text: /* +---------------------------------------------------------------------------+
     |                     Mobile Robot Programming Toolkit (MRPT)               |
     |                          http://www.mrpt.org/                             |
     |                                                                           |
     | Copyright (c) 2005-2018, Individual contributors, see AUTHORS file        |
     | See: http://www.mrpt.org/Authors - All rights reserved.                   |
     | Released under BSD License. See details in http://www.mrpt.org/License    |
     +---------------------------------------------------------------------------+ */
  
  #include <GL/freeglut.h>
  #include "freeglut_internal.h"
  
  /* -- DEFINITIONS ---------------------------------------------------------- */
  
  /*
   * FREEGLUT_MENU_FONT can be any freeglut bitmapped font.
   * (Stroked fonts would not be out of the question, but we'd need to alter
   *  code, since GLUT (hence freeglut) does not quite unify stroked and
   *  bitmapped font handling.)
   * Old UNIX/X11 GLUT (BSD, UNIX, IRIX, LINUX, HPUX, ...) used a system
   * font best approximated by an 18-pixel HELVETICA, I think.  MS-WINDOWS
   * GLUT used something closest to the 8x13 fixed-width font.  (Old
   * GLUT apparently uses host-system menus rather than building its own.
   * freeglut is building its own menus from scratch.)
   *
   * FREEGLUT_MENU_HEIGHT gives the height of ONE menu box.  This should be
   * the distances between two adjacent menu entries.  It should scale
   * automatically with the font choice, so you needn't alter it---unless you
   * use a stroked font.
   *
   * FREEGLUT_MENU_BORDER says how many pixels to allow around the edge of a
   * menu.  (It also seems to be the same as the number of pixels used as
   * a border around *items* to separate them from neighbors.  John says
   * that that wasn't the original intent...if not, perhaps we need another
   * symbolic constant, FREEGLUT_MENU_ITEM_BORDER, or such.)
   */
  #if TARGET_HOST_WIN32 || TARGET_HOST_WINCE
  #define  FREEGLUT_MENU_FONT    GLUT_BITMAP_8_BY_13
  #else
  #define  FREEGLUT_MENU_FONT    GLUT_BITMAP_HELVETICA_18
  #endif
  
  #define  FREEGLUT_MENU_HEIGHT  (glutBitmapHeight(FREEGLUT_MENU_FONT) + \
                                  FREEGLUT_MENU_BORDER)
  #define  FREEGLUT_MENU_BORDER   2
  
  
  /*
   * These variables are for rendering the freeglut menu items.
   *
   * The choices are fore- and background, with and without h for Highlighting.
   * Old GLUT appeared to be system-dependant for its colors (sigh) so we are
   * too.  These variables should be stuffed into global state and initialized
   * via the glutInit*() system.
   */
  #if TARGET_HOST_WIN32 || TARGET_HOST_WINCE
  static float menu_pen_fore  [4] = {0.0f,  0.0f,  0.0f,  1.0f};
  static float menu_pen_back  [4] = {0.85f, 0.85f, 0.85f, 1.0f};
  static float menu_pen_hfore [4] = {1.0f,  1.0f,  1.0f,  1.0f};
  static float menu_pen_hback [4] = {0.15f, 0.15f, 0.45f, 1.0f};
  #else
  static float menu_pen_fore  [4] = {0.0f,  0.0f,  0.0f,  1.0f};
  static float menu_pen_back  [4] = {0.70f, 0.70f, 0.70f, 1.0f};
  static float menu_pen_hfore [4] = {0.0f,  0.0f,  0.0f,  1.0f};
  static float menu_pen_hback [4] = {1.0f,  1.0f,  1.0f,  1.0f};
  #endif
  
  /* -- PRIVATE FUNCTIONS ---------------------------------------------------- */
  
  /*
   * Private function to find a menu entry by index
   */
  static SFG_MenuEntry *fghFindMenuEntry( SFG_Menu* menu, int index )
  {
      SFG_MenuEntry *entry;
      int i = 1;
  
      for( entry = (SFG_MenuEntry *)menu->Entries.First;
           entry;
           entry = (SFG_MenuEntry *)entry->Node.Next )
      {
          if( i == index )
              break;
          ++i;
      }
  
      return entry;
  }
  
  /*
   * Deactivates a menu pointed by the function argument.
   */
  static void fghDeactivateSubMenu( SFG_MenuEntry *menuEntry )
  {
      SFG_MenuEntry *subMenuIter;
      /* Hide the present menu's window */
      fgSetWindow( menuEntry->SubMenu->Window );
      glutHideWindow( );
  
