Browse Prior Art Database

Screen Flicker Prevention

IP.com Disclosure Number: IPCOM000044317D
Original Publication Date: 1984-Dec-01
Included in the Prior Art Database: 2005-Feb-05
Document File: 2 page(s) / 27K

Publishing Venue

IBM

Related People

Hall, ST: AUTHOR

Abstract

Screen flicker may occur on IBM 3270 family display terminals when using alphanumeric character highlighting due to interlacing. This occurs when an empty screen is built up from the top of the screen. This article describes building the screen in reverse order to avoid flicker. Flicker can be a problem when utilizing the extended highlighting attributes of 3270 family terminals. Any terminal which supports the extended highlighting feature, for example, the IBM 3278, 3279 or 3290, is prone to this problem, which is a distraction and a possible source of eye strain. There are three non-default forms of extended highlighting presently defined: reverse video, underscore and blink. The problem is not encountered with default-extended highlighting.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 52% of the total text.

Page 1 of 2

Screen Flicker Prevention

Screen flicker may occur on IBM 3270 family display terminals when using alphanumeric character highlighting due to interlacing. This occurs when an empty screen is built up from the top of the screen. This article describes building the screen in reverse order to avoid flicker. Flicker can be a problem when utilizing the extended highlighting attributes of 3270 family terminals. Any terminal which supports the extended highlighting feature, for example, the IBM 3278, 3279 or 3290, is prone to this problem, which is a distraction and a possible source of eye strain. There are three non-default forms of extended highlighting presently defined: reverse video, underscore and blink. The problem is not encountered with default-extended highlighting. The flicker is caused by the transient creation of large fields having non-default extended highlighting. This situation occurs when an empty screen is gradually built up from the top of the screen. Any given field is created by defining first the start and then the end of the field. For the short variable time period between these two events, the field will cover an area of the screen much larger than is eventually intended. The effect is to switch reverse video (for example) on and off for a large part of the screen, causing a flicker. There is one flicker for each field with non-default highlighting defined in this way. The solution described here is to (optionally) build the screen definition in reverse order. When this is done, the end of a field is defined before the start, and the non-default highlighting has no opportunity to affect areas of the screen outside of the intended field. The reverse order screen building need only be applied when fields with non-default highlighting are present. Therefore, a method of tracking the presence of such fields is incorporated into the embodiment of the solution, that embodiment being the IBM 3270 family alphanumeric data-stream construction process of the Graphical Data Display Manager...