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Diffstat (limited to 'render/renderedge.c')
| -rw-r--r-- | render/renderedge.c | 197 |
1 files changed, 197 insertions, 0 deletions
diff --git a/render/renderedge.c b/render/renderedge.c new file mode 100644 index 000000000..b84eec14d --- /dev/null +++ b/render/renderedge.c @@ -0,0 +1,197 @@ +/* + * $Id$ + * + * 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); +} + |