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 #define GL_GLEXT_PROTOTYPES
  18 #include <GL/glut.h>
  19 #include <GL/glext.h>
  20
  21
  22 GLenum doubleBuffer;
  23 int dithering = 0;
  24 int use11ops = 0;
  25 int supportlogops = 0;
  26 GLint windW, windH;
  27
  28 static void Init(void)
  29 {
  30     glDisable(GL_DITHER);
  31     glShadeModel(GL_FLAT);
  32 }
  33
  34 static void Reshape(int width, int height)
  35 {
  36
  37     windW = (GLint)width;
  38     windH = (GLint)height;
  39
  40     glViewport(0, 0, (GLint)width, (GLint)height);
  41
  42     glMatrixMode(GL_PROJECTION);
  43     glLoadIdentity();
  44     gluOrtho2D(0, 400, 0, 400);
  45     glMatrixMode(GL_MODELVIEW);
  46 }
  47
  48 static void Key(unsigned char key, int x, int y)
  49 {
  50
  51     switch (key) {
  52       case 27:
  53         exit(1);
  54       case 'd':
  55         dithering = !dithering;
  56         break;
  57       case 'l':
  58         if (supportlogops == 3)
  59            use11ops = (!use11ops);
  60         if (use11ops)
  61            printf("Using GL 1.1 color logic ops.\n");
  62         else printf("Using GL_EXT_blend_logic_op.\n");
  63         break;
  64       default:
  65         return;
  66     }
  67
  68     glutPostRedisplay();
  69 }
  70
  71 static void Draw(void)
  72 {
  73     int i;
  74
  75     glDisable(GL_BLEND);
  76     if (supportlogops & 2)
  77        glDisable(GL_COLOR_LOGIC_OP);
  78
  79     (dithering) ? glEnable(GL_DITHER) : glDisable(GL_DITHER);
  80
  81     glClearColor(0.5, 0.6, 0.1, 1.0);
  82     glClear(GL_COLOR_BUFFER_BIT);
  83
  84     /* Draw background prims */
  85     glColor3f(0.1, 0.1, 1.0);
  86     glBegin(GL_TRIANGLES);
  87         glVertex2i(5, 5);
  88         glVertex2i(130, 50);
  89         glVertex2i(100,  300);
  90     glEnd();
  91     glColor3f(0.5, 0.2, 0.9);
  92     glBegin(GL_TRIANGLES);
  93         glVertex2i(200, 100);
  94         glVertex2i(330, 50);
  95         glVertex2i(340,  400);
  96     glEnd();
  97
  98     glEnable(GL_BLEND);
  99     if (!use11ops)
 100        glBlendEquationEXT(GL_LOGIC_OP);
 101     else
 102        glEnable(GL_COLOR_LOGIC_OP);
 103     glLogicOp(GL_XOR);
 104
 105     /* Draw a set of rectangles across the window */
 106     glColor3f(0.9, 0.2, 0.8);
 107     for(i = 0; i < 400; i+=60) {
 108         glBegin(GL_POLYGON);
 109             glVertex2i(i, 100);
 110             glVertex2i(i+50, 100);
 111             glVertex2i(i+50, 200);
 112             glVertex2i(i, 200);
 113         glEnd();
 114     }
 115     glFlush();   /* Added by Brian Paul */
 116 #ifndef _WIN32
 117     sleep(2);
 118 #endif
 119
 120     /* Redraw  the rectangles, which should erase them */
 121     for(i = 0; i < 400; i+=60) {
 122         glBegin(GL_POLYGON);
 123             glVertex2i(i, 100);
 124             glVertex2i(i+50, 100);
 125             glVertex2i(i+50, 200);
 126             glVertex2i(i, 200);
 127         glEnd();
 128     }
 129     glFlush();
 130
 131
 132     if (doubleBuffer) {
 133         glutSwapBuffers();
 134     }
 135 }
 136
 137 static GLenum Args(int argc, char **argv)
 138 {
 139     GLint i;
 140
 141     doubleBuffer = GL_FALSE;
 142
 143     for (i = 1; i < argc; i++) {
 144         if (strcmp(argv[i], "-sb") == 0) {
 145             doubleBuffer = GL_FALSE;
 146         } else if (strcmp(argv[i], "-db") == 0) {
 147             doubleBuffer = GL_TRUE;
 148         } else {
 149             printf("%s (Bad option).\n", argv[i]);
 150             return GL_FALSE;
 151         }
 152     }
 153     return GL_TRUE;
 154 }
 155
 156 int main(int argc, char **argv)
 157 {
 158     GLenum type;
 159     char *s;
 160     char *extName = "GL_EXT_blend_logic_op";
 161     char *version;
 162
 163     glutInit(&argc, argv);
 164
 165     if (Args(argc, argv) == GL_FALSE) {
 166         exit(1);
 167     }
 168
 169     glutInitWindowPosition(0, 0); glutInitWindowSize( 400, 400);
 170
 171     type = GLUT_RGB;
 172     type |= (doubleBuffer) ? GLUT_DOUBLE : GLUT_SINGLE;
 173     glutInitDisplayMode(type);
 174
 175     if (glutCreateWindow("Blend XOR") == GL_FALSE) {
 176         exit(1);
 177     }
 178
 179     /* Make sure blend_logic_op extension is there. */
 180     s = (char *) glGetString(GL_EXTENSIONS);
 181     version = (char*) glGetString(GL_VERSION);
 182     if (!s)
 183         exit(1);
 184     if (strstr(s,extName)) {
 185         supportlogops = 1;
 186         use11ops = 0;
 187         printf("blend_logic_op extension available.\n");
 188     }
 189     if (strncmp(version,"1.1",3)>=0) {
 190         supportlogops += 2;
 191         use11ops = 1;
 192         printf("1.1 color logic ops available.\n");
 193     }
 194     if (supportlogops == 0) {
 195         printf("Blend_logic_op extension and GL 1.1 not present.\n");
 196         exit(1);
 197     }
 198
 199     Init();
 200
 201     glutReshapeFunc(Reshape);
 202     glutKeyboardFunc(Key);
 203     glutDisplayFunc(Draw);
 204     glutMainLoop();
 205         return 0;
 206 }