| /* |
| ** 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 |
| #include <GL/glut.h> |
| |
| |
| GLenum doubleBuffer; |
| int dithering = 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; |
| default: |
| return; |
| } |
| |
| glutPostRedisplay(); |
| } |
| |
| static void Draw(void) |
| { |
| int i; |
| |
| glDisable(GL_BLEND); |
| |
| (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); |
| glBlendEquationEXT(GL_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"; |
| |
| 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); |
| if (!s) |
| exit(1); |
| if (strstr(s,extName) == 0) { |
| printf("Blend_logic_op extension is not present.\n"); |
| exit(1); |
| } |
| |
| Init(); |
| |
| glutReshapeFunc(Reshape); |
| glutKeyboardFunc(Key); |
| glutDisplayFunc(Draw); |
| glutMainLoop(); |
| return 0; |
| } |