Abstract: A computer system includes a display controller which supports video display. The display controller includes circuitry for determining which portions of one or more video windows should be written to the frame buffer responsive to the locations of other screen objects which may overlie the video window on the display. An unused portion of frame buffer memory is used to stored a plurality of transition groups, each group defining which portions of the video window are visible within a range of scanlines. The transition information is used by clipped circuitry to enable or disable writing of video information to the frame buffer.

Abstract: A display controller includes a text engine which stores font information, including image and width information, in a unused portion of the frame buffer. A character string comprising width vectors and indices which point to the characters to be drawn, is passed to the display controller from the driver software. Once the character string is received, the text engine draws the indicated characters by reference to the font information previously stored in the character information memory by the driver, allowing the operating system to continue operations while the text string is being drawn to the viewport of the frame buffer.

Abstract: A method and system for accommodating multiple video controllers. The method includes communicating a plurality of primitive commands to a video controller having a configuration of a predetermined type. Further, the method includes electronically determining the type of the configuration, and generating a vector table comprising a plurality of device-specific routines. Each entry in the vector table may point to a device-specific routine for hardware acceleration of a primitive command or to a default routine which sets the video controller in a specific mode which can be operated by a set of colordepth-specific routines which operate on any video controller set to the specific mode. In response to a primitive from the operating environment, common code, which is device and colordepth independent, will access a routine via the vector table. If the vector table does not access a hardware accelerated routine, colordepth specific code is used to execute the primitive.