//

// javascript for MIT Course Catalogue home page

//







//// code for pop-up menus

// NOTE: function names have been abbreviated for this site - sme(), sdhm(), cdhm()



// how it works:

//  When the mouse passes over one of the main navigation buttons, it calls

//   show_menu_exclusive() to open that buttons's pop-up menu,

//   and close any others that might be open.

//  When the mouse leaves the nav button, it starts a delayed closing of that

//   pop-up menu by calling start_delayed_hide_menu(). The closing

//   is delayed because the mouse might be entering the pop-up menu. If not, then the menu

//   will either be closed by the delayed call to do_delayed_hide_menu(), or by entering

//   a different navigation button.

//  When the mouse enters a pop-up menu button, it cancels the delayed close of that

//   pop-up menu with cancel_delayed_hide_menu().

//  When the mouse leaves a pop-up menu button, it starts the delayed close.

//



//// globals



// variable records which menu is currently open

var open_menu = "";



// timer for delayed hide

var timerid = null;



//// functions



// show main nav mouseover and corresponding pop-up menu (immediately hide previous, if any)

//

//function show_menu_exclusive(menuname) {

function sme(menuname) {



  if (timerid != null) {        // cancel any delayed hides

    clearTimeout (timerid);

    timerid = null;

  }



  if (open_menu == menuname)  // return if this menu already open

    return;



  if (open_menu != "") {      // restore main navigation button

    // find button object

    var oldnavobj = MM_findObj(open_menu);

    // set original background color

    if (oldnavobj != null) {

      oldnavobj.className = "off";

    }

    // hide the old pop-up menu

    var oldmenu = "menu" + open_menu;

    MM_showHideLayers(oldmenu,'','hide')

  }



  // set new button rollover and show pop-up menu



  if (menuname != "") {

    // find image object

    var navobj = MM_findObj(menuname);

    if (navobj != null) {

      navobj.className = "on";

    }

    // show the new pop-up menu

    var menulayer = "menu" + menuname;

    MM_showHideLayers(menulayer,'','show')

  }



  // record the open menu

  open_menu = menuname;

}



// start delayed main nav image restoration and pop-up menu hiding

//

//function start_delayed_hide_menu() {

function sdhm() {

  timerid = setTimeout("do_delayed_hide_menu()", 50); // last arg is delay in milliseconds

}



// cancel delayed main nav image restoration and pop-up menu hiding

//

//function cancel_delayed_hide_menu() {

function cdhm() {

  if (timerid != null) {

    clearTimeout (timerid);

    timerid = null;

  }

}



// perform delayed main nav image restoration and pop-up menu hiding

//

function do_delayed_hide_menu() {

//  show_menu_exclusive("");

  sme("");

}