      /* Forget about having that menu active anymore, now: */
      menuEntry->SubMenu->Window->ActiveMenu = NULL;
      menuEntry->SubMenu->IsActive = GL_FALSE;
      menuEntry->SubMenu->ActiveEntry = NULL;
  
      /* Hide all submenu windows, and the root menu's window. */
      for ( subMenuIter = (SFG_MenuEntry *)menuEntry->SubMenu->Entries.First;
            subMenuIter;
            subMenuIter = (SFG_MenuEntry *)subMenuIter->Node.Next )
      {
          subMenuIter->IsActive = GL_FALSE;
  
          /* Is that an active submenu by any case? */
          if( subMenuIter->SubMenu )
              fghDeactivateSubMenu( subMenuIter );
      }
  
      fgSetWindow ( menuEntry->SubMenu->ParentWindow ) ;
  }
  
  /*
   * Private function to get the virtual maximum screen extent
   */
  static GLvoid fghGetVMaxExtent( SFG_Window* window, int* x, int* y )
  {
      if( fgStructure.GameMode )
      {
  #if TARGET_HOST_UNIX_X11
          int wx, wy;
          Window w;
  
          XTranslateCoordinates(
              fgDisplay.Display,
              window->Window.Handle,
              fgDisplay.RootWindow,
              0, 0, &wx, &wy, &w);
  
          *x = fgState.GameModeSize.X + wx;
          *y = fgState.GameModeSize.Y + wy;
  #else
          *x = glutGet ( GLUT_SCREEN_WIDTH );
          *y = glutGet ( GLUT_SCREEN_HEIGHT );
  #endif
      }
      else
      {
          *x = fgDisplay.ScreenWidth;
          *y = fgDisplay.ScreenHeight;
      }
  }
  
  /*
   * Private function to check for the current menu/sub menu activity state
   */
  static GLboolean fghCheckMenuStatus( SFG_Menu* menu )
  {
      SFG_MenuEntry* menuEntry;
      int x, y;
  
      /* First of all check any of the active sub menus... */
      for( menuEntry = (SFG_MenuEntry *)menu->Entries.First;
           menuEntry;
           menuEntry = (SFG_MenuEntry *)menuEntry->Node.Next )
      {
          if( menuEntry->SubMenu && menuEntry->IsActive )
          {
              /*
               * OK, have the sub-menu checked, too. If it returns GL_TRUE, it
               * will mean that it caught the mouse cursor and we do not need
               * to regenerate the activity list, and so our parents do...
               */
              GLboolean return_status;
  
              menuEntry->SubMenu->Window->State.MouseX =
                  menu->Window->State.MouseX + menu->X - menuEntry->SubMenu->X;
              menuEntry->SubMenu->Window->State.MouseY =
                  menu->Window->State.MouseY + menu->Y - menuEntry->SubMenu->Y;
              return_status = fghCheckMenuStatus( menuEntry->SubMenu );
  
              if ( return_status )
                  return GL_TRUE;
          }
      }
  
      /* That much about our sub menus, let's get to checking the current menu: */
      x = menu->Window->State.MouseX;
      y = menu->Window->State.MouseY;
  
      /* Check if the mouse cursor is contained within the current menu box */
      if( ( x >= FREEGLUT_MENU_BORDER ) &&
          ( x < menu->Width  - FREEGLUT_MENU_BORDER ) &&
          ( y >= FREEGLUT_MENU_BORDER ) &&
          ( y < menu->Height - FREEGLUT_MENU_BORDER )  )
      {
          int menuID = ( y - FREEGLUT_MENU_BORDER ) / FREEGLUT_MENU_HEIGHT;
  
          /* The mouse cursor is somewhere over our box, check it out. */
          menuEntry = fghFindMenuEntry( menu, menuID + 1 );
          FREEGLUT_INTERNAL_ERROR_EXIT( menuEntry, "Cannot find menu entry",
                                        "fghCheckMenuStatus" );
  
          menuEntry->IsActive = GL_TRUE;
          menuEntry->Ordinal = menuID;
  
          /*
           * If this is not the same as the last active menu entry, deactivate
           * the previous entry.  Specifically, if the previous active entry
           * was a submenu then deactivate it.
           */
          if( menu->ActiveEntry && ( menuEntry != menu->ActiveEntry ) )
              if( menu->ActiveEntry->SubMenu )
                  fghDeactivateSubMenu( menu->ActiveEntry );
  
          if( menuEntry != menu->ActiveEntry )
          {
              menu->Window->State.Redisplay = GL_TRUE;
              if( menu->ActiveEntry )
                  menu->ActiveEntry->IsActive = GL_FALSE;
          }
  
          menu->ActiveEntry = menuEntry;
          menu->IsActive = GL_TRUE;  /* XXX Do we need this? */
  
