lib/connectionpoint.c

   1 /* Dia -- an diagram creation/manipulation program
   2  * Copyright (C) 1998 Alexander Larsson
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License as published by
   6  * the Free Software Foundation; either version 2 of the License, or
   7  * (at your option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, write to the Free Software
  16  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  17  */
  18
  19 #include "config.h"
  20 #include "connectionpoint.h"
  21
  22 /* Returns the available directions on a slope.
  23  * The right-hand side of the line is assumed to be within the object,
  24  * and thus not available. */
  25 gint
  26 find_slope_directions(Point from, Point to)
  27 {
  28   gint dirs;
  29   gint slope;
  30
  31   if (fabs(from.y-to.y) < 0.0000001)
  32     return (from.x > to.x?DIR_SOUTH:DIR_NORTH);
  33   if (fabs(from.x-to.x) < 0.0000001)
  34     return (from.y > to.y?DIR_WEST:DIR_EAST);
  35
  36   point_sub(&to, &from);
  37   slope = fabs(to.y/to.x);
  38
  39   dirs = 0;
  40   if (slope < 2) { /* Flat enough to allow north-south */
  41     if (to.x > 0) { /* The outside is north, not south */
  42       dirs |= DIR_NORTH;
  43     } else {
  44       dirs |= DIR_SOUTH;
  45     }
  46   }
  47   if (slope > .5) { /* Steep enough to allow east-west */
  48     if (to.y > 0) {  /* The outside is east, not west */
  49       dirs |= DIR_EAST;
  50     } else {
  51       dirs |= DIR_WEST;
  52     }
  53   }
  54   return dirs;
  55 }
  56
  57
  58 /** Update the object-settable parts of a connectionpoints.
  59  * p: A ConnectionPoint pointer (non-NULL).
  60  * x: The x coordinate of the connectionpoint.
  61  * y: The y coordinate of the connectionpoint.
  62  * dirs: The directions that are open for connections on this point.
  63  */
  64 void
  65 connpoint_update(ConnectionPoint *p, real x, real y, gint dirs)
  66 {
  67   p->pos.x = x;
  68   p->pos.y = y;
  69   p->directions = dirs;
  70 }
  71
  72 /** Returns TRUE if the given connection point is non-null and autogapped.
  73  */
  74 gboolean
  75 connpoint_is_autogap(ConnectionPoint *cp) {
  76   return cp != NULL && (cp->flags & CP_FLAG_AUTOGAP);
  77 }