Importance

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Abstract

A method and apparatus for managing background and foreground display images. Graphics memory for images which are rendered in software is referenced by a processor using an MMU (memory mapping unit) having MMU tables. The graphics memory includes a portion for on-screen display, and a portion which can be written into but which is not displayed. When a background image is overlaid by a foreground image, the portion of the background image overlaid is copied to a save-away area, and the MMU tables are altered so that software rendering of the background image automatically occurs in the save-away area. However, the foreground image is written directly into the on-screen display area by rendering hardware. This allows the software-rendered image to be kept up to date, and allows data for the software-rendered image not to be lost during the time the background image is covered up. When the background image is no longer overlaid by the foreground image, the portion of the background image which was overlaid is copied back from the save-away area to the on-screen display area. The MMU tables are altered so that software rendering of the background image thereafter automatically occurs in the on-screen display area This allows the software-rendered image to be quickly displayed on screen in its updated form.

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First Claim