Initial revision
diff --git a/progs/samples/blendxor.c b/progs/samples/blendxor.c
new file mode 100644
index 0000000..a46920d
--- /dev/null
+++ b/progs/samples/blendxor.c
@@ -0,0 +1,174 @@
+/*
+** 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>
+#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;
+}