Browse Prior Art Database

Method for Using a Single Rendering Context On an Adapter With Hardware Clipping While Rendering to Multiple Windows

IP.com Disclosure Number: IPCOM000120916D
Original Publication Date: 1991-Jun-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 1 page(s) / 44K

Publishing Venue

IBM

Related People

Henson, LW: AUTHOR [+4]

Abstract

Disclosed is a method for updating the window origin and clipping parameters in the rendering context of a graphics adapter without doing a context switch on a display adapter that requires a context switch to change these parameters.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 94% of the total text.

Method for Using a Single Rendering Context On an Adapter With Hardware
Clipping While Rendering to Multiple Windows

      Disclosed is a method for updating the window origin and
clipping parameters in the rendering context of a graphics adapter
without doing a context switch on a display adapter that requires a
context switch to change these parameters.

      Hardware clipping and window-to-screen coordinate translation
are done on an adapter that supports context switching.  For an
adapter without this hardware support, the clipping and coordinate
translation are done in software.  The performance penalty paid for
coordinate translation is much less than that paid for clipping.  By
moving the translation into the software, we remove the need to
change the window origin when rendering to a new window on the
screen.  Updating the clipping information is the remaining interface
between the adapter and system.

      The benefits of this algorithm are as follows:
      1. Context switching is unnecessary if a controlling graphics
process renders for its clients.  Substantial amounts of time are
saved while off-loading work onto the adapter.  The balance achieved
by this off-loading allows more of the system time to be used for
computation while keeping the graphics speed at an acceptable level.
      2. Window geometry updates can usually proceed without having
to switch rendering contexts.  Window id's are preserved across the
updates, which ar...