A graphic interface device produces a video signal for a display such that
the user may select between landscape and portrait image display modes.
The graphic interface device has a pixel data memory array from which a
video output signal is derived. A primary graphics engine renders graphics
in a landscape orientation in conjunction with a frame buffer. The primary
landscape graphics engine stores rendered graphics to the pixel data
memory array and also copies selected graphics in data blocks within the
frame buffer called surfaces. In order to provide other display modes to
display images in different physical orientations, a mode control is
provided in conjunction with a rotated pixel data array buffer to
facilitate the rendering of portrait oriented graphics by the primary
landscape graphics engine. In addition, to facilitate the efficiency and
speed of rendering portrait oriented graphics, a secondary portrait
graphics engine is provided. To enable the secondary portrait graphics
engine to access the frame buffer directly, a rotated surface buffer is
used by the primary landscape engine to store copies of data written to
the rotated data array buffer in the frame buffer in a portrait
orientation.
