Browse Prior Art Database

Hardware Control of Display Screen Windowing

IP.com Disclosure Number: IPCOM000059906D
Original Publication Date: 1986-Feb-01
Included in the Prior Art Database: 2005-Mar-08
Document File: 3 page(s) / 66K

Publishing Venue

IBM

Related People

Platt, M: AUTHOR [+2]

Abstract

In a graphics display, the screen is divided into a number of windows to display sections of multiple applications. Each window has a smaller viewport, and may be moved around under the viewport by cursor control. Hardware controls the position of the window on the screen so that the cursor lies within the viewport. This is achieved by dividing the display screen into four logical areas around the viewport and detecting when the cursor occurs within one of these areas. If it does, the start of the window is adjusted. Also, the final position of the cursor is controlled by an algorithm to position the cursor at the most logical position within the viewport. The use of multiple windows on a display screen to display sections of multiple applications is becoming increasingly prevalent.

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Hardware Control of Display Screen Windowing

In a graphics display, the screen is divided into a number of windows to display sections of multiple applications. Each window has a smaller viewport, and may be moved around under the viewport by cursor control. Hardware controls the position of the window on the screen so that the cursor lies within the viewport. This is achieved by dividing the display screen into four logical areas around the viewport and detecting when the cursor occurs within one of these areas. If it does, the start of the window is adjusted. Also, the final position of the cursor is controlled by an algorithm to position the cursor at the most logical position within the viewport. The use of multiple windows on a display screen to display sections of multiple applications is becoming increasingly prevalent. Typically, a display screen will be divided up into multiple viewports which are smaller than the application window and display a portion of the complete application window through the viewport (Fig. 1). The application window may be moved around under the viewport to display the area of interest in the viewport. This area is usually indicated by a cursor position, and so the display has a microprocessor which calculates in code whether the cursor is visible in the viewport, and if the cursor is not visible, the code moves the window position to make the cursor appear in the viewport. This code has to be executed for every cursor move, and so causes a large amount of processing to be executed for each cursor move, with corresponding degradation in the performance of the display terminal. In this disclosure the position of the window on the display screen is controlled by hardware depending on the position of the cursor; this improves the performance of the display terminal by removing the need for code to be executed each time the cursor is moved. In addition, the logic described implements an algorithm which positions the window in such a way as to leave the cursor at the most logical position in the viewport. Hardware implementation of the viewport is by using an escape character or attribute in the display screen buffer to indicate which application window is to be displayed in the viewport, and t...