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RECTANGLE(3GC)        AVIATOR GRAPHICS INTERFACE CLASSES         RECTANGLE(3GC)



NAME
        FB_CLASS__RECTANGLE_2DS_OVERLAPPING,
        FB_CLASS__RECTANGLE_2DS_NONOVERLAPPING - 2D screen rectangle classes

SYNOPSIS
        #include <agi.h>
        register Fbuffer fbp;

        fbstart(fbp, FB_CLASS__RECTANGLE_2DS_OVERLAPPING)  {
        }  fbend(fbp);

        fbstart(fbp, FB_CLASS__RECTANGLE_2DS_NONOVERLAPPING)  {
        }  fbend(fbp);

DESCRIPTION
        The class FB_CLASS__RECTANGLE_2DS_OVERLAPPING is used for rendering
        overlapping rectangles and rectangle meshes in two dimensional screen
        coordinates.  The rectangle is aligned to the screen and is defined
        with just two points.  Overlapping rectangles have the characteristic
        that two adjacent rectangles using the same two points will overlap by
        exactly a line.  If two adjacent rectangles are rendered with the
        exclusive-OR raster operation, a line connecting the two points in
        common will be the original image.

        The class FB_CLASS__RECTANGLE_2DS_NONOVERLAPPING is used for rendering
        nonoverlapping rectangles and rectangle meshes in two dimensional
        screen coordinates.  The rectangle is aligned to the screen and is
        defined with just two points.  Nonoverlapping rectangles have the
        characteristic that two adjacent rectangles using the same two points
        will have no pixels in common.

MEMBERS
        The following public members can be accessed by using routines
        fbput(3G) and fbget(3G).  These 32 bit numbers can be signed integer,
        signed 16.16 fixed point, or IEEE single precision floating point
        format.  The coordinate (0,0) is the upper left corner of the paint
        canvas, or the upper left corner of the frame buffer when running
        without a windowing system.

        FB_MEMBER__X__INTEGER
        FB_MEMBER__X__FIXED
        FB_MEMBER__X__FLOAT
                X is the horizontal location of the end point of the rectangle
                currently being defined.
        FB_MEMBER__Y__INTEGER
        FB_MEMBER__Y__FIXED
        FB_MEMBER__Y__FLOAT
                Y is the vertical location of the end point of the rectangle
                currently being defined.

FUNCTIONS
        The following public functions can be called by using the fbcall(3G)
        routine:

        FB_FUNCTION__STORE_INCREMENT
                The STORE function stores the current point (X and Y) into the
                frame buffer.  The point reference is then incremented to
                reference the next point on the rectangle.
        FB_FUNCTION__RENDER
                The RENDER function causes the frame buffer to render the
                rectangle.

SEE ALSO
        fbcall(3G), fbend(3G), fbget(3G), fbput(3G), fbstart(3G)

PERFORMANCE
        INTEGER is the fastest format.

        When rendering only few rectangles, RECTANGLE_2DS_OVERLAPPING has
        less overhead (startup and cleanup costs).  Try to use
        RECTANGLE_2DS_OVERLAPPING instead of RECTANGLE_2DS_NONOVERLAPPING
        when clearing a window or drawing a large polygon.



AGI Release 1.8         Last change: 25 December 1991