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Screen Updating Method

IP.com Disclosure Number: IPCOM000035221D
Original Publication Date: 1989-Jun-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 3 page(s) / 55K

Publishing Venue

IBM

Related People

Ishikawa, S: AUTHOR [+2]

Abstract

This article describes a new screen updating method for multi-media processing systems, such as graphics editors, which display various kinds of objects on an APA (All-Points-Addressable) screen in a WYSIWYG (What You See Is What You Get) manner, and which provide interactive editing operations for moving objects, changing object attributes, sizing, and so on. When these operations are activated by a user, the interactive system has to redraw objects on the screen immediately. It is very important that the screen be updated quickly and not flash uncomfortably. A method is described of screen updating that is efficient for redrawing and comfortable to watch.

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Screen Updating Method

This article describes a new screen updating method for multi-media processing systems, such as graphics editors, which display various kinds of objects on an APA (All-Points-Addressable) screen in a WYSIWYG (What You See Is What You Get) manner, and which provide interactive editing operations for moving objects, changing object attributes, sizing, and so on. When these operations are activated by a user, the interactive system has to redraw objects on the screen immediately. It is very important that the screen be updated quickly and not flash uncomfortably. A method is described of screen updating that is efficient for redrawing and comfortable to watch.

Graphics editing operations, such as move, reshape, and delete, are accompanied by processes that include deleting an old object and drawing a new one at a new position on the screen. A delete operation is implemented simply by drawing the object with the background color. However, this method causes a problem when the deleted object overlaps other objects, because the overlapped objects are broken. A simple solution is to redraw all the objects on the screen, but this takes considerable time.

A more advanced method of redrawing utilizes a clipping function. This is a masking function of graphics drawing, which draws objects only within a specified region. In most cases, the region is a rectangle. This redrawing process consists of the following steps:

(Image Omitted)

1. Fill out the clipping region (rectangle) to be redrawn in the background color.
2. Redraw the objects in the region with clipping.

This method reduces the average redrawing time so easily that many systems have used it. However, it is not very comfortable for a user to watch, since for a moment the region is filled with the background color.

We present a screen updating method that solves these problems. Fig. 1 shows an example of redrawing in a delete operation, using our approach. If a user requests the system to delete a circle C in Fig. 1a, the screen updating steps are: 1. Clear circle C by overwriting it wi...