progs/samples/blendxor.c

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