          /*
           * OKi, we have marked that entry as active, but it would be also
           * nice to have its contents updated, in case it's a sub menu.
           * Also, ignore the return value of the check function:
           */
          if( menuEntry->SubMenu )
          {
              if ( ! menuEntry->SubMenu->IsActive )
              {
                  int max_x, max_y;
                  SFG_Window *current_window = fgStructure.CurrentWindow;
  
                  /* Set up the initial menu position now... */
                  menuEntry->SubMenu->IsActive = GL_TRUE;
  
                  /* Set up the initial submenu position now: */
                  fghGetVMaxExtent(menu->ParentWindow, &max_x, &max_y);
                  menuEntry->SubMenu->X = menu->X + menu->Width;
                  menuEntry->SubMenu->Y = menu->Y +
                      menuEntry->Ordinal * FREEGLUT_MENU_HEIGHT;
  
                  if( menuEntry->SubMenu->X + menuEntry->SubMenu->Width > max_x )
                      menuEntry->SubMenu->X = menu->X - menuEntry->SubMenu->Width;
  
                  if( menuEntry->SubMenu->Y + menuEntry->SubMenu->Height > max_y )
                      menuEntry->SubMenu->Y -= ( menuEntry->SubMenu->Height -
                                                 FREEGLUT_MENU_HEIGHT -
                                                 2 * FREEGLUT_MENU_BORDER );
  
                  fgSetWindow( menuEntry->SubMenu->Window );
                  glutPositionWindow( menuEntry->SubMenu->X,
                                      menuEntry->SubMenu->Y );
                  glutReshapeWindow( menuEntry->SubMenu->Width,
                                     menuEntry->SubMenu->Height );
                  glutPopWindow( );
                  glutShowWindow( );
                  menuEntry->SubMenu->Window->ActiveMenu = menuEntry->SubMenu;
                  fgSetWindow( current_window );
                  menuEntry->SubMenu->Window->State.MouseX =
                      x + menu->X - menuEntry->SubMenu->X;
                  menuEntry->SubMenu->Window->State.MouseY =
                      y + menu->Y - menuEntry->SubMenu->Y;
                  fghCheckMenuStatus( menuEntry->SubMenu );
              }
  
              /* Activate it because its parent entry is active */
              menuEntry->SubMenu->IsActive = GL_TRUE;  /* XXX Do we need this? */
          }
  
          /* Report back that we have caught the menu cursor */
          return GL_TRUE;
      }
  
      /* Looks like the menu cursor is somewhere else... */
      if( menu->ActiveEntry && menu->ActiveEntry->IsActive &&
          ( !menu->ActiveEntry->SubMenu ||
            !menu->ActiveEntry->SubMenu->IsActive ) )
      {
          menu->Window->State.Redisplay = GL_TRUE;
          menu->ActiveEntry->IsActive = GL_FALSE;
          menu->ActiveEntry = NULL;
      }
  
      return GL_FALSE;
  }
  
  /*
   * Displays a menu box and all of its submenus (if they are active)
   */
  static void fghDisplayMenuBox( SFG_Menu* menu )
  {
      SFG_MenuEntry *menuEntry;
      int i;
      int border = FREEGLUT_MENU_BORDER;
  
      /*
       * Have the menu box drawn first. The +- values are
       * here just to make it more nice-looking...
       */
      /* a non-black dark version of the below. */
      glColor4f( 1.0f, 1.0f, 1.0f, 1.0f );
      glBegin( GL_QUAD_STRIP );
          glVertex2i( menu->Width         , 0                    );
          glVertex2i( menu->Width - border,                border);
          glVertex2i( 0                   , 0                    );
          glVertex2i(               border,                border);
          glVertex2i( 0                   , menu->Height         );
          glVertex2i(               border, menu->Height - border);
      glEnd( );
  
      /* a non-black dark version of the below. */
      glColor4f( 0.5f, 0.5f, 0.5f, 1.0f );
      glBegin( GL_QUAD_STRIP );
          glVertex2i( 0                   , menu->Height         );
          glVertex2i(               border, menu->Height - border);
          glVertex2i( menu->Width         , menu->Height         );
          glVertex2i( menu->Width - border, menu->Height - border);
          glVertex2i( menu->Width         , 0                    );
          glVertex2i( menu->Width - border,                border);
      glEnd( );
  
      glColor4fv( menu_pen_back );
      glBegin( GL_QUADS );
          glVertex2i(               border,                border);
          glVertex2i( menu->Width - border,                border);
          glVertex2i( menu->Width - border, menu->Height - border);
          glVertex2i(               border, menu->Height - border);
      glEnd( );
  
