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2008-01-14 Martin Nordholts <martinn@svn.gnome.org> * app/tools/tools-utils.[ch] (gimp_tool_motion_constrain): Generalized to allow a variable number of lines for snapping, and rewritten to make snapping happen more intuitively; snap the shortest distance rather than only horizontally or vertically. (gimp_tool_utils_point_to_line_distance): New helper function. * app/tools/gimpblendtool.c * app/tools/gimpmeasuretool.c * app/tools/gimppainttool.c: Adjust to the new function signature. svn path=/trunk/; revision=24609
120 lines
4.1 KiB
C
120 lines
4.1 KiB
C
/* GIMP - The GNU Image Manipulation Program
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* Copyright (C) 1995 Spencer Kimball and Peter Mattis
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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*/
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#include "config.h"
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#include <glib-object.h>
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#include "libgimpmath/gimpmath.h"
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#include "tools-utils.h"
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static gdouble gimp_tool_utils_point_to_line_distance (const GimpVector2 *point,
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const GimpVector2 *point_on_line,
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const GimpVector2 *normalized_line_direction,
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GimpVector2 *closest_line_point);
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/**
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* gimp_tool_utils_point_to_line_distance:
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* @point: The point to calculate the distance for.
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* @point_on_line: A point on the line.
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* @line_direction: Normalized line direction vector.
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* @closest_line_point: Gets set to the point on the line that is
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* closest to @point.
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*
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* Returns: The shortest distance from @point to the line defined by
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* @point_on_line and @normalized_line_direction.
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**/
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static gdouble
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gimp_tool_utils_point_to_line_distance (const GimpVector2 *point,
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const GimpVector2 *point_on_line,
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const GimpVector2 *line_direction,
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GimpVector2 *closest_line_point)
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{
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GimpVector2 distance_vector;
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GimpVector2 tmp_a;
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GimpVector2 tmp_b;
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gdouble d;
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gimp_vector2_sub (&tmp_a, point, point_on_line);
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d = gimp_vector2_inner_product (&tmp_a, line_direction);
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tmp_b = gimp_vector2_mul_val (*line_direction, d);
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*closest_line_point = gimp_vector2_add_val (*point_on_line,
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tmp_b);
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gimp_vector2_sub (&distance_vector, closest_line_point, point);
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return gimp_vector2_length (&distance_vector);
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}
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/**
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* gimp_tool_motion_constrain:
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* @start_x:
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* @start_y:
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* @end_x:
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* @end_y:
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* @n_snap_lines: Number evenly disributed lines to snap to.
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*
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* Projects a line onto the specified subset of evenly radially
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* distributed lines. @n_lines of 2 makes the line snap horizontally
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* or vertically. @n_lines of 4 snaps on 45 degree steps. @n_lines of
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* 12 on 15 degree steps. etc.
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**/
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void
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gimp_tool_motion_constrain (gdouble start_x,
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gdouble start_y,
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gdouble *end_x,
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gdouble *end_y,
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gint n_snap_lines)
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{
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GimpVector2 line_point = { start_x, start_y };
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GimpVector2 point = { *end_x, *end_y };
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GimpVector2 constrained_point;
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GimpVector2 line_dir;
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gdouble shortest_dist_moved = G_MAXDOUBLE;
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gdouble dist_moved;
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gdouble angle;
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gint i;
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for (i = 0; i < n_snap_lines; i++)
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{
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angle = i * G_PI / n_snap_lines;
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gimp_vector2_set (&line_dir,
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cos (angle),
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sin (angle));
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dist_moved = gimp_tool_utils_point_to_line_distance (&point,
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&line_point,
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&line_dir,
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&constrained_point);
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if (dist_moved < shortest_dist_moved)
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{
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shortest_dist_moved = dist_moved;
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*end_x = constrained_point.x;
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*end_y = constrained_point.y;
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}
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}
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}
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