stroke.c

OpenGL学习资料

/*
 * Copyright (c) 1993-1999, Silicon Graphics, Inc.
 * ALL RIGHTS RESERVED 
 * Permission to use, copy, modify, and distribute this software for 
 * any purpose and without fee is hereby granted, provided that the above
 * copyright notice appear in all copies and that both the copyright notice
 * and this permission notice appear in supporting documentation, and that 
 * the name of Silicon Graphics, Inc. not be used in advertising
 * or publicity pertaining to distribution of the software without specific,
 * written prior permission. 
 *
 * THE MATERIAL EMBODIED ON THIS SOFTWARE IS PROVIDED TO YOU "AS-IS"
 * AND WITHOUT WARRANTY OF ANY KIND, EXPRESS, IMPLIED OR OTHERWISE,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTY OF MERCHANTABILITY OR
 * FITNESS FOR A PARTICULAR PURPOSE.  IN NO EVENT SHALL SILICON
 * GRAPHICS, INC.  BE LIABLE TO YOU OR ANYONE ELSE FOR ANY DIRECT,
 * SPECIAL, INCIDENTAL, INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY
 * KIND, OR ANY DAMAGES WHATSOEVER, INCLUDING WITHOUT LIMITATION,
 * LOSS OF PROFIT, LOSS OF USE, SAVINGS OR REVENUE, OR THE CLAIMS OF
 * THIRD PARTIES, WHETHER OR NOT SILICON GRAPHICS, INC.  HAS BEEN
 * ADVISED OF THE POSSIBILITY OF SUCH LOSS, HOWEVER CAUSED AND ON
 * ANY THEORY OF LIABILITY, ARISING OUT OF OR IN CONNECTION WITH THE
 * POSSESSION, USE OR PERFORMANCE OF THIS SOFTWARE.
 * 
 * US Government Users Restricted Rights 
 * Use, duplication, or disclosure by the Government is subject to
 * restrictions set forth in FAR 52.227.19(c)(2) or subparagraph
 * (c)(1)(ii) of the Rights in Technical Data and Computer Software
 * clause at DFARS 252.227-7013 and/or in similar or successor
 * clauses in the FAR or the DOD or NASA FAR Supplement.
 * Unpublished-- rights reserved under the copyright laws of the
 * United States.  Contractor/manufacturer is Silicon Graphics,
 * Inc., 2011 N.  Shoreline Blvd., Mountain View, CA 94039-7311.
 *
 * OpenGL(R) is a registered trademark of Silicon Graphics, Inc.
 */

/*
 *  stroke.c 
 *  This program demonstrates some characters of a 
 *  stroke (vector) font.  The characters are represented
 *  by display lists, which are given numbers which 
 *  correspond to the ASCII values of the characters.
 *  Use of glCallLists() is demonstrated.
 */
#include <GL/glut.h>
#include <stdlib.h>
#include <string.h>

#define PT 1
#define STROKE 2
#define END 3

typedef struct charpoint {
   GLfloat   x, y;
   int    type;
} CP;

CP Adata[] = {
   { 0, 0, PT}, {0, 9, PT}, {1, 10, PT}, {4, 10, PT}, 
   {5, 9, PT}, {5, 0, STROKE}, {0, 5, PT}, {5, 5, END}
};

CP Edata[] = {
   {5, 0, PT}, {0, 0, PT}, {0, 10, PT}, {5, 10, STROKE},
   {0, 5, PT}, {4, 5, END}
};

CP Pdata[] = {
   {0, 0, PT}, {0, 10, PT},  {4, 10, PT}, {5, 9, PT}, {5, 6, PT}, 
   {4, 5, PT}, {0, 5, END}
};

CP Rdata[] = {
   {0, 0, PT}, {0, 10, PT},  {4, 10, PT}, {5, 9, PT}, {5, 6, PT}, 
   {4, 5, PT}, {0, 5, STROKE}, {3, 5, PT}, {5, 0, END}
};

CP Sdata[] = {
   {0, 1, PT}, {1, 0, PT}, {4, 0, PT}, {5, 1, PT}, {5, 4, PT}, 
   {4, 5, PT}, {1, 5, PT}, {0, 6, PT}, {0, 9, PT}, {1, 10, PT}, 
   {4, 10, PT}, {5, 9, END}
};

/*  drawLetter() interprets the instructions from the array
 *  for that letter and renders the letter with line segments.
 */
static void drawLetter(CP *l)
{
   glBegin(GL_LINE_STRIP);
   while (1) {
      switch (l->type) {
         case PT:
            glVertex2fv(&l->x);
            break;
         case STROKE:
            glVertex2fv(&l->x);
            glEnd();
            glBegin(GL_LINE_STRIP);
            break;
         case END:
            glVertex2fv(&l->x);
            glEnd();
            glTranslatef(8.0, 0.0, 0.0);
            return;
      }
      l++;
   }
}

/*  Create a display list for each of 6 characters	*/
static void init (void)
{
   GLuint base;

   glShadeModel (GL_FLAT);

   base = glGenLists (128);
   glListBase(base);
   glNewList(base+'A', GL_COMPILE); drawLetter(Adata); glEndList();
   glNewList(base+'E', GL_COMPILE); drawLetter(Edata); glEndList();
   glNewList(base+'P', GL_COMPILE); drawLetter(Pdata); glEndList();
   glNewList(base+'R', GL_COMPILE); drawLetter(Rdata); glEndList();
   glNewList(base+'S', GL_COMPILE); drawLetter(Sdata); glEndList();
   glNewList(base+' ', GL_COMPILE); glTranslatef(8.0, 0.0, 0.0); glEndList();
}

char *test1 = "A SPARE SERAPE APPEARS AS";
char *test2 = "APES PREPARE RARE PEPPERS";

static void printStrokedString(char *s)
{
   GLsizei len = strlen(s);
   glCallLists(len, GL_BYTE, (GLbyte *)s);
}

void display(void)
{
   glClear(GL_COLOR_BUFFER_BIT);
   glColor3f(1.0, 1.0, 1.0);
   glPushMatrix();
   glScalef(2.0, 2.0, 2.0);
   glTranslatef(10.0, 30.0, 0.0);
   printStrokedString(test1);
   glPopMatrix();
   glPushMatrix();
   glScalef(2.0, 2.0, 2.0);
   glTranslatef(10.0, 13.0, 0.0);
   printStrokedString(test2);
   glPopMatrix();
   glFlush();
}

void reshape(int w, int h)
{
   glViewport(0, 0, (GLsizei) w, (GLsizei) h);
   glMatrixMode (GL_PROJECTION);
   glLoadIdentity ();
   gluOrtho2D (0.0, (GLdouble) w, 0.0, (GLdouble) h);
}

void keyboard(unsigned char key, int x, int y)
{
   switch (key) {
      case ' ':
         glutPostRedisplay();
         break;
      case 27:
         exit(0);
   }
}

/*  Main Loop
 *  Open window with initial window size, title bar, 
 *  RGBA display mode, and handle input events.
 */
int main(int argc, char** argv)
{
   glutInit(&argc, argv);
   glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB);
   glutInitWindowSize (440, 120);
   glutCreateWindow ("stroke");
   init ();
   glutReshapeFunc(reshape);
   glutKeyboardFunc(keyboard);
   glutDisplayFunc(display);
   glutMainLoop();
   return 0;
}