      /* Check if any of the submenus is currently active... */
      for( menuEntry = (SFG_MenuEntry *)menu->Entries.First;
           menuEntry;
           menuEntry = (SFG_MenuEntry *)menuEntry->Node.Next )
      {
          /* Has the menu been marked as active, maybe? */
          if( menuEntry->IsActive )
          {
              /*
               * That's truly right, and we need to have it highlighted.
               * There is an assumption that mouse cursor didn't move
               * since the last check of menu activity state:
               */
              int menuID = menuEntry->Ordinal;
  
              /* So have the highlight drawn... */
              glColor4fv( menu_pen_hback );
              glBegin( GL_QUADS );
                  glVertex2i( border,
                              (menuID + 0)*FREEGLUT_MENU_HEIGHT + border );
                  glVertex2i( menu->Width - border,
                              (menuID + 0)*FREEGLUT_MENU_HEIGHT + border );
                  glVertex2i( menu->Width - border,
                              (menuID + 1)*FREEGLUT_MENU_HEIGHT + border );
                  glVertex2i( border,
                              (menuID + 1)*FREEGLUT_MENU_HEIGHT + border );
              glEnd( );
          }
      }
  
      /* Print the menu entries now... */
  
      glColor4fv( menu_pen_fore );
  
      for( menuEntry = (SFG_MenuEntry *)menu->Entries.First, i = 0;
           menuEntry;
           menuEntry = (SFG_MenuEntry *)menuEntry->Node.Next, ++i )
      {
          /* If the menu entry is active, set the color to white */
          if( menuEntry->IsActive )
              glColor4fv( menu_pen_hfore );
  
          /* Move the raster into position... */
          /* Try to center the text - JCJ 31 July 2003*/
          glRasterPos2i(
              2 * border,
              ( i + 1 )*FREEGLUT_MENU_HEIGHT -
              ( int )( FREEGLUT_MENU_HEIGHT*0.3 - border )
          );
  
          /* Have the label drawn, character after character: */
          glutBitmapString( FREEGLUT_MENU_FONT,
                            (unsigned char *)menuEntry->Text);
  
          /* If it's a submenu, draw a right arrow */
          if( menuEntry->SubMenu )
          {
              int width = glutBitmapWidth( FREEGLUT_MENU_FONT, '_' );
              int x_base = menu->Width - 2 - width;
              int y_base = i*FREEGLUT_MENU_HEIGHT + border;
              glBegin( GL_TRIANGLES );
                  glVertex2i( x_base, y_base + 2*border);
                  glVertex2i( menu->Width - 2, y_base +
                              ( FREEGLUT_MENU_HEIGHT + border) / 2 );
                  glVertex2i( x_base, y_base + FREEGLUT_MENU_HEIGHT - border );
              glEnd( );
          }
  
          /* If the menu entry is active, reset the color */
          if( menuEntry->IsActive )
              glColor4fv( menu_pen_fore );
      }
  }
  
  /*
   * Private static function to set the parent window of a submenu and all
   * of its submenus
   */
  static void fghSetMenuParentWindow( SFG_Window *window, SFG_Menu *menu )
  {
      SFG_MenuEntry *menuEntry;
  
      menu->ParentWindow = window;
  
      for( menuEntry = ( SFG_MenuEntry * )menu->Entries.First;
           menuEntry;
           menuEntry = ( SFG_MenuEntry * )menuEntry->Node.Next )
          if( menuEntry->SubMenu )
              fghSetMenuParentWindow( window, menuEntry->SubMenu );
  }
  
  /*
   * Function to check for menu entry selection on menu deactivation
   */
  static void fghExecuteMenuCallback( SFG_Menu* menu )
  {
      SFG_MenuEntry *menuEntry;
  
      /* First of all check any of the active sub menus... */
      for( menuEntry = (SFG_MenuEntry *)menu->Entries.First;
           menuEntry;
           menuEntry = (SFG_MenuEntry *)menuEntry->Node.Next)
      {
          if( menuEntry->IsActive )
          {
              if( menuEntry->SubMenu )
                  fghExecuteMenuCallback( menuEntry->SubMenu );
              else
                  if( menu->Callback )
                  {
                      SFG_Menu *save_menu = fgStructure.CurrentMenu;
                      fgStructure.CurrentMenu = menu;
                      menu->Callback( menuEntry->ID );
                      fgStructure.CurrentMenu = save_menu;
                  }
  
              return;
          }
      }
  }
  
  
  /*
   * Displays the currently active menu for the current window
   */
  void fgDisplayMenu( void )
  {
      SFG_Window* window = fgStructure.CurrentWindow;
      SFG_Menu* menu = NULL;
  
