OpenGLUT 0.6.3 development - OpenGLUT: picksquare.c File Reference
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# picksquare.c File Reference

## Detailed Description

Use of multiple names and picking are demonstrated.

A 3x3 grid of squares is drawn.

When the left mouse button is pressed, all squares under the cursor position have their color changed.

    /*
     * Copyright (c) 1993-1997, 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     * Unpublished-- rights reserved under the copyright laws of the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.
     */

    #include <GL/openglut.h>
    #include <stdlib.h>
    #include <stdio.h>

    int board[3][3];   /*  amount of color for each square  */

    /*  Clear color value for every square on the board   */
    void init(void)
    {
       int i, j;
       for (i = 0; i < 3; i++)
          for (j = 0; j < 3; j ++)
             board[i][j] = 0;
       glClearColor (0.0, 0.0, 0.0, 0.0);
    }

    /*  The nine squares are drawn.  In selection mode, each
     *  square is given two names:  one for the row and the
     *  other for the column on the grid.  The color of each
     *  square is determined by its position on the grid, and
     *  the value in the board[][] array.
     */
    void drawSquares(GLenum mode)
    {
       GLuint i, j;
       for (i = 0; i < 3; i++) {
          if (mode == GL_SELECT)
             glLoadName (i);
          for (j = 0; j < 3; j ++) {
             if (mode == GL_SELECT)
                glPushName (j);
             glColor3f ((GLfloat) i/3.0, (GLfloat) j/3.0,
                        (GLfloat) board[i][j]/3.0);
             glRecti (i, j, i+1, j+1);
             if (mode == GL_SELECT)
                glPopName ();
          }
       }
    }

    /*  processHits prints out the contents of the
     *  selection array.
     */
    void processHits (GLint hits, GLuint buffer[])
    {
       GLint i;
       GLuint j, ii = 0, jj = 0, names, *ptr;

       printf ("hits = %d\n", hits);
       ptr = (GLuint *) buffer;
       for (i = 0; i < hits; i++) { /*  for each hit  */
          names = *ptr;
          printf (" number of names for this hit = %d\n", names); ptr++;
          printf("  z1 is %g;", (float) *ptr/0x7fffffff); ptr++;
          printf(" z2 is %g\n", (float) *ptr/0x7fffffff); ptr++;
          printf ("   names are ");
          for (j = 0; j < names; j++) { /*  for each name */
             printf ("%d ", *ptr);
             if (j == 0)  /*  set row and column  */
                ii = *ptr;
             else if (j == 1)
                jj = *ptr;
             ptr++;
          }
          printf ("\n");
          board[ii][jj] = (board[ii][jj] + 1) % 3;
       }
    }

    /*  pickSquares() sets up selection mode, name stack,
     *  and projection matrix for picking.  Then the
     *  objects are drawn.
     */
    #define BUFSIZE 512

    void pickSquares(int button, int state, int x, int y)
    {
       GLuint selectBuf[BUFSIZE];
       GLint hits;
       GLint viewport[4];

       if (button != GLUT_LEFT_BUTTON || state != GLUT_DOWN)
          return;

       glGetIntegerv (GL_VIEWPORT, viewport);

       glSelectBuffer (BUFSIZE, selectBuf);
       (void) glRenderMode (GL_SELECT);

       glInitNames();
       glPushName(0);

       glMatrixMode (GL_PROJECTION);
       glPushMatrix ();
       glLoadIdentity ();
    /*  create 5x5 pixel picking region near cursor location    */
       gluPickMatrix ((GLdouble) x, (GLdouble) (viewport[3] - y),
                      5.0, 5.0, viewport);
       gluOrtho2D (0.0, 3.0, 0.0, 3.0);
       drawSquares (GL_SELECT);

       glMatrixMode (GL_PROJECTION);
       glPopMatrix ();
       glFlush ();

       hits = glRenderMode (GL_RENDER);
       processHits (hits, selectBuf);
       glutPostRedisplay();
    }

    void display(void)
    {
       glClear(GL_COLOR_BUFFER_BIT);
       drawSquares (GL_RENDER);
       glFlush();
    }

    void reshape(int w, int h)
    {
       glViewport(0, 0, w, h);
       glMatrixMode(GL_PROJECTION);
       glLoadIdentity();
       gluOrtho2D (0.0, 3.0, 0.0, 3.0);
       glMatrixMode(GL_MODELVIEW);
       glLoadIdentity();
    }

    /* ARGSUSED1 */
    void keyboard(unsigned char key, int x, int y)
    {
       switch (key) {
          case 27:
             exit(0);
             break;
       }
    }

    /* Main Loop */
    int main(int argc, char** argv)
    {
       glutInit(&argc, argv);
       glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB);
       glutInitWindowSize (100, 100);
       glutInitWindowPosition (100, 100);
       glutCreateWindow (argv[0]);
       init ();
       glutReshapeFunc (reshape);
       glutDisplayFunc(display);
       glutMouseFunc (pickSquares);
       glutKeyboardFunc (keyboard);
       glutMainLoop();
       return 0;
    }

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