| 摘要 |
An apparatus for implementing, in hardware, clipping and intercoordinate comparison logic in a graphic display subsystem. Clipping is necessary when an object to be displayed is defined as being only partially contained within a pre-determined window on a video display. For example, if a rectangular window is defined in the upper left hand corner of a video display, and a line has been defined which extends from the upper left-hand corner to the lower right-hand corner of the display, the portion of the line which is outside the defined window is not displayed, i.e., it is clipped. Additionally, if a line of text is wider than the window, the portion of the line of text which is outside the window must also be clipped. Calculations in the nature of comparisons are performed in hardware for use by a graphical subsystem for clipping images to be displayed on a video display in hardware whenever possible, leaving for software only those images, or portions of images which cannot be reliably clipped using the hardware of the graphical subsystem. |
