#
# Copyright (c) Mark J. Kilgard, 1994. */
#
#
# (c) Copyright 1993, 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# Unpublished-- rights reserved under the copyright laws of the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(TM) is a trademark of Silicon Graphics, Inc.
#
#  pickdepth.c
#  Picking is demonstrated in this program.  In
#  rendering mode, three overlapping rectangles are
#  drawn.  When the left mouse button is pressed,
#  selection mode is entered with the picking matrix.
#  Rectangles which are drawn under the cursor position
#  are "picked."  Pay special attention to the depth
#  value range, which is returned.
require 'opengl'
include Gl,Glu,Glut

def myinit
  glClearColor(0.0, 0.0, 0.0, 0.0)
  glDepthFunc(GL_LESS)
  glEnable(GL_DEPTH_TEST)
  glShadeModel(GL_FLAT)
  glDepthRange(0.0, 1.0)  #/* The default z mapping */
end

# The three rectangles are drawn.  In selection mode,
# each rectangle is given the same name.  Note that
# each rectangle is drawn with a different z value.
def drawRects(mode)
  if (mode == GL_SELECT)
    glLoadName(1)
  end
  glBegin(GL_QUADS)
  glColor(1.0, 1.0, 0.0)
  glVertex(2, 0, 0)
  glVertex(2, 6, 0)
  glVertex(6, 6, 0)
  glVertex(6, 0, 0)
  glEnd()
  if (mode == GL_SELECT)
    glLoadName(2)
  end
  glBegin(GL_QUADS)
  glColor(0.0, 1.0, 1.0)
  glVertex(3, 2, -1)
  glVertex(3, 8, -1)
  glVertex(8, 8, -1)
  glVertex(8, 2, -1)
  glEnd()
  if (mode == GL_SELECT)
    glLoadName(3)
  end
  glBegin(GL_QUADS)
  glColor(1.0, 0.0, 1.0)
  glVertex(0, 2, -2)
  glVertex(0, 7, -2)
  glVertex(5, 7, -2)
  glVertex(5, 2, -2)
  glEnd()
end

# processHits() prints out the contents of the
# selection array.
def processHits(hits, buffer)
  printf("hits = %d\n", hits)
  ptr = buffer.unpack("I*")
  p = 0
  for i in 0...hits   # for each hit
    names = ptr[p]
    printf(" number of names for hit = %d\n", names); p+=1
    printf("  z1 is %g",  ptr[p].to_f/0xffffffff); p+=1
    printf(" z2 is %g\n",  ptr[p].to_f/0xffffffff); p+=1
    printf("   the name is ")
    for j in 0...names  # for each name
      printf("%d ", ptr[p]) ; p+=1
    end
    printf("\n")
  end
end

# pickRects() sets up selection mode, name stack,
# and projection matrix for picking.  Then the objects
# are drawn.
BUFSIZE=512

pickRects = proc do |button, state, x, y|
  if (button == GLUT_LEFT_BUTTON && state == GLUT_DOWN)
    viewport = glGetDoublev(GL_VIEWPORT)

    selectBuf = glSelectBuffer(BUFSIZE)
    glRenderMode(GL_SELECT)

    glInitNames()
    glPushName(~0)

    glMatrixMode(GL_PROJECTION)
    glPushMatrix()
    glLoadIdentity()
    # create 5x5 pixel picking region near cursor location
    gluPickMatrix( x, viewport[3] - y, 5.0, 5.0, viewport)
    glOrtho(0.0, 8.0, 0.0, 8.0, -0.5, 2.5)
    drawRects(GL_SELECT)
    glPopMatrix()
    glFlush()

    hits = glRenderMode(GL_RENDER)
    processHits(hits, selectBuf)
  end
end

display = proc do
  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)
  drawRects(GL_RENDER)
  glutSwapBuffers()
end

myReshape = proc do |w, h|
  glViewport(0, 0, w, h)
  glMatrixMode(GL_PROJECTION)
  glLoadIdentity()
  glOrtho(0.0, 8.0, 0.0, 8.0, -0.5, 2.5)
  glMatrixMode(GL_MODELVIEW)
  glLoadIdentity()
end

keyboard = Proc.new do |key, x, y|
  case (key)
    when ?\e
    exit(0)
  end
end

# Main Loop
# Open window with initial window size, title bar,
# RGBA display mode, depth buffer, and handle input events.
glutInitWindowSize(500, 500)
glutInitWindowPosition(100, 100)
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH)
glutInit()
glutCreateWindow()
myinit()
glutMouseFunc(pickRects)
glutReshapeFunc(myReshape)
glutDisplayFunc(display)
glutKeyboardFunc(keyboard)
glutMainLoop()
