TinyX/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)
{
    FbBits *buf;

    int bpp;
    int width;
    int stride;
    int height;
    int pxoff, pyoff;

    xFixed x_off_fixed;
    xFixed y_off_fixed;

    RenderEdge l, r;

    xFixed t, b;

    fbGetDrawable(pPicture->pDrawable, buf, stride, bpp, pxoff, pyoff);

    width = pPicture->pDrawable->width;
    height = pPicture->pDrawable->height;
    x_off += pxoff;
    y_off += pyoff;

    x_off_fixed = IntToxFixed(x_off);
    y_off_fixed = IntToxFixed(y_off);

    while (ntrap--) {
        t = traps->top.y + y_off_fixed;
        if (t < 0)
            t = 0;
        t = RenderSampleCeilY(t, bpp);

        b = traps->bot.y + y_off_fixed;
        if (xFixedToInt(b) >= height)
            b = IntToxFixed(height) - 1;
        b = RenderSampleFloorY(b, bpp);

        if (b >= t) {
            /* initialize edge walkers */
            RenderEdgeInit(&l, bpp, t,
                           traps->top.l + x_off_fixed,
                           traps->top.y + y_off_fixed,
                           traps->bot.l + x_off_fixed,
                           traps->bot.y + y_off_fixed);

            RenderEdgeInit(&r, bpp, t,
                           traps->top.r + x_off_fixed,
                           traps->top.y + y_off_fixed,
                           traps->bot.r + x_off_fixed,
                           traps->bot.y + y_off_fixed);

            fbRasterizeEdges(buf, bpp, width, stride, &l, &r, t, b);
        }
        traps++;
    }
}

void
fbRasterizeTrapezoid(PicturePtr pPicture,
                     xTrapezoid * trap, int x_off, int y_off)
{
    FbBits *buf;

    int bpp;

    int width;

    int stride;

    int height;

    int pxoff, pyoff;

    xFixed x_off_fixed _X_UNUSED;
    xFixed y_off_fixed;

    RenderEdge l, r;

    xFixed t, b;

    fbGetDrawable(pPicture->pDrawable, buf, stride, bpp, pxoff, pyoff);

    width = pPicture->pDrawable->width;
    height = pPicture->pDrawable->height;
    x_off += pxoff;
    y_off += pyoff;

    x_off_fixed = IntToxFixed(x_off);
    y_off_fixed = IntToxFixed(y_off);
    t = trap->top + y_off_fixed;
    if (t < 0)
        t = 0;
    t = RenderSampleCeilY(t, bpp);

    b = trap->bottom + y_off_fixed;
    if (xFixedToInt(b) >= height)
        b = IntToxFixed(height) - 1;
    b = RenderSampleFloorY(b, bpp);

    if (b >= t) {
        /* initialize edge walkers */
        RenderLineFixedEdgeInit(&l, bpp, t, &trap->left, x_off, y_off);
        RenderLineFixedEdgeInit(&r, bpp, t, &trap->right, x_off, y_off);

        fbRasterizeEdges(buf, bpp, width, stride, &l, &r, t, b);
    }
}

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);
    }
}