1/*
2 * glClear + glScissor + Undefined content of framebuffer
3 */
4
5#include <stdio.h>
6#include <string.h>
7#include <stdlib.h>
8#include "glut_wrap.h"
9
10
11GLenum doubleBuffer;
12GLint Width = 200, Height = 150;
13
14static void Init(void)
15{
16   fprintf(stderr, "GL_RENDERER   = %s\n", (char *) glGetString(GL_RENDERER));
17   fprintf(stderr, "GL_VERSION    = %s\n", (char *) glGetString(GL_VERSION));
18   fprintf(stderr, "GL_VENDOR     = %s\n", (char *) glGetString(GL_VENDOR));
19   fprintf(stderr, "Top right corner should be red\n");
20   fflush(stderr);
21}
22
23static void Reshape(int width, int height)
24{
25   Width = width;
26   Height = height;
27
28   glViewport(0, 0, (GLint)width, (GLint)height);
29
30   glMatrixMode(GL_PROJECTION);
31   glLoadIdentity();
32   glOrtho(-1.0, 1.0, -1.0, 1.0, -0.5, 1000.0);
33   glMatrixMode(GL_MODELVIEW);
34}
35
36static void Key(unsigned char key, int x, int y)
37{
38    switch (key) {
39      case 27:
40	exit(1);
41      default:
42	glutPostRedisplay();
43	return;
44    }
45
46}
47
48static void Draw(void)
49{
50   glColor4f(1.0, 0.0, 0.0, 1.0);
51   glBegin(GL_QUADS);
52   glVertex2d(0.0, 0.0);
53   glVertex2d(0.0, 1.0);
54   glVertex2d(1.0, 1.0);
55   glVertex2d(1.0, 0.0);
56   glEnd();
57
58   glBegin(GL_QUADS);
59   glVertex2d(0.0,  0.0);
60   glVertex2d(0.0, -1.0);
61   glVertex2d(1.0, -1.0);
62   glVertex2d(1.0,  0.0);
63   glEnd();
64
65   glEnable(GL_SCISSOR_TEST);
66   glClearColor(1, 1, 0, 0);
67   glScissor(Width / 2, 0, Width - Width / 2, Height / 2);
68   glClear(GL_COLOR_BUFFER_BIT);
69
70   glClearColor(0, 0, 1, 0);
71   glScissor(0, Height / 2, Width / 2, Height - Height / 2);
72   glClear(GL_COLOR_BUFFER_BIT);
73   glDisable(GL_SCISSOR_TEST);
74
75   glColor4f(0.0, 1.0, 0.0, 1.0);
76   glBegin(GL_QUADS);
77   glVertex2d( 0.0,  0.0);
78   glVertex2d( 0.0, -1.0);
79   glVertex2d(-1.0, -1.0);
80   glVertex2d(-1.0,  0.0);
81   glEnd();
82
83   glFlush();
84
85   if (doubleBuffer) {
86      glutSwapBuffers();
87   }
88}
89
90static GLenum Args(int argc, char **argv)
91{
92    GLint i;
93
94    doubleBuffer = GL_TRUE;
95
96    for (i = 1; i < argc; i++) {
97        if (strcmp(argv[i], "-sb") == 0) {
98	    doubleBuffer = GL_FALSE;
99	} else if (strcmp(argv[i], "-db") == 0) {
100	    doubleBuffer = GL_TRUE;
101	} else {
102	    fprintf(stderr, "%s (Bad option).\n", argv[i]);
103	    return GL_FALSE;
104	}
105    }
106    return GL_TRUE;
107}
108
109int main(int argc, char **argv)
110{
111    GLenum type;
112
113    glutInit(&argc, argv);
114
115    if (Args(argc, argv) == GL_FALSE) {
116	exit(1);
117    }
118
119    glutInitWindowPosition(0, 0); glutInitWindowSize( Width, Height );
120
121
122    type = GLUT_RGB | GLUT_ALPHA;
123    type |= (doubleBuffer) ? GLUT_DOUBLE : GLUT_SINGLE;
124    glutInitDisplayMode(type);
125
126    if (glutCreateWindow(argv[0]) == GL_FALSE) {
127	exit(1);
128    }
129
130    Init();
131	Reshape(Width, Height);
132
133    glutReshapeFunc(Reshape);
134    glutKeyboardFunc(Key);
135    glutDisplayFunc(Draw);
136    glutMainLoop();
137    return 0;
138}
139