      FREEGLUT_INTERNAL_ERROR_EXIT ( fgStructure.CurrentWindow, "Displaying menu in nonexistent window",
                                     "fgDisplayMenu" );
  
      /* Check if there is an active menu attached to this window... */
      menu = window->ActiveMenu;
      freeglut_return_if_fail( menu );
  
      fgSetWindow( menu->Window );
  
      glPushAttrib( GL_DEPTH_BUFFER_BIT | GL_TEXTURE_BIT | GL_LIGHTING_BIT |
                    GL_POLYGON_BIT );
  
      glDisable( GL_DEPTH_TEST );
      glDisable( GL_TEXTURE_2D );
      glDisable( GL_LIGHTING   );
      glDisable( GL_CULL_FACE  );
  
      glMatrixMode( GL_PROJECTION );
      glPushMatrix( );
      glLoadIdentity( );
      glOrtho(
           0, glutGet( GLUT_WINDOW_WIDTH  ),
           glutGet( GLUT_WINDOW_HEIGHT ), 0,
          -1, 1
      );
  
      glMatrixMode( GL_MODELVIEW );
      glPushMatrix( );
      glLoadIdentity( );
  
      fghDisplayMenuBox( menu );
  
      glPopAttrib( );
  
      glMatrixMode( GL_PROJECTION );
      glPopMatrix( );
      glMatrixMode( GL_MODELVIEW );
      glPopMatrix( );
  
      glutSwapBuffers( );
  
      fgSetWindow ( window );
  }
  
  /*
   * Activates a menu pointed by the function argument
   */
  static void fghActivateMenu( SFG_Window* window, int button )
  {
      int max_x, max_y;
  
      /* We'll be referencing this menu a lot, so remember its address: */
      SFG_Menu* menu = window->Menu[ button ];
      SFG_Window* current_window = fgStructure.CurrentWindow;
  
      /* If the menu is already active in another window, deactivate it there */
      if ( menu->ParentWindow )
        menu->ParentWindow->ActiveMenu = NULL ;
  
      /* Mark the menu as active, so that it gets displayed: */
      window->ActiveMenu = menu;
      menu->IsActive = GL_TRUE;
      fghSetMenuParentWindow ( window, menu );
      fgState.ActiveMenus++;
  
      /* Set up the initial menu position now: */
      fghGetVMaxExtent(menu->ParentWindow, &max_x, &max_y);
      fgSetWindow( window );
      menu->X = window->State.MouseX + glutGet( GLUT_WINDOW_X );
      menu->Y = window->State.MouseY + glutGet( GLUT_WINDOW_Y );
  
      if( menu->X + menu->Width > max_x )
          menu->X -=menu->Width;
  
      if( menu->Y + menu->Height > max_y )
          menu->Y -=menu->Height;
  
      menu->Window->State.MouseX =
          window->State.MouseX + glutGet( GLUT_WINDOW_X ) - menu->X;
      menu->Window->State.MouseY =
          window->State.MouseY + glutGet( GLUT_WINDOW_Y ) - menu->Y;
  
      fgSetWindow( menu->Window );
      glutPositionWindow( menu->X, menu->Y );
      glutReshapeWindow( menu->Width, menu->Height );
      glutPopWindow( );
      glutShowWindow( );
      menu->Window->ActiveMenu = menu;
      fghCheckMenuStatus( menu );
      fgSetWindow( current_window );
  }
  
  /*
   * Update Highlight states of the menu
   *
   * Current mouse position is in menu->Window->State.MouseX/Y.
   */
  void fgUpdateMenuHighlight ( SFG_Menu *menu )
  {
      fghCheckMenuStatus( menu );
  }
  
  /*
   * Check whether an active menu absorbs a mouse click
   */
  GLboolean fgCheckActiveMenu ( SFG_Window *window, int button, GLboolean pressed,
                                int mouse_x, int mouse_y )
  {
      /*
       * Near as I can tell, this is the menu behaviour:
       *  - Down-click the menu button, menu not active:  activate
       *    the menu with its upper left-hand corner at the mouse
       *    location.
       *  - Down-click any button outside the menu, menu active:
       *    deactivate the menu
       *  - Down-click any button inside the menu, menu active:
       *    select the menu entry and deactivate the menu
       *  - Up-click the menu button, menu not active:  nothing happens
       *  - Up-click the menu button outside the menu, menu active:
       *    nothing happens
       *  - Up-click the menu button inside the menu, menu active:
       *    select the menu entry and deactivate the menu
       * Since menus can have submenus, we need to check this recursively.
       */
      if( window->ActiveMenu )
      {
          if( window == window->ActiveMenu->ParentWindow )
          {
              window->ActiveMenu->Window->State.MouseX =
                                         mouse_x - window->ActiveMenu->X;
              window->ActiveMenu->Window->State.MouseY =
                                         mouse_y - window->ActiveMenu->Y;
          }
  
