/* ** blendxor.c - Demonstrates the use of the blend_logic_op ** extension to draw hilights. Using XOR to draw the same ** image twice restores the background to its original value. */ #include <stdio.h> #include <string.h> #ifndef _WIN32 #include <unistd.h> #endif #include <stdlib.h> #ifdef _WIN32 #include <windows.h> #endif #define GL_GLEXT_LEGACY #define GL_GLEXT_PROTOTYPES #include <GL/glut.h> #include <GL/glext.h> GLenum doubleBuffer; int dithering = 0; int use11ops = 0; int supportlogops = 0; GLint windW, windH; static void Init(void) { glDisable(GL_DITHER); glShadeModel(GL_FLAT); } static void Reshape(int width, int height) { windW = (GLint)width; windH = (GLint)height; glViewport(0, 0, (GLint)width, (GLint)height); glMatrixMode(GL_PROJECTION); glLoadIdentity(); gluOrtho2D(0, 400, 0, 400); glMatrixMode(GL_MODELVIEW); } static void Key(unsigned char key, int x, int y) { switch (key) { case 27: exit(1); case 'd': dithering = !dithering; break; case 'l': if (supportlogops == 3) use11ops = (!use11ops); if (use11ops) printf("Using GL 1.1 color logic ops.\n"); else printf("Using GL_EXT_blend_logic_op.\n"); break; default: return; } glutPostRedisplay(); } static void Draw(void) { int i; glDisable(GL_BLEND); if (supportlogops & 2) glDisable(GL_COLOR_LOGIC_OP); (dithering) ? glEnable(GL_DITHER) : glDisable(GL_DITHER); glClearColor(0.5, 0.6, 0.1, 1.0); glClear(GL_COLOR_BUFFER_BIT); /* Draw background prims */ glColor3f(0.1, 0.1, 1.0); glBegin(GL_TRIANGLES); glVertex2i(5, 5); glVertex2i(130, 50); glVertex2i(100, 300); glEnd(); glColor3f(0.5, 0.2, 0.9); glBegin(GL_TRIANGLES); glVertex2i(200, 100); glVertex2i(330, 50); glVertex2i(340, 400); glEnd(); glEnable(GL_BLEND); if (!use11ops) glBlendEquationEXT(GL_LOGIC_OP); else glEnable(GL_COLOR_LOGIC_OP); glLogicOp(GL_XOR); /* Draw a set of rectangles across the window */ glColor3f(0.9, 0.2, 0.8); for(i = 0; i < 400; i+=60) { glBegin(GL_POLYGON); glVertex2i(i, 100); glVertex2i(i+50, 100); glVertex2i(i+50, 200); glVertex2i(i, 200); glEnd(); } glFlush(); /* Added by Brian Paul */ #ifndef _WIN32 sleep(2); #endif /* Redraw the rectangles, which should erase them */ for(i = 0; i < 400; i+=60) { glBegin(GL_POLYGON); glVertex2i(i, 100); glVertex2i(i+50, 100); glVertex2i(i+50, 200); glVertex2i(i, 200); glEnd(); } glFlush(); if (doubleBuffer) { glutSwapBuffers(); } } static GLenum Args(int argc, char **argv) { GLint i; doubleBuffer = GL_FALSE; for (i = 1; i < argc; i++) { if (strcmp(argv[i], "-sb") == 0) { doubleBuffer = GL_FALSE; } else if (strcmp(argv[i], "-db") == 0) { doubleBuffer = GL_TRUE; } else { printf("%s (Bad option).\n", argv[i]); return GL_FALSE; } } return GL_TRUE; } int main(int argc, char **argv) { GLenum type; char *s; char *extName = "GL_EXT_blend_logic_op"; char *version; glutInit(&argc, argv); if (Args(argc, argv) == GL_FALSE) { exit(1); } glutInitWindowPosition(0, 0); glutInitWindowSize( 400, 400); type = GLUT_RGB; type |= (doubleBuffer) ? GLUT_DOUBLE : GLUT_SINGLE; glutInitDisplayMode(type); if (glutCreateWindow("Blend XOR") == GL_FALSE) { exit(1); } /* Make sure blend_logic_op extension is there. */ s = (char *) glGetString(GL_EXTENSIONS); version = (char*) glGetString(GL_VERSION); if (!s) exit(1); if (strstr(s,extName)) { supportlogops = 1; use11ops = 0; printf("blend_logic_op extension available.\n"); } if (strncmp(version,"1.1",3)>=0) { supportlogops += 2; use11ops = 1; printf("1.1 color logic ops available.\n"); } if (supportlogops == 0) { printf("Blend_logic_op extension and GL 1.1 not present.\n"); exit(1); } Init(); glutReshapeFunc(Reshape); glutKeyboardFunc(Key); glutDisplayFunc(Draw); glutMainLoop(); return 0; }