Browse Prior Art Database

Graphics Multiple Viewports

IP.com Disclosure Number: IPCOM000038664D
Original Publication Date: 1987-Feb-01
Included in the Prior Art Database: 2005-Jan-31
Document File: 2 page(s) / 40K

Publishing Venue

IBM

Related People

Easton, CJ: AUTHOR

Abstract

Given a graphics display system having overlapping viewports with different priority levels, with picture data for each viewport, and a correspondence between viewports and character cells: An attribute bit with each character cell indicates those areas of a viewport which are overlapped by another viewport of higher priority. The attribute bits are used to inhibit overlapped viewport areas when the picture data is written to the bit planes. This arrangement is restricted to a display having a hardware character cell refresh buffer and to viewports restricted to character cell boundaries. Fig. 1 shows a screen 1 with viewport A having higher priority than viewport B. Thus, viewport A is fully displayed while area 2 of viewport B is not displayed.

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Graphics Multiple Viewports

Given a graphics display system having overlapping viewports with different priority levels, with picture data for each viewport, and a correspondence between viewports and character cells: An attribute bit with each character cell indicates those areas of a viewport which are overlapped by another viewport of higher priority. The attribute bits are used to inhibit overlapped viewport areas when the picture data is written to the bit planes. This arrangement is restricted to a display having a hardware character cell refresh buffer and to viewports restricted to character cell boundaries. Fig. 1 shows a screen 1 with viewport A having higher priority than viewport B. Thus, viewport A is fully displayed while area 2 of viewport B is not displayed. This is sometimes known as a messy desk concept in which multiple viewports overlap. European Patent Application 0145817 describes a system with multiple viewports which may overlap. In order to write low priority viewports without disturbing data displayed in those of a higher priority, a mask buffer is used to prevent overwriting of high priority viewports. Fig. 2 illustrates a graphics multiple viewport display system. The viewport boundaries are restricted to character cell boundaries. The picture data formatter sets up character cells together with attributes in the refresh buffer - for example, color attributes. To control overlapping viewports, an additional attribute bit for character...