1/*
2** blendxor.c - Demonstrates the use of the blend_logic_op
3**    extension to draw hilights.  Using XOR to draw the same
4**    image twice restores the background to its original value.
5*/
6
7#include <stdio.h>
8#include <string.h>
9#ifndef _WIN32
10#include <unistd.h>
11#endif
12#include <stdlib.h>
13#include <GL/glew.h>
14#include "glut_wrap.h"
15
16
17GLenum doubleBuffer;
18int dithering = 0;
19int use11ops = 0;
20int supportlogops = 0;
21GLint windW, windH;
22
23static void Init(void)
24{
25    glDisable(GL_DITHER);
26    glShadeModel(GL_FLAT);
27}
28
29static void Reshape(int width, int height)
30{
31
32    windW = (GLint)width;
33    windH = (GLint)height;
34
35    glViewport(0, 0, (GLint)width, (GLint)height);
36
37    glMatrixMode(GL_PROJECTION);
38    glLoadIdentity();
39    gluOrtho2D(0, 400, 0, 400);
40    glMatrixMode(GL_MODELVIEW);
41}
42
43static void Key(unsigned char key, int x, int y)
44{
45
46    switch (key) {
47      case 27:
48	exit(1);
49      case 'd':
50	dithering = !dithering;
51	break;
52      case 'l':
53        if (supportlogops == 3)
54           use11ops = (!use11ops);
55        if (use11ops)
56           printf("Using GL 1.1 color logic ops.\n");
57        else printf("Using GL_EXT_blend_logic_op.\n");
58        break;
59      default:
60	return;
61    }
62
63    glutPostRedisplay();
64}
65
66static void Draw(void)
67{
68    int i;
69
70    glDisable(GL_BLEND);
71    if (supportlogops & 2)
72       glDisable(GL_COLOR_LOGIC_OP);
73
74    (dithering) ? glEnable(GL_DITHER) : glDisable(GL_DITHER);
75
76    glClearColor(0.5, 0.6, 0.1, 1.0);
77    glClear(GL_COLOR_BUFFER_BIT);
78
79    /* Draw background prims */
80    glColor3f(0.1, 0.1, 1.0);
81    glBegin(GL_TRIANGLES);
82        glVertex2i(5, 5);
83        glVertex2i(130, 50);
84        glVertex2i(100,  300);
85    glEnd();
86    glColor3f(0.5, 0.2, 0.9);
87    glBegin(GL_TRIANGLES);
88        glVertex2i(200, 100);
89        glVertex2i(330, 50);
90        glVertex2i(340,  400);
91    glEnd();
92
93    glEnable(GL_BLEND);
94    if (!use11ops)
95       glBlendEquationEXT(GL_LOGIC_OP);
96    else
97       glEnable(GL_COLOR_LOGIC_OP);
98    glLogicOp(GL_XOR);
99
100    /* Draw a set of rectangles across the window */
101    glColor3f(0.9, 0.2, 0.8);
102    for(i = 0; i < 400; i+=60) {
103        glBegin(GL_POLYGON);
104            glVertex2i(i, 100);
105            glVertex2i(i+50, 100);
106            glVertex2i(i+50, 200);
107            glVertex2i(i, 200);
108        glEnd();
109    }
110    glFlush();   /* Added by Brian Paul */
111#ifndef _WIN32
112    sleep(2);
113#endif
114
115    /* Redraw  the rectangles, which should erase them */
116    for(i = 0; i < 400; i+=60) {
117        glBegin(GL_POLYGON);
118            glVertex2i(i, 100);
119            glVertex2i(i+50, 100);
120            glVertex2i(i+50, 200);
121            glVertex2i(i, 200);
122        glEnd();
123    }
124    glFlush();
125
126
127    if (doubleBuffer) {
128	glutSwapBuffers();
129    }
130}
131
132static GLenum Args(int argc, char **argv)
133{
134    GLint i;
135
136    doubleBuffer = GL_FALSE;
137
138    for (i = 1; i < argc; i++) {
139	if (strcmp(argv[i], "-sb") == 0) {
140	    doubleBuffer = GL_FALSE;
141	} else if (strcmp(argv[i], "-db") == 0) {
142	    doubleBuffer = GL_TRUE;
143	} else {
144	    printf("%s (Bad option).\n", argv[i]);
145	    return GL_FALSE;
146	}
147    }
148    return GL_TRUE;
149}
150
151int main(int argc, char **argv)
152{
153    GLenum type;
154    char *s;
155    char *extName = "GL_EXT_blend_logic_op";
156    char *version;
157
158    glutInit(&argc, argv);
159
160    if (Args(argc, argv) == GL_FALSE) {
161	exit(1);
162    }
163
164    glutInitWindowPosition(0, 0); glutInitWindowSize( 400, 400);
165
166    type = GLUT_RGB;
167    type |= (doubleBuffer) ? GLUT_DOUBLE : GLUT_SINGLE;
168    glutInitDisplayMode(type);
169
170    if (glutCreateWindow("Blend XOR") == GL_FALSE) {
171	exit(1);
172    }
173
174    glewInit();
175
176    /* Make sure blend_logic_op extension is there. */
177    s = (char *) glGetString(GL_EXTENSIONS);
178    version = (char*) glGetString(GL_VERSION);
179    if (!s)
180	exit(1);
181    if (strstr(s,extName)) {
182	supportlogops = 1;
183        use11ops = 0;
184        printf("blend_logic_op extension available.\n");
185    }
186    if (strncmp(version,"1.1",3)>=0) {
187    	supportlogops += 2;
188        use11ops = 1;
189	printf("1.1 color logic ops available.\n");
190    }
191    if (supportlogops == 0) {
192    	printf("Blend_logic_op extension and GL 1.1 not present.\n");
193	exit(1);
194    }
195
196    Init();
197
198    glutReshapeFunc(Reshape);
199    glutKeyboardFunc(Key);
200    glutDisplayFunc(Draw);
201    glutMainLoop();
202	return 0;
203}
204