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    fflush(stderr);
  20 }
  21
  22 static void Reshape(int width, int height)
  23 {
  24    Width = width;
  25    Height = height;
  26
  27    glViewport(0, 0, (GLint)width, (GLint)height);
  28
  29    glMatrixMode(GL_PROJECTION);
  30    glLoadIdentity();
  31    glOrtho(-1.0, 1.0, -1.0, 1.0, -0.5, 1000.0);
  32    glMatrixMode(GL_MODELVIEW);
  33 }
  34
  35 static void Key(unsigned char key, int x, int y)
  36 {
  37     switch (key) {
  38       case 27:
  39         exit(1);
  40       default:
  41         break;
  42     }
  43     glutPostRedisplay();
  44 }
  45
  46 static void Draw(void)
  47 {
  48    glEnable(GL_SCISSOR_TEST);
  49
  50    glClearColor(1, 0, 0, 0);
  51    glScissor(0, 0, Width / 2, Height / 2);
  52    glClear(GL_COLOR_BUFFER_BIT);
  53
  54    glClearColor(0, 1, 0, 0);
  55    glScissor(Width / 2, 0, Width - Width / 2, Height / 2);
  56    glClear(GL_COLOR_BUFFER_BIT);
  57
  58    glClearColor(0, 0, 1, 0);
  59    glScissor(0, Height / 2, Width / 2, Height - Height / 2);
  60    glClear(GL_COLOR_BUFFER_BIT);
  61
  62    glClearColor(1, 1, 1, 0);
  63    glScissor(Width / 2, Height / 2, Width - Width / 2, Height - Height / 2);
  64    glClear(GL_COLOR_BUFFER_BIT);
  65
  66    glFlush();
  67
  68    if (doubleBuffer) {
  69       glutSwapBuffers();
  70    }
  71 }
  72
  73 static GLenum Args(int argc, char **argv)
  74 {
  75     GLint i;
  76
  77     doubleBuffer = GL_FALSE;
  78
  79     for (i = 1; i < argc; i++) {
  80         if (strcmp(argv[i], "-sb") == 0) {
  81             doubleBuffer = GL_FALSE;
  82         } else if (strcmp(argv[i], "-db") == 0) {
  83             doubleBuffer = GL_TRUE;
  84         } else {
  85             fprintf(stderr, "%s (Bad option).\n", argv[i]);
  86             return GL_FALSE;
  87         }
  88     }
  89     return GL_TRUE;
  90 }
  91
  92 int main(int argc, char **argv)
  93 {
  94     GLenum type;
  95
  96     glutInit(&argc, argv);
  97
  98     if (Args(argc, argv) == GL_FALSE) {
  99         exit(1);
 100     }
 101
 102     glutInitWindowPosition(0, 0); glutInitWindowSize( Width, Height );
 103
 104     type = GLUT_RGB | GLUT_ALPHA;
 105     type |= (doubleBuffer) ? GLUT_DOUBLE : GLUT_SINGLE;
 106     glutInitDisplayMode(type);
 107
 108     if (glutCreateWindow(argv[0]) == GL_FALSE) {
 109         exit(1);
 110     }
 111
 112     Init();
 113
 114     glutReshapeFunc(Reshape);
 115     glutKeyboardFunc(Key);
 116     glutDisplayFunc(Draw);
 117     glutMainLoop();
 118     return 0;
 119 }