          /* In the menu, invoke the callback and deactivate the menu */
          if( fghCheckMenuStatus( window->ActiveMenu ) )
          {
              /*
               * Save the current window and menu and set the current
               * window to the window whose menu this is
               */
              SFG_Window *save_window = fgStructure.CurrentWindow;
              SFG_Menu *save_menu = fgStructure.CurrentMenu;
              SFG_Window *parent_window = window->ActiveMenu->ParentWindow;
              fgSetWindow( parent_window );
              fgStructure.CurrentMenu = window->ActiveMenu;
  
              /* Execute the menu callback */
              fghExecuteMenuCallback( window->ActiveMenu );
              fgDeactivateMenu( parent_window );
  
              /* Restore the current window and menu */
              fgSetWindow( save_window );
              fgStructure.CurrentMenu = save_menu;
          }
          else if( pressed )
              /*
               * Outside the menu, deactivate if it's a downclick
               *
               * XXX This isn't enough.  A downclick outside of
               * XXX the interior of our freeglut windows should also
               * XXX deactivate the menu.  This is more complicated.
               */
              fgDeactivateMenu( window->ActiveMenu->ParentWindow );
  
          /*
           * XXX Why does an active menu require a redisplay at
           * XXX this point?  If this can come out cleanly, then
           * XXX it probably should do so; if not, a comment should
           * XXX explain it.
           */
          if( ! window->IsMenu )
              window->State.Redisplay = GL_TRUE;
  
          return GL_TRUE;
      }
  
      /* No active menu, let's check whether we need to activate one. */
      if( ( 0 <= button ) &&
          ( FREEGLUT_MAX_MENUS > button ) &&
          ( window->Menu[ button ] ) &&
          pressed )
      {
          /* XXX Posting a requisite Redisplay seems bogus. */
          window->State.Redisplay = GL_TRUE;
          fghActivateMenu( window, button );
          return GL_TRUE;
      }
  
      return GL_FALSE;
  }
  
  /*
   * Deactivates a menu pointed by the function argument.
   */
  void fgDeactivateMenu( SFG_Window *window )
  {
      SFG_Window *parent_window = NULL;
  
      /* Check if there is an active menu attached to this window... */
      SFG_Menu* menu = window->ActiveMenu;
      SFG_MenuEntry *menuEntry;
  
      /* Did we find an active window? */
      freeglut_return_if_fail( menu );
  
      parent_window = menu->ParentWindow;
  
      /* Hide the present menu's window */
      fgSetWindow( menu->Window );
      glutHideWindow( );
  
      /* Forget about having that menu active anymore, now: */
      menu->Window->ActiveMenu = NULL;
      menu->ParentWindow->ActiveMenu = NULL;
      fghSetMenuParentWindow ( NULL, menu );
      menu->IsActive = GL_FALSE;
      menu->ActiveEntry = NULL;
  
      fgState.ActiveMenus--;
  
      /* Hide all submenu windows, and the root menu's window. */
      for ( menuEntry = ( SFG_MenuEntry * )menu->Entries.First;
            menuEntry;
            menuEntry = ( SFG_MenuEntry * )menuEntry->Node.Next )
      {
          menuEntry->IsActive = GL_FALSE;
  
          /* Is that an active submenu by any case? */
          if( menuEntry->SubMenu )
              fghDeactivateSubMenu( menuEntry );
      }
  
      fgSetWindow ( parent_window ) ;
  }
  
  /*
   * Recalculates current menu's box size
   */
  void fghCalculateMenuBoxSize( void )
  {
      SFG_MenuEntry* menuEntry;
      int width = 0, height = 0;
  
      /* Make sure there is a current menu set */
      freeglut_return_if_fail( fgStructure.CurrentMenu );
  
      /* The menu's box size depends on the menu entries: */
      for( menuEntry = ( SFG_MenuEntry * )fgStructure.CurrentMenu->Entries.First;
           menuEntry;
           menuEntry = ( SFG_MenuEntry * )menuEntry->Node.Next )
      {
          /* Update the menu entry's width value */
          menuEntry->Width = glutBitmapLength(
              FREEGLUT_MENU_FONT,
              (unsigned char *)menuEntry->Text
          );
  
