Browse Prior Art Database

Local Buffer Copy

IP.com Disclosure Number: IPCOM000122439D
Original Publication Date: 1991-Dec-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 2 page(s) / 69K

Publishing Venue

IBM

Related People

Russo, VW: AUTHOR

Abstract

Double frame buffers allow a Display List Processor (DLP) to update an image invisibly and independently from the display of that image on a raster scan display device to allow a smooth transition from one image to another. For example, if buffer A is being used to refresh the display device, the DLP can update the image in buffer B (see Fig. 1). This provides visual acuity when the image is changed.

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Local Buffer Copy

      Double frame buffers allow a Display List Processor (DLP)
to update an image invisibly and independently from the display of
that image on a raster scan display device to allow a smooth
transition from one image to another.  For example, if buffer A is
being used to refresh the display device, the DLP can update the
image in buffer B (see Fig. 1).  This provides visual acuity when the
image is changed.

      One problem which arises with this system is that graphics
application packages often require the complete picture to be drawn
in both frame buffers before allowing interactive dialogue with the
user to begin.  For large, complex images this causes a noticeable
(as much as 3 seconds or more) and irksome delay from the time the
image is displayed from the first buffer until the second buffer is
updated and the user permitted to proceed.

      This article describes a local buffer copy function, as an
alternative to redrawing the image in the second buffer, which
provides significant improvement in performance and user ability.

      Fig. 1 depicts the situation.  Assume buffer A is the
foreground buffer (used to refresh the display device) and buffer B
is the back ground buffer (used by the DLP to update the image).
Under normal operation, the contents of buffer A are selected to be
routed to the display for refresh while buffer B is being used by the
DLP to update the image.

      When the DLP is ready to display the n...