RenderLogo.c revision 3fe82118 
1/*
2
3Copyright 1988, 1998  The Open Group
4
5Permission to use, copy, modify, distribute, and sell this software and its
6documentation for any purpose is hereby granted without fee, provided that
7the above copyright notice appear in all copies and that both that
8copyright notice and this permission notice appear in supporting
9documentation.
10
11The above copyright notice and this permission notice shall be included in
12all copies or substantial portions of the Software.
13
14THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
15IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
16FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
17OPEN GROUP BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
18AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
19CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
20
21Except as contained in this notice, the name of The Open Group shall not be
22used in advertising or otherwise to promote the sale, use or other dealings
23in this Software without prior written authorization from The Open Group.
24
25*/
26
27#ifdef HAVE_CONFIG_H
28#include <config.h>
29#endif
30
31#ifdef XRENDER
32#include <stdio.h>
33
34#include <X11/Xlib.h>
35#include <X11/extensions/Xrender.h>
36
37#include "RenderLogo.h"
38
39typedef struct _XLineDouble {
40    XPointDouble  p1, p2;
41} XLineDouble;
42
43static void
44intersect(XLineDouble *l1, XLineDouble *l2, XPointDouble *intersection);
45
46/*
47 *  Draw the "official" X Window System Logo, designed by Danny Chong
48 *
49 *  Written by Ollie Jones, Apollo Computer
50 *
51 *  Does some fancy stuff to make the logo look acceptable even
52 *  if it is tiny.  Also makes the various linear elements of
53 *  the logo line up as well as possible considering rasterization.
54 *
55 *  Munged to draw anti-aliased logo using Render extension.
56 *  Carl Worth, 2002-05-16
57 */
58void
59RenderLogo(Display *dpy, int op, Picture src, Picture dst, XRenderPictFormat *maskFormat,
60	   int x, int y, unsigned int width, unsigned int height)
61{
62    unsigned int size;
63    double thin, thick, gap, d31;
64    XPointDouble poly[6];
65    XLineDouble thick_left, thick_right, thin_left, thin_right, gap_left, gap_right;
66
67    /* for now, do a centered even-sized square, at least for now */
68    size = width;
69    if (height < width)
70	 size = height;
71    size &= ~1;
72    x += (width - size) >> 1;
73    y += (height - size) >> 1;
74
75    thin = (size / 11.0);
76    thick = (size / 4.0);
77    gap = thin / 4.0;
78    d31 = thin + thin + gap;
79
80    thick_left.p1.x = x;		thick_left.p1.y = y;
81    thick_left.p2.x = x + size - thick;	thick_left.p2.y = y + size;
82
83    thick_right.p1.x = x + thick;	thick_right.p1.y = y;
84    thick_right.p2.x = x + size;	thick_right.p2.y = y + size;
85
86    thin_left.p1.x = x + size-d31;	thin_left.p1.y = y;
87    thin_left.p2.x = x + 0;		thin_left.p2.y = y + size;
88
89    thin_right.p1.x = x + size;		thin_right.p1.y = y;
90    thin_right.p2.x = x + d31;		thin_right.p2.y = y + size;
91
92    gap_left.p1.x = x + size-( thin+gap);	gap_left.p1.y = y;
93    gap_left.p2.x = x + thin;			gap_left.p2.y = y + size;
94
95    gap_right.p1.x = x + size- thin;	gap_right.p1.y = y;
96    gap_right.p2.x = x + thin + gap;	gap_right.p2.y = y + size;
97
98    poly[0] = thick_left.p1;
99    poly[1] = thick_right.p1;
100    intersect(&thick_right, &gap_left, &poly[2]);
101    poly[3] = gap_left.p2;
102    poly[4] = thin_left.p2;
103    intersect(&thick_left, &thin_left, &poly[5]);
104
105    XRenderCompositeDoublePoly(dpy, op,
106			       src, dst, maskFormat,
107			       0, 0, 0, 0,
108			       poly, 6, 0);
109
110    poly[0] = thin_right.p1;
111    poly[1] = gap_right.p1;
112    intersect(&thick_left, &gap_right, &poly[2]);
113    poly[3] = thick_left.p2;
114    poly[4] = thick_right.p2;
115    intersect(&thick_right, &thin_right, &poly[5]);
116
117    XRenderCompositeDoublePoly(dpy, op,
118			       src, dst, maskFormat,
119			       0, 0, 0, 0,
120			       poly, 6, 0);
121}
122
123static double
124compute_inverse_slope (XLineDouble *l)
125{
126    return ((l->p2.x - l->p1.x) /
127	    (l->p2.y - l->p1.y));
128}
129
130static double
131compute_x_intercept(XLineDouble *l, double inverse_slope)
132{
133    return (l->p1.x) - inverse_slope * l->p1.y;
134}
135
136static void
137intersect(XLineDouble *l1, XLineDouble *l2, XPointDouble *intersection)
138{
139    double check;
140    /*
141     * x = m1y + b1
142     * x = m2y + b2
143     * m1y + b1 = m2y + b2
144     * y * (m1 - m2) = b2 - b1
145     * y = (b2 - b1) / (m1 - m2)
146     */
147    double  m1 = compute_inverse_slope (l1);
148    double  b1 = compute_x_intercept (l1, m1);
149    double  m2 = compute_inverse_slope (l2);
150    double  b2 = compute_x_intercept (l2, m2);
151
152    intersection->y = (b2 - b1) / (m1 - m2);
153    intersection->x = m1 * intersection->y + b1;
154
155    check = m2 * intersection->y + b2;
156    if (check >= intersection->x)
157	check -= intersection->x;
158    else
159	check = intersection->x - check;
160    if (check > (1/(double)(1<<16))) {
161	fprintf(stderr, "intersect: intersection is off by %f\n", check);
162    }
163}
164#endif /* XRENDER */
165