/* * Copyright (C) 1997, 1998, 1999, 2000 Free Software Foundation * All rights reserved. * * This file is part of the Gnome Library. * * The Gnome Library is free software; you can redistribute it and/or * modify it under the terms of the GNU Library General Public License as * published by the Free Software Foundation; either version 2 of the * License, or (at your option) any later version. * * The Gnome Library is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * Library General Public License for more details. * * You should have received a copy of the GNU Library General Public * License along with the Gnome Library; see the file COPYING.LIB. If not, * write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, * Boston, MA 02111-1307, USA. */ /* @NOTATION@ */ /* Miscellaneous utility functions for the EelCanvas widget * * EelCanvas is basically a port of the Tk toolkit's most excellent canvas widget. Tk is * copyrighted by the Regents of the University of California, Sun Microsystems, and other parties. * * * Author: Federico Mena <federico@nuclecu.unam.mx> */ #include <config.h> #include <sys/types.h> #include <glib.h> #include <math.h> #include "eel-canvas.h" #include "eel-canvas-util.h" /* * Ok, so some systems require magic incantations for M_PI to be defined. * It's not important enough to worry about. */ #ifndef M_PI #define M_PI 3.141592653589793238462643383279502884197169399375105820974944592307816406286208998628034825342117 #endif /** * eel_canvas_points_new: * @num_points: The number of points to allocate space for in the array. * * Creates a structure that should be used to pass an array of points to * items. * * Return value: A newly-created array of points. It should be filled in * by the user. **/ EelCanvasPoints * eel_canvas_points_new (int num_points) { EelCanvasPoints *points; g_return_val_if_fail (num_points > 1, NULL); points = g_new (EelCanvasPoints, 1); points->num_points = num_points; points->coords = g_new (double, 2 * num_points); points->ref_count = 1; return points; } /** * eel_canvas_points_ref: * @points: A canvas points structure. * * Increases the reference count of the specified points structure. * * Return value: The canvas points structure itself. **/ EelCanvasPoints * eel_canvas_points_ref (EelCanvasPoints *points) { g_return_val_if_fail (points != NULL, NULL); points->ref_count += 1; return points; } /** * eel_canvas_points_free: * @points: A canvas points structure. * * Decreases the reference count of the specified points structure. If it * reaches zero, then the structure is freed. **/ void eel_canvas_points_free (EelCanvasPoints *points) { g_return_if_fail (points != NULL); points->ref_count -= 1; if (points->ref_count == 0) { g_free (points->coords); g_free (points); } } /** * eel_canvas_get_miter_points: * @x1: X coordinate of the first point * @y1: Y coordinate of the first point * @x2: X coordinate of the second (angle) point * @y2: Y coordinate of the second (angle) point * @x3: X coordinate of the third point * @y3: Y coordinate of the third point * @width: Width of the line * @mx1: The X coordinate of the first miter point is returned here. * @my1: The Y coordinate of the first miter point is returned here. * @mx2: The X coordinate of the second miter point is returned here. * @my2: The Y coordinate of the second miter point is returned here. * * Given three points forming an angle, computes the coordinates of the inside * and outside points of the mitered corner formed by a line of a given width at * that angle. * * Return value: FALSE if the angle is less than 11 degrees (this is the same * threshold as X uses. If this occurs, the return points are not modified. * Otherwise, returns TRUE. **/ int eel_canvas_get_miter_points (double x1, double y1, double x2, double y2, double x3, double y3, double width, double *mx1, double *my1, double *mx2, double *my2) { double theta1; /* angle of segment p2-p1 */ double theta2; /* angle of segment p2-p3 */ double theta; /* angle between line segments */ double theta3; /* angle that bisects theta1 and theta2 and points to p1 */ double dist; /* distance of miter points from p2 */ double dx, dy; /* x and y offsets corresponding to dist */ double ELEVEN_DEGREES = 11.0 * M_PI / 180.0; /* Degenerate cases. */ if ((x1 == x2 && y1 == y2) || (x2 == x3 && y2 == y3)) return FALSE; theta1 = atan2 (y1 - y2, x1 - x2); theta2 = atan2 (y3 - y2, x3 - x2); theta = theta1 - theta2; /* Normalize to (-pi; pi]. */ if (theta > M_PI) theta -= 2.0 * M_PI; else if (theta <= -M_PI) theta += 2.0 * M_PI; if (fabs (theta) < ELEVEN_DEGREES) return FALSE; dist = fabs (0.5 * width / sin (0.5 * theta)); theta3 = (theta1 + theta2) / 2.0; if (sin (theta3 - theta1) > 0.0) theta3 += M_PI; dx = dist * cos (theta3); dy = dist * sin (theta3); *mx1 = x2 + dx; *mx2 = x2 - dx; *my1 = y2 + dy; *my2 = y2 - dy; return TRUE; } /** * eel_canvas_get_butt_points: * @x1: X coordinate of first point in the line * @y1: Y cooordinate of first point in the line * @x2: X coordinate of second point (endpoint) of the line * @y2: Y coordinate of second point (endpoint) of the line * @width: Width of the line * @project: Whether the butt points should project out by width/2 distance * @bx1: X coordinate of first butt point is returned here * @by1: Y coordinate of first butt point is returned here * @bx2: X coordinate of second butt point is returned here * @by2: Y coordinate of second butt point is returned here * * Computes the butt points of a line segment. **/ void eel_canvas_get_butt_points (double x1, double y1, double x2, double y2, double width, int project, double *bx1, double *by1, double *bx2, double *by2) { double length; double dx, dy; width *= 0.5; dx = x2 - x1; dy = y2 - y1; length = sqrt (dx * dx + dy * dy); if (length < EEL_CANVAS_EPSILON) { *bx1 = *bx2 = x2; *by1 = *by2 = y2; } else { dx = -width * (y2 - y1) / length; dy = width * (x2 - x1) / length; *bx1 = x2 + dx; *bx2 = x2 - dx; *by1 = y2 + dy; *by2 = y2 - dy; if (project) { *bx1 += dy; *bx2 += dy; *by1 -= dx; *by2 -= dx; } } } /** * eel_canvas_polygon_to_point: * @poly: Vertices of the polygon. X coordinates are in the even indices, and Y * coordinates are in the odd indices * @num_points: Number of points in the polygon * @x: X coordinate of the point * @y: Y coordinate of the point * * Computes the distance between a point and a polygon. * * Return value: The distance from the point to the polygon, or zero if the * point is inside the polygon. **/ double eel_canvas_polygon_to_point (double *poly, int num_points, double x, double y) { double best; int intersections; int i; double *p; double dx, dy; /* Iterate through all the edges in the polygon, updating best and intersections. * * When computing intersections, include left X coordinate of line within its range, but not * Y coordinate. Otherwise if the point lies exactly below a vertex we'll count it as two * intersections. */ best = 1.0e36; intersections = 0; for (i = num_points, p = poly; i > 1; i--, p += 2) { double px, py, dist; /* Compute the point on the current edge closest to the point and update the * intersection count. This must be done separately for vertical edges, horizontal * edges, and others. */ if (p[2] == p[0]) { /* Vertical edge */ px = p[0]; if (p[1] >= p[3]) { py = MIN (p[1], y); py = MAX (py, p[3]); } else { py = MIN (p[3], y); py = MAX (py, p[1]); } } else if (p[3] == p[1]) { /* Horizontal edge */ py = p[1]; if (p[0] >= p[2]) { px = MIN (p[0], x); px = MAX (px, p[2]); if ((y < py) && (x < p[0]) && (x >= p[2])) intersections++; } else { px = MIN (p[2], x); px = MAX (px, p[0]); if ((y < py) && (x < p[2]) && (x >= p[0])) intersections++; } } else { double m1, b1, m2, b2; int lower; /* Diagonal edge. Convert the edge to a line equation (y = m1*x + b1), then * compute a line perpendicular to this edge but passing through the point, * (y = m2*x + b2). */ m1 = (p[3] - p[1]) / (p[2] - p[0]); b1 = p[1] - m1 * p[0]; m2 = -1.0 / m1; b2 = y - m2 * x; px = (b2 - b1) / (m1 - m2); py = m1 * px + b1; if (p[0] > p[2]) { if (px > p[0]) { px = p[0]; py = p[1]; } else if (px < p[2]) { px = p[2]; py = p[3]; } } else { if (px > p[2]) { px = p[2]; py = p[3]; } else if (px < p[0]) { px = p[0]; py = p[1]; } } lower = (m1 * x + b1) > y; if (lower && (x >= MIN (p[0], p[2])) && (x < MAX (p[0], p[2]))) intersections++; } /* Compute the distance to the closest point, and see if that is the best so far */ dx = x - px; dy = y - py; dist = sqrt (dx * dx + dy * dy); if (dist < best) best = dist; } /* We've processed all the points. If the number of intersections is odd, the point is * inside the polygon. */ if (intersections & 0x1) return 0.0; else return best; } /** * eel_canvas_item_reset_bounds: * @item: A canvas item * * Resets the bounding box of a canvas item to an empty rectangle. **/ void eel_canvas_item_reset_bounds (EelCanvasItem *item) { item->x1 = 0.0; item->y1 = 0.0; item->x2 = 0.0; item->y2 = 0.0; } /** * eel_canvas_update_bbox: * @canvas: the canvas needing update * @x1: Left coordinate of the new bounding box * @y1: Top coordinate of the new bounding box * @x2: Right coordinate of the new bounding box * @y2: Bottom coordinate of the new bounding box * * Sets the bbox to the new value, requesting full repaint. **/ void eel_canvas_update_bbox (EelCanvasItem *item, int x1, int y1, int x2, int y2) { eel_canvas_item_request_redraw (item); item->x1 = x1; item->y1 = y1; item->x2 = x2; item->y2 = y2; eel_canvas_item_request_redraw (item); }

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