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/*
* $Id$
*
* 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.
*/
#include "renderedge.h"
/*
* Compute the smallest value no less than y which is on a
* grid row
*/
xFixed
RenderSampleCeilY (xFixed y, int n)
{
xFixed f = xFixedFrac(y);
xFixed i = xFixedFloor(y);
f = ((f + Y_FRAC_FIRST(n)) / STEP_Y_SMALL(n)) * STEP_Y_SMALL(n) + Y_FRAC_FIRST(n);
if (f > Y_FRAC_LAST(n))
{
f = Y_FRAC_FIRST(n);
i += xFixed1;
}
return (i | f);
}
#define _div(a,b) ((a) >= 0 ? (a) / (b) : -((-(a) + (b) - 1) / (b)))
/*
* Compute the largest value no greater than y which is on a
* grid row
*/
xFixed
RenderSampleFloorY (xFixed y, int n)
{
xFixed f = xFixedFrac(y);
xFixed i = xFixedFloor (y);
f = _div(f - Y_FRAC_FIRST(n), STEP_Y_SMALL(n)) * STEP_Y_SMALL(n) + Y_FRAC_FIRST(n);
if (f < Y_FRAC_FIRST(n))
{
f = Y_FRAC_LAST(n);
i -= xFixed1;
}
return (i | f);
}
/*
* Step an edge by any amount (including negative values)
*/
void
RenderEdgeStep (RenderEdge *e, int n)
{
xFixed_48_16 ne;
e->x += n * e->stepx;
ne = e->e + n * (xFixed_48_16) e->dx;
if (n >= 0)
{
if (ne > 0)
{
int nx = (ne + e->dy - 1) / e->dy;
e->e = ne - nx * (xFixed_48_16) e->dy;
e->x += nx * e->signdx;
}
}
else
{
if (ne <= -e->dy)
{
int nx = (-ne) / e->dy;
e->e = ne + nx * (xFixed_48_16) e->dy;
e->x -= nx * e->signdx;
}
}
}
/*
* A private routine to initialize the multi-step
* elements of an edge structure
*/
static void
_RenderEdgeMultiInit (RenderEdge *e, int n, xFixed *stepx_p, xFixed *dx_p)
{
xFixed stepx;
xFixed_48_16 ne;
ne = n * (xFixed_48_16) e->dx;
stepx = n * e->stepx;
if (ne > 0)
{
int nx = ne / e->dy;
ne -= nx * e->dy;
stepx += nx * e->signdx;
}
*dx_p = ne;
*stepx_p = stepx;
}
/*
* Initialize one edge structure given the line endpoints and a
* starting y value
*/
void
RenderEdgeInit (RenderEdge *e,
int n,
xFixed y_start,
xFixed x_top,
xFixed y_top,
xFixed x_bot,
xFixed y_bot)
{
xFixed dx, dy;
e->x = x_top;
e->e = 0;
dx = x_bot - x_top;
dy = y_bot - y_top;
e->dy = dy;
if (dy)
{
if (dx >= 0)
{
e->signdx = 1;
e->stepx = dx / dy;
e->dx = dx % dy;
e->e = -dy;
}
else
{
e->signdx = -1;
e->stepx = -(-dx / dy);
e->dx = -dx % dy;
e->e = 0;
}
_RenderEdgeMultiInit (e, STEP_Y_SMALL(n), &e->stepx_small, &e->dx_small);
_RenderEdgeMultiInit (e, STEP_Y_BIG(n), &e->stepx_big, &e->dx_big);
}
RenderEdgeStep (e, y_start - y_top);
}
/*
* Initialize one edge structure given a line, starting y value
* and a pixel offset for the line
*/
void
RenderLineFixedEdgeInit (RenderEdge *e,
int n,
xFixed y,
xLineFixed *line,
int x_off,
int y_off)
{
xFixed x_off_fixed = IntToxFixed(x_off);
xFixed y_off_fixed = IntToxFixed(y_off);
xPointFixed *top, *bot;
if (line->p1.y <= line->p2.y)
{
top = &line->p1;
bot = &line->p2;
}
else
{
top = &line->p2;
bot = &line->p1;
}
RenderEdgeInit (e, n, y,
top->x + x_off_fixed,
top->y + y_off_fixed,
bot->x + x_off_fixed,
bot->y + y_off_fixed);
}
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