Initial revision

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;
+}