/*

 *

 * Copyright © 2000 Keith Packard, member of The XFree86 Project, Inc.

 *             2005 Lars Knoll & Zack Rusin, Trolltech

 *

 * 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.

 *

 * THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS

 * SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND

 * FITNESS, IN NO EVENT SHALL THE COPYRIGHT HOLDERS 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_CONFIG_H

#include <config.h>

#endif

#include "pixman-private.h"

void

_pixman_gradient_walker_init (pixman_gradient_walker_t *walker,

                              gradient_t *              gradient,

                              pixman_repeat_t   repeat)

{

    walker->num_stops = gradient->n_stops;

    walker->stops     = gradient->stops;

    walker->left_x    = 0;

    walker->right_x   = 0x10000;

    walker->stepper   = 0;

    walker->left_ag   = 0;

    walker->left_rb   = 0;

    walker->right_ag  = 0;

    walker->right_rb  = 0;

    walker->repeat    = repeat;

    walker->need_reset = TRUE;

}

static void

gradient_walker_reset (pixman_gradient_walker_t *walker,

           pixman_fixed_48_16_t      pos)

{

    int32_t x, left_x, right_x;

    pixman_color_t *left_c, *right_c;

    int n, count = walker->num_stops;

    pixman_gradient_stop_t *stops = walker->stops;

    if (walker->repeat == PIXMAN_REPEAT_NORMAL)

    {

  x = (int32_t)pos & 0xffff;

    }

    else if (walker->repeat == PIXMAN_REPEAT_REFLECT)

    {

  x = (int32_t)pos & 0xffff;

  if ((int32_t)pos & 0x10000)

      x = 0x10000 - x;

    }

    else

    {

  x = pos;

    }

    for (n = 0; n < count; n++)

    {

  if (x < stops[n].x)

      break;

    }

    left_x =  stops[n - 1].x;

    left_c = &stops[n - 1].color;

    right_x =  stops[n].x;

    right_c = &stops[n].color;

    if (walker->repeat == PIXMAN_REPEAT_NORMAL)

    {

  left_x  += (pos - x);

  right_x += (pos - x);

    }

    else if (walker->repeat == PIXMAN_REPEAT_REFLECT)

    {

  if ((int32_t)pos & 0x10000)

  {

      pixman_color_t  *tmp_c;

      int32_t tmp_x;

      tmp_x   = 0x10000 - right_x;

      right_x = 0x10000 - left_x;

      left_x  = tmp_x;

      tmp_c   = right_c;

      right_c = left_c;

      left_c  = tmp_c;

      x = 0x10000 - x;

  }

  left_x  += (pos - x);

  right_x += (pos - x);

    }

    else if (walker->repeat == PIXMAN_REPEAT_NONE)

    {

  if (n == 0)

      right_c = left_c;

  else if (n == count)

      left_c = right_c;

    }

    walker->left_x   = left_x;

    walker->right_x  = right_x;

    walker->left_ag  = ((left_c->alpha >> 8) << 16)   | (left_c->green >> 8);

    walker->left_rb  = ((left_c->red & 0xff00) << 8)  | (left_c->blue >> 8);

    walker->right_ag = ((right_c->alpha >> 8) << 16)  | (right_c->green >> 8);

    walker->right_rb = ((right_c->red & 0xff00) << 8) | (right_c->blue >> 8);

    if (walker->left_x == walker->right_x                ||

        (walker->left_ag == walker->right_ag &&

   walker->left_rb == walker->right_rb))

    {

  walker->stepper = 0;

    }

    else

    {

  int32_t width = right_x - left_x;

  walker->stepper = ((1 << 24) + width / 2) / width;

    }

    walker->need_reset = FALSE;

}

uint32_t

_pixman_gradient_walker_pixel (pixman_gradient_walker_t *walker,

                               pixman_fixed_48_16_t      x)

{

    int dist, idist;

    uint32_t t1, t2, a, color;

    if (walker->need_reset || x < walker->left_x || x >= walker->right_x)

  gradient_walker_reset (walker, x);

    dist  = ((int)(x - walker->left_x) * walker->stepper) >> 16;

    idist = 256 - dist;

    /* combined INTERPOLATE and premultiply */

    t1 = walker->left_rb * idist + walker->right_rb * dist;

    t1 = (t1 >> 8) & 0xff00ff;

    t2  = walker->left_ag * idist + walker->right_ag * dist;

    t2 &= 0xff00ff00;

    color = t2 & 0xff000000;

    a     = t2 >> 24;

    t1  = t1 * a + 0x800080;

    t1  = (t1 + ((t1 >> 8) & 0xff00ff)) >> 8;

    t2  = (t2 >> 8) * a + 0x800080;

    t2  = (t2 + ((t2 >> 8) & 0xff00ff));

    return (color | (t1 & 0xff00ff) | (t2 & 0xff00));

}