progs/trivial/clear-scissor.c

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