xenocara/xserver/fb/fbtrap.c

/*
 * Copyright © 2004 Keith Packard
 *
 * Permission to use, copy, modify, distribute, and sell this software and its
 * documentation for any purpose is hereby granted without fee, provided that
 * the above copyright notice appear in all copies and that both that
 * copyright notice and this permission notice appear in supporting
 * documentation, and that the name of Keith Packard not be used in
 * advertising or publicity pertaining to distribution of the software without
 * specific, written prior permission.  Keith Packard makes no
 * representations about the suitability of this software for any purpose.  It
 * is provided "as is" without express or implied warranty.
 *
 * KEITH PACKARD DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
 * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
 * EVENT SHALL KEITH PACKARD BE LIABLE FOR ANY SPECIAL, INDIRECT OR
 * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
 * DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
 * TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
 * PERFORMANCE OF THIS SOFTWARE.
 */

#ifdef HAVE_DIX_CONFIG_H
#include <dix-config.h>
#endif

#include "fb.h"

#include "picturestr.h"
#include "mipict.h"
#include "renderedge.h"
#include "fbpict.h"

void
fbAddTraps (PicturePtr	pPicture,
	    INT16	x_off,
	    INT16	y_off,
	    int		ntrap,
	    xTrap	*traps)
{
    int image_xoff, image_yoff;
    pixman_image_t *image = image_from_pict (pPicture, FALSE, &image_xoff, &image_yoff);

    if (!image)
	return;
    
    pixman_add_traps (image, x_off, y_off, ntrap, (pixman_trap_t *)traps);

    free_pixman_pict (pPicture, image);
}

void
fbRasterizeTrapezoid (PicturePtr    pPicture,
		      xTrapezoid  *trap,
		      int	    x_off,
		      int	    y_off)
{
    int	mask_xoff, mask_yoff;
    pixman_image_t *image = image_from_pict (pPicture, FALSE, &mask_xoff, &mask_yoff);

    if (!image)
	return;

    pixman_rasterize_trapezoid (image, (pixman_trapezoid_t *)trap, x_off, y_off);

    free_pixman_pict (pPicture, image);
}

static int
_GreaterY (xPointFixed *a, xPointFixed *b)
{
    if (a->y == b->y)
	return a->x > b->x;
    return a->y > b->y;
}

/*
 * Note that the definition of this function is a bit odd because
 * of the X coordinate space (y increasing downwards).
 */
static int
_Clockwise (xPointFixed *ref, xPointFixed *a, xPointFixed *b)
{
    xPointFixed	ad, bd;

    ad.x = a->x - ref->x;
    ad.y = a->y - ref->y;
    bd.x = b->x - ref->x;
    bd.y = b->y - ref->y;

    return ((xFixed_32_32) bd.y * ad.x - (xFixed_32_32) ad.y * bd.x) < 0;
}

/* FIXME -- this could be made more efficient */
void
fbAddTriangles (PicturePtr  pPicture,
		INT16	    x_off,
		INT16	    y_off,
		int	    ntri,
		xTriangle *tris)
{
    xPointFixed	  *top, *left, *right, *tmp;
    xTrapezoid	    trap;

    for (; ntri; ntri--, tris++)
    {
	top = &tris->p1;
	left = &tris->p2;
	right = &tris->p3;
	if (_GreaterY (top, left)) {
	    tmp = left; left = top; top = tmp;
	}
	if (_GreaterY (top, right)) {
	    tmp = right; right = top; top = tmp;
	}
	if (_Clockwise (top, right, left)) {
	    tmp = right; right = left; left = tmp;
	}
	
	/*
	 * Two cases:
	 *
	 *		+		+
	 *	       / \             / \
	 *	      /   \           /   \
	 *	     /     +         +     \
	 *      /    --           --    \
	 *     /   --               --   \
	 *    / ---                   --- \
	 *	 +--                         --+
	 */
	
	trap.top = top->y;
	trap.left.p1 = *top;
	trap.left.p2 = *left;
	trap.right.p1 = *top;
	trap.right.p2 = *right;
	if (right->y < left->y)
	    trap.bottom = right->y;
	else
	    trap.bottom = left->y;
	fbRasterizeTrapezoid (pPicture, &trap, x_off, y_off);
	if (right->y < left->y)
	{
	    trap.top = right->y;
	    trap.bottom = left->y;
	    trap.right.p1 = *right;
	    trap.right.p2 = *left;
	}
	else
	{
	    trap.top = left->y;
	    trap.bottom = right->y;
	    trap.left.p1 = *left;
	    trap.left.p2 = *right;
	}
	fbRasterizeTrapezoid (pPicture, &trap, x_off, y_off);
    }
}