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 #include <GL/glew.h>
  14 #include <GL/glut.h>
  15
  16
  17 GLenum doubleBuffer;
  18 int dithering = 0;
  19 int use11ops = 0;
  20 int supportlogops = 0;
  21 GLint windW, windH;
  22
  23 static void Init(void)
  24 {
  25     glDisable(GL_DITHER);
  26     glShadeModel(GL_FLAT);
  27 }
  28
  29 static 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
  43 static 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
  66 static 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
 132 static 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
 151 int 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 }