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 /** \file connectionpoint.c ConnectionPoint implmentation */
  20
  21 #include "config.h"
  22 #include "connectionpoint.h"
  23
  24 /** Returns the available directions on a slope.
  25  * The right-hand side of the line is assumed to be within the object,
  26  * and thus not available.
  27  * @param from Beginning of the slope line.
  28  * @param to End of the slope line.
  29  * @returns The directions open (@see connectionpoint.h) open on the left-hand
  30  *  side of the slope.
  31  */
  32 gint
  33 find_slope_directions(Point from, Point to)
  34 {
  35   gint dirs;
  36   gint slope;
  37
  38   if (fabs(from.y-to.y) < 0.0000001)
  39     return (from.x > to.x?DIR_SOUTH:DIR_NORTH);
  40   if (fabs(from.x-to.x) < 0.0000001)
  41     return (from.y > to.y?DIR_WEST:DIR_EAST);
  42
  43   point_sub(&to, &from);
  44   slope = fabs(to.y/to.x);
  45
  46   dirs = 0;
  47   if (slope < 2) { /* Flat enough to allow north-south */
  48     if (to.x > 0) { /* The outside is north, not south */
  49       dirs |= DIR_NORTH;
  50     } else {
  51       dirs |= DIR_SOUTH;
  52     }
  53   }
  54   if (slope > .5) { /* Steep enough to allow east-west */
  55     if (to.y > 0) {  /* The outside is east, not west */
  56       dirs |= DIR_EAST;
  57     } else {
  58       dirs |= DIR_WEST;
  59     }
  60   }
  61   return dirs;
  62 }
  63
  64
  65 /** Update the object-settable parts of a connectionpoints.
  66  * @param p A ConnectionPoint pointer (non-NULL).
  67  * @param x The x coordinate of the connectionpoint.
  68  * @param y The y coordinate of the connectionpoint.
  69  * @param dirs The directions that are open for connections on this point.
  70  */
  71 void
  72 connpoint_update(ConnectionPoint *p, real x, real y, gint dirs)
  73 {
  74   p->pos.x = x;
  75   p->pos.y = y;
  76   p->directions = dirs;
  77 }
  78
  79 /** Returns TRUE if the given connection point is non-null and autogapped.
  80  * @param cp A connectionpoint.
  81  * @returns TRUE if the given connection point is non-null and has the
  82  *  CP_FLAG_AUTOGAP flag set (i.e. lines connecting to it should try to end
  83  *  at the border of the object instead of at the connection point.
  84  */
  85 gboolean
  86 connpoint_is_autogap(ConnectionPoint *cp)
  87 {
  88   return cp != NULL && (cp->flags & CP_FLAG_AUTOGAP);
  89 }