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  * @param from Beginning of the slope line.
  26  * @param to End of the slope line.
  27  * @returns The directions open (@see connectionpoint.h) open on the left-hand
  28  *  side of the slope.
  29  */
  30 gint
  31 find_slope_directions(Point from, Point to)
  32 {
  33   gint dirs;
  34   gint slope;
  35
  36   if (fabs(from.y-to.y) < 0.0000001)
  37     return (from.x > to.x?DIR_SOUTH:DIR_NORTH);
  38   if (fabs(from.x-to.x) < 0.0000001)
  39     return (from.y > to.y?DIR_WEST:DIR_EAST);
  40
  41   point_sub(&to, &from);
  42   slope = fabs(to.y/to.x);
  43
  44   dirs = 0;
  45   if (slope < 2) { /* Flat enough to allow north-south */
  46     if (to.x > 0) { /* The outside is north, not south */
  47       dirs |= DIR_NORTH;
  48     } else {
  49       dirs |= DIR_SOUTH;
  50     }
  51   }
  52   if (slope > .5) { /* Steep enough to allow east-west */
  53     if (to.y > 0) {  /* The outside is east, not west */
  54       dirs |= DIR_EAST;
  55     } else {
  56       dirs |= DIR_WEST;
  57     }
  58   }
  59   return dirs;
  60 }
  61
  62
  63 /** Update the object-settable parts of a connectionpoints.
  64  * @param p A ConnectionPoint pointer (non-NULL).
  65  * @param x The x coordinate of the connectionpoint.
  66  * @param y The y coordinate of the connectionpoint.
  67  * @param dirs The directions that are open for connections on this point.
  68  */
  69 void
  70 connpoint_update(ConnectionPoint *p, real x, real y, gint dirs)
  71 {
  72   p->pos.x = x;
  73   p->pos.y = y;
  74   p->directions = dirs;
  75 }
  76
  77 /** Returns TRUE if the given connection point is non-null and autogapped.
  78  * @param cp A connectionpoint.
  79  * @returns TRUE if the given connection point is non-null and has the
  80  *  CP_FLAG_AUTOGAP flag set (i.e. lines connecting to it should try to end
  81  *  at the border of the object instead of at the connection point.
  82  */
  83 gboolean
  84 connpoint_is_autogap(ConnectionPoint *cp)
  85 {
  86   return cp != NULL && (cp->flags & CP_FLAG_AUTOGAP);
  87 }