications processor and a procedure processor arranged to be controlled to perform the method.