Browse Prior Art Database

Graphical List Scrolling

IP.com Disclosure Number: IPCOM000034780D
Original Publication Date: 1989-Apr-01
Included in the Prior Art Database: 2005-Jan-27
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Franklin, SM: AUTHOR [+2]

Abstract

This article describes a method for efficiently scrolling a graphical list in the OS/2 Presentation Manager environment. An application may wish to present a list of objects in a graphical format, drawing a picture to represent each item in the list. Often, the size of the application's window does not permit all items in the list to be visible to the user. As the user scrolls through the list, the new items must be drawn in the window. As graphical objects increase in complexity, the scrolling of these objects slows considerably. However, if all graphical objects can be drawn in a virtual window upon list initialization, scrolling efficiency increases considerably. Efficient scrolling of graphical lists may be achieved in the following manner.

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Graphical List Scrolling

This article describes a method for efficiently scrolling a graphical list in the OS/2 Presentation Manager environment. An application may wish to present a list of objects in a graphical format, drawing a picture to represent each item in the list. Often, the size of the application's window does not permit all items in the list to be visible to the user. As the user scrolls through the list, the new items must be drawn in the window. As graphical objects increase in complexity, the scrolling of these objects slows considerably. However, if all graphical objects can be drawn in a virtual window upon list initialization, scrolling efficiency increases considerably. Efficient scrolling of graphical lists may be achieved in the following manner. When a list facility is initialized, all of the graphical objects are drawn into a virtual window. The size of the visible window is used to calculate the appropriate viewport on the window. As the user scrolls the window, the viewport on the virtual list window is changed to reflect the scrolling. Since all of the actual drawing has already occurred in the virtual window, the scrolling occurs with a significant increase in speed.

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