LCOV - app.info - gfx/cairo/cairo/src/cairo-slope.c

LCOV - code coverage report
| Current view: | directory - gfx/cairo/cairo/src - cairo-slope.c (source / functions) |  | Found | Hit | Coverage |
| Test: | app.info | Lines: | 17 | 0 | 0.0 %
| Date: | 2012-07-07 | Functions: | 1 | 0 | 0.0 %

           1                 : /* cairo - a vector graphics library with display and print output
           2                 :  *
           3                 :  * Copyright © 2002 University of Southern California
           4                 :  *
           5                 :  * This library is free software; you can redistribute it and/or
           6                 :  * modify it either under the terms of the GNU Lesser General Public
           7                 :  * License version 2.1 as published by the Free Software Foundation
           8                 :  * (the "LGPL") or, at your option, under the terms of the Mozilla
           9                 :  * Public License Version 1.1 (the "MPL"). If you do not alter this
          10                 :  * notice, a recipient may use your version of this file under either
          11                 :  * the MPL or the LGPL.
          12                 :  *
          13                 :  * You should have received a copy of the LGPL along with this library
          14                 :  * in the file COPYING-LGPL-2.1; if not, write to the Free Software
          15                 :  * Foundation, Inc., 51 Franklin Street, Suite 500, Boston, MA 02110-1335, USA
          16                 :  * You should have received a copy of the MPL along with this library
          17                 :  * in the file COPYING-MPL-1.1
          18                 :  *
          19                 :  * The contents of this file are subject to the Mozilla Public License
          20                 :  * Version 1.1 (the "License"); you may not use this file except in
          21                 :  * compliance with the License. You may obtain a copy of the License at
          22                 :  * http://www.mozilla.org/MPL/
          23                 :  *
          24                 :  * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY
          25                 :  * OF ANY KIND, either express or implied. See the LGPL or the MPL for
          26                 :  * the specific language governing rights and limitations.
          27                 :  *
          28                 :  * The Original Code is the cairo graphics library.
          29                 :  *
          30                 :  * The Initial Developer of the Original Code is University of Southern
          31                 :  * California.
          32                 :  *
          33                 :  * Contributor(s):
          34                 :  *      Carl D. Worth <cworth@cworth.org>
          35                 :  */
          36                 :
          37                 : #include "cairoint.h"
          38                 :
          39                 : #include "cairo-slope-private.h"
          40                 :
          41                 : /* Compare two slopes. Slope angles begin at 0 in the direction of the
          42                 :    positive X axis and increase in the direction of the positive Y
          43                 :    axis.
          44                 :
          45                 :    This function always compares the slope vectors based on the
          46                 :    smaller angular difference between them, (that is based on an
          47                 :    angular difference that is strictly less than pi). To break ties
          48                 :    when comparing slope vectors with an angular difference of exactly
          49                 :    pi, the vector with a positive dx (or positive dy if dx's are zero)
          50                 :    is considered to be more positive than the other.
          51                 :
          52                 :    Also, all slope vectors with both dx==0 and dy==0 are considered
          53                 :    equal and more positive than any non-zero vector.
          54                 :
          55                 :    <  0 => a less positive than b
          56                 :    == 0 => a equal to b
          57                 :    >  0 => a more positive than b
          58                 : */
          59                 : int
          60               0 : _cairo_slope_compare (const cairo_slope_t *a, const cairo_slope_t *b)
          61                 : {
          62               0 :     cairo_int64_t ady_bdx = _cairo_int32x32_64_mul (a->dy, b->dx);
          63               0 :     cairo_int64_t bdy_adx = _cairo_int32x32_64_mul (b->dy, a->dx);
          64                 :     int cmp;
          65                 :
          66               0 :     cmp = _cairo_int64_cmp (ady_bdx, bdy_adx);
          67               0 :     if (cmp)
          68               0 :         return cmp;
          69                 :
          70                 :     /* special-case zero vectors.  the intended logic here is:
          71                 :      * zero vectors all compare equal, and more positive than any
          72                 :      * non-zero vector.
          73                 :      */
          74               0 :     if (a->dx == 0 && a->dy == 0 && b->dx == 0 && b->dy ==0)
          75               0 :         return 0;
          76               0 :     if (a->dx == 0 && a->dy == 0)
          77               0 :         return 1;
          78               0 :     if (b->dx == 0 && b->dy ==0)
          79               0 :         return -1;
          80                 :
          81                 :     /* Finally, we're looking at two vectors that are either equal or
          82                 :      * that differ by exactly pi. We can identify the "differ by pi"
          83                 :      * case by looking for a change in sign in either dx or dy between
          84                 :      * a and b.
          85                 :      *
          86                 :      * And in these cases, we eliminate the ambiguity by reducing the angle
          87                 :      * of b by an infinitesimally small amount, (that is, 'a' will
          88                 :      * always be considered less than 'b').
          89                 :      */
          90               0 :     if ((a->dx ^ b->dx) < 0 || (a->dy ^ b->dy) < 0) {
          91               0 :         if (a->dx > 0 || (a->dx == 0 && a->dy > 0))
          92               0 :             return +1;
          93                 :         else
          94               0 :             return -1;
          95                 :     }
          96                 :
          97                 :     /* Finally, for identical slopes, we obviously return 0. */
          98               0 :     return 0;
          99                 : }

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