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Smooth Scrolling of Scrollable Panel Area Data On a Non-Programmable Workstation

IP.com Disclosure Number: IPCOM000120570D
Original Publication Date: 1991-May-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 3 page(s) / 141K

Publishing Venue

IBM

Related People

Eagen, ST: AUTHOR [+2]

Abstract

A Work Station Controller (WSC) provides attachment of multiple Non- Programmable Terminals (NPTs) to a host computer system. WSCs may support smooth scrolling of a file or other data on a NPT display screen by storing the entire file in WSC memory and allowing the cursor movement keys to smooth scroll the file data. However, WSC memory is limited and the WSC may not be able to store an entire large file. This article describes a display data stream handshaking method between a WSC and host processor, such that the entire file appears (from the user's view) to be entirely stored in WSC memory.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 45% of the total text.

Smooth Scrolling of Scrollable Panel Area Data On a Non-Programmable
Workstation

      A Work Station Controller (WSC) provides attachment of
multiple Non- Programmable Terminals (NPTs) to a host computer
system.  WSCs may support smooth scrolling of a file or other data on
a NPT display screen by storing the entire file in WSC memory and
allowing the cursor movement keys to smooth scroll the file data.
However, WSC memory is limited and the WSC may not be able to store
an entire large file.  This article describes a display data stream
handshaking method between a WSC and host processor, such that the
entire file appears (from the user's view) to be entirely stored in
WSC memory.

      The flow of a display data stream between a host processor and
a WSC, and NPT commands between a WSC and an NPT is shown in the
figure.

      An outbound display data stream (host to WSC) typically defines
a screen image, and entry field locations and sizes for an NPT.  The
outbound data stream may also contain smooth scrolling data beyond
what is actually displayed.  An inbound display data stream typically
identifies the keystroke which caused the inbound data stream and any
modified entry field data.  The WSC communicates with the NPT by
sending commands (for example, write to screen, read from screen,
move the cursor, or move screen data).  The NPT communicates with the
WSC by sending user keystrokes.

      This article describes a display data stream handshaking method
between a WSC and host processor, such that an entire large file
appears (from the user's view) to be entirely stored in WSC memory.
The host always knows what portion of the data file is contained in
WSC memory. Output data streams indicate if additional scrollable
data exists beyond what was downloaded to the WSC.  The WSC then
monitors all user keystrokes within the scrollable panel area.  When
the cursor approaches a boundary of scrollable data in WSC memory and
additional data exists in that direction, the WSC sends a request to
the host for additional data in that direction and frees a portion of
stored data from the opposite direction.

      The threshold at which the WSC requests additional data, the
amount of scrollable data initially sent to the WSC, and minimum WSC
memory required per NPT can be determined by defining the following:
     The number of rows or columns involved in scrolling.
     The maximum keystroking rate of the NPT.
     A response time threshold, where the majority of WSC
     requests for additional data will be processed in less
     than the threshold time.  Note:  increasing the
     response time threshold will reduce the chance of
     overrun, but WSC memory requirements will increase.

      In order to simplify the rest of this disclosure, the following
assumptions are used:
     Vertical scrolling only will be assumed, on 80 columns
     of data.
     A maximum NPT keystro...