          /*
           * If the entry is a submenu, then it needs to be wider to
           * accomodate the arrow. JCJ 31 July 2003
           */
          if (menuEntry->SubMenu )
              menuEntry->Width += glutBitmapLength(
                  FREEGLUT_MENU_FONT,
                  (unsigned char *)"_"
              );
  
          /* Check if it's the biggest we've found */
          if( menuEntry->Width > width )
              width = menuEntry->Width;
  
          height += FREEGLUT_MENU_HEIGHT;
      }
  
      /* Store the menu's box size now: */
      fgStructure.CurrentMenu->Height = height + 2 * FREEGLUT_MENU_BORDER;
      fgStructure.CurrentMenu->Width  = width  + 4 * FREEGLUT_MENU_BORDER;
  }
  
  
  /* -- INTERFACE FUNCTIONS -------------------------------------------------- */
  
  /*
   * Creates a new menu object, adding it to the freeglut structure
   */
  int FGAPIENTRY glutCreateMenu( void(* callback)( int ) )
  {
      /* The menu object creation code resides in freeglut_structure.c */
      FREEGLUT_EXIT_IF_NOT_INITIALISED ( "glutCreateMenu" );
      return fgCreateMenu( callback )->ID;
  }
  
  /*
   * Destroys a menu object, removing all references to it
   */
  void FGAPIENTRY glutDestroyMenu( int menuID )
  {
      SFG_Menu* menu;
  
      FREEGLUT_EXIT_IF_NOT_INITIALISED ( "glutDestroyMenu" );
      menu = fgMenuByID( menuID );
  
      freeglut_return_if_fail( menu );
  
      /* The menu object destruction code resides in freeglut_structure.c */
      fgDestroyMenu( menu );
  }
  
  /*
   * Returns the ID number of the currently active menu
   */
  int FGAPIENTRY glutGetMenu( void )
  {
      FREEGLUT_EXIT_IF_NOT_INITIALISED ( "glutGetMenu" );
  
      if( fgStructure.CurrentMenu )
          return fgStructure.CurrentMenu->ID;
  
      return 0;
  }
  
  /*
   * Sets the current menu given its menu ID
   */
  void FGAPIENTRY glutSetMenu( int menuID )
  {
      SFG_Menu* menu;
  
      FREEGLUT_EXIT_IF_NOT_INITIALISED ( "glutSetMenu" );
      menu = fgMenuByID( menuID );
  
      freeglut_return_if_fail( menu );
  
      fgStructure.CurrentMenu = menu;
  }
  
  /*
   * Adds a menu entry to the bottom of the current menu
   */
  void FGAPIENTRY glutAddMenuEntry( const char* label, int value )
  {
      SFG_MenuEntry* menuEntry;
      FREEGLUT_EXIT_IF_NOT_INITIALISED ( "glutAddMenuEntry" );
      menuEntry = (SFG_MenuEntry *)calloc( sizeof(SFG_MenuEntry), 1 );
      freeglut_return_if_fail( fgStructure.CurrentMenu );
  
      menuEntry->Text = strdup( label );
      menuEntry->ID   = value;
  
      /* Have the new menu entry attached to the current menu */
      fgListAppend( &fgStructure.CurrentMenu->Entries, &menuEntry->Node );
  
      fghCalculateMenuBoxSize( );
  }
  
  /*
   * Add a sub menu to the bottom of the current menu
   */
  void FGAPIENTRY glutAddSubMenu( const char *label, int subMenuID )
  {
      SFG_MenuEntry *menuEntry;
      SFG_Menu *subMenu;
  
      FREEGLUT_EXIT_IF_NOT_INITIALISED ( "glutAddSubMenu" );
      menuEntry = ( SFG_MenuEntry * )calloc( sizeof( SFG_MenuEntry ), 1 );
      subMenu = fgMenuByID( subMenuID );
  
      freeglut_return_if_fail( fgStructure.CurrentMenu );
      freeglut_return_if_fail( subMenu );
  
      menuEntry->Text    = strdup( label );
      menuEntry->SubMenu = subMenu;
      menuEntry->ID      = -1;
  
      fgListAppend( &fgStructure.CurrentMenu->Entries, &menuEntry->Node );
      fghCalculateMenuBoxSize( );
  }
  
  /*
   * Changes the specified menu item in the current menu into a menu entry
   */
  void FGAPIENTRY glutChangeToMenuEntry( int item, const char* label, int value )
  {
      SFG_MenuEntry* menuEntry = NULL;
  
