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Diffstat (limited to 'eel/eel-canvas-util.c')
| -rw-r--r-- | eel/eel-canvas-util.c | 426 |
1 files changed, 426 insertions, 0 deletions
diff --git a/eel/eel-canvas-util.c b/eel/eel-canvas-util.c new file mode 100644 index 00000000..ac90177f --- /dev/null +++ b/eel/eel-canvas-util.c @@ -0,0 +1,426 @@ +/* + * Copyright (C) 1997, 1998, 1999, 2000 Free Software Foundation + * All rights reserved. + * + * This file is part of the Mate Library. + * + * The Mate 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 Mate 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 Mate 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 <[email protected]> + */ + +#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; + if (poly == NULL) + return best; + + 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); +} + |