A cursor generation circuit for an image display system that includes a storing circuit for storing image data. The storing circuit includes a first port to provide access to the image data to the display system and a second port to provide access to the image data to a display device for displaying the image data. A combining circuit is further provided to combine the image data with cursor data in the storing circuit when the storing circuit is being accessed by the display device. However, the combining circuit removes the cursor data from the image data when the image data is being accessed by the display system through the first port.
A raster scanned video display for high resolution graphics on to which a graphical cursor can be superimposed. Cursor data corresponding to the next raster line of the image is read out of a data store during the line blanking interval and stored in a fast memory. During scanning of that next raster line the cursor data is combined with the image data. By combining the cursor data with the image data in this way, on a line-by-line basis, storage space requirements in the fast memory are greatly reduced.
A system for using the page buffer memory which stores the pixel map to generate the cursor in a CRT display. An unused portion of the memory is used to store a duplicate copy of the band in which the cursor is currently located, and the cursor is written into its appropriate location in this duplicate band, thus destroying the underlying image in the duplicate, but not in the original. The display is then generated by cycling through the page buffer except that the duplicate band containing the cursor, instead of the original band containing the underlying image, is displayed. After each display is generated, during the time when the scan returns from the bottom to the top of the display, if the cursor has moved since the previous display, the new band containing the cursor is created in the unused portion, and the display process is repeated.
In a data processing apparatus including a single delete key, in accordance with a cursor position when the delete key is operated, a selection is made as to whether to execute a so-called "delete function" where the data indicated by the cursor is deleted, or a so-called "back delete function" where the data just before the cursor-indicated data is deleted. When the cursor indicates the data subsequent to the end data, the back delete function is executed. In other cases, the delete function is executed.
A cursor display control in a graphic display system is provided in which a storage range is provided for exclusive use for a cursor pattern and a desired shape is defined in the storage range to thereby perform a high-speed cursor movement. A display control apparatus in the graphic display system includes a memory for storing a cursor pattern, shift register for performing a shift processing in a non-display period of the cursor for positioning in the display screen, and parallel-serial converter for performing parallel to serial conversion at the display timing of the cursor, whereby the apparatus is suitable to be integrated in the form of an LSI and the cursor can be moved at a high speed on the screen.
Display data is stored in a display memory in densely packed format in all display modes under control of memory controller logic which modifies original addresses for mapping display data into the display memory such that a stream of data for driving a display device can be generated from sequential memory locations. This enables the display memory to take advantage of the benefits of dual-ported memory technology whilst maintaining compatibility with VGA display modes. In order to provide complete VGA compatibility, even in unusual applications, a duplicate auxiliary display memory for the storage of the display data in accordance with the original addresses can be provided. This auxiliary display memory is not used for updating the display, but solely for the retrieval of the display data.
