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Cursor Display on Raster Graphic Devices

IP.com Disclosure Number: IPCOM000042088D
Original Publication Date: 1984-Mar-01
Included in the Prior Art Database: 2005-Feb-03
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Gay, AC: AUTHOR

Abstract

In general, cross-hair, rectangular (or other) cursors are drawn on single buffered raster displays by operating on bits in the bit plane(s) using one of the following functions: . XOR cursor bits with bit plane(s) . OR (set) cursor bits with bit plane(s), i.e., 'all 1's' cursor . AND NOT (reset) cursor bits with bit plane(s), i.e., 'all d's cursor When the cursor is deleted and/or moved, the pels (picture elements) of the picture in the bit planes must be restored. Currently there are two alternatives: 1. Re-draw the picture 2. Save the bits in the cursor positions before drawing the cursor, and restore them when the cursor is deleted. [Note that for the XOR cursor, simply XORing it into the bit plane a second time will restore the picture.

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Cursor Display on Raster Graphic Devices

In general, cross-hair, rectangular (or other) cursors are drawn on single buffered raster displays by operating on bits in the bit plane(s) using one of the following functions: . XOR cursor bits with bit plane(s) . OR (set) cursor bits with bit plane(s), i.e., 'all 1's' cursor . AND NOT (reset) cursor bits with bit plane(s), i.e., 'all d's cursor When the cursor is deleted and/or moved, the pels (picture elements) of the picture in the bit planes must be restored. Currently there are two alternatives: 1. Re-draw the picture 2. Save the bits in the cursor positions before drawing the cursor, and restore them when the cursor is deleted. [Note that for the XOR cursor, simply XORing it into the bit plane a second time will restore the picture. However, the XOR cursor has the disadvantage that during display of the cursor, pels are missing at the intersection points of the cursor and the image.] Obviously, the performance of method (1) is slow, hence method (2) is often used. However, method (2) still takes time and storage space, e.g., 2d48 bits for a cross-hair cursor on a 1024 X 1024 raster display and 128 storage accesses assuming 16-bit words. Some raster displays have a separate, dedicated bit plane for operations such as area fill. On these displays, improved performance can be obtained by drawing the cursor into this plane between area fill or other operations and enabling display of this plane. Thus, no hardware/firm...