      FREEGLUT_EXIT_IF_NOT_INITIALISED ( "glutChangeToMenuEntry" );
      freeglut_return_if_fail( fgStructure.CurrentMenu );
  
      /* Get n-th menu entry in the current menu, starting from one: */
      menuEntry = fghFindMenuEntry( fgStructure.CurrentMenu, item );
  
      freeglut_return_if_fail( menuEntry );
  
      /* We want it to become a normal menu entry, so: */
      if( menuEntry->Text )
          free( menuEntry->Text );
  
      menuEntry->Text    = strdup( label );
      menuEntry->ID      = value;
      menuEntry->SubMenu = NULL;
      fghCalculateMenuBoxSize( );
  }
  
  /*
   * Changes the specified menu item in the current menu into a sub-menu trigger.
   */
  void FGAPIENTRY glutChangeToSubMenu( int item, const char* label,
                                       int subMenuID )
  {
      SFG_Menu*      subMenu;
      SFG_MenuEntry* menuEntry;
  
      FREEGLUT_EXIT_IF_NOT_INITIALISED ( "glutChangeToSubMenu" );
      subMenu = fgMenuByID( subMenuID );
      menuEntry = NULL;
  
      freeglut_return_if_fail( fgStructure.CurrentMenu );
      freeglut_return_if_fail( subMenu );
  
      /* Get n-th menu entry in the current menu, starting from one: */
      menuEntry = fghFindMenuEntry( fgStructure.CurrentMenu, item );
  
      freeglut_return_if_fail( menuEntry );
  
      /* We want it to become a sub menu entry, so: */
      if( menuEntry->Text )
          free( menuEntry->Text );
  
      menuEntry->Text    = strdup( label );
      menuEntry->SubMenu = subMenu;
      menuEntry->ID      = -1;
      fghCalculateMenuBoxSize( );
  }
  
  /*
   * Removes the specified menu item from the current menu
   */
  void FGAPIENTRY glutRemoveMenuItem( int item )
  {
      SFG_MenuEntry* menuEntry;
  
      FREEGLUT_EXIT_IF_NOT_INITIALISED ( "glutRemoveMenuItem" );
      freeglut_return_if_fail( fgStructure.CurrentMenu );
  
      /* Get n-th menu entry in the current menu, starting from one: */
      menuEntry = fghFindMenuEntry( fgStructure.CurrentMenu, item );
  
      freeglut_return_if_fail( menuEntry );
  
      fgListRemove( &fgStructure.CurrentMenu->Entries, &menuEntry->Node );
      if ( menuEntry->Text )
        free( menuEntry->Text );
  
      free( menuEntry );
      fghCalculateMenuBoxSize( );
  }
  
  /*
   * Attaches a menu to the current window
   */
  void FGAPIENTRY glutAttachMenu( int button )
  {
      FREEGLUT_EXIT_IF_NOT_INITIALISED ( "glutAttachMenu" );
  
      freeglut_return_if_fail( fgStructure.CurrentWindow );
      freeglut_return_if_fail( fgStructure.CurrentMenu );
  
      freeglut_return_if_fail( button >= 0 );
      freeglut_return_if_fail( button < FREEGLUT_MAX_MENUS );
  
      fgStructure.CurrentWindow->Menu[ button ] = fgStructure.CurrentMenu;
  }
  
  /*
   * Detaches a menu from the current window
   */
  void FGAPIENTRY glutDetachMenu( int button )
  {
      FREEGLUT_EXIT_IF_NOT_INITIALISED ( "glutDetachMenu" );
  
      freeglut_return_if_fail( fgStructure.CurrentWindow );
      freeglut_return_if_fail( fgStructure.CurrentMenu );
  
      freeglut_return_if_fail( button >= 0 );
      freeglut_return_if_fail( button < FREEGLUT_MAX_MENUS );
  
      fgStructure.CurrentWindow->Menu[ button ] = NULL;
  }
  
  /*
   * A.Donev: Set and retrieve the menu's user data
   */
  void* FGAPIENTRY glutGetMenuData( void )
  {
      FREEGLUT_EXIT_IF_NOT_INITIALISED ( "glutGetMenuData" );
      return fgStructure.CurrentMenu->UserData;
  }
  
  void FGAPIENTRY glutSetMenuData(void* data)
  {
      FREEGLUT_EXIT_IF_NOT_INITIALISED ( "glutSetMenuData" );
      fgStructure.CurrentMenu->UserData=data;
  }
  
  /*** END OF FILE ***/
  