/* 
 * 
 * Released under the MIT License. http://www.opensource.org/licenses/mit-license.php
 * 
 * Works for 
 *   - IE6+ (Windows), 
 *   - Firefox 3.5+ (Windows, Mac, Linux), 
 *   - Safari 4+ (Windows, Mac OS X), 
 *   - Chrome 3.0+ (Windows).
 * Opera 10.10 and under reports unknown support for font-smoothing.
 * 
 * 
 * METHODS
 * -------
 * 
 * hasSmoothing() returns:
 *     true if font smoothing is enabled
 *     false if font smoothing isn't enabled
 *     null if it cannot detect if it's on or not.
 *     
 * addClasses() adds the following classes to the html tag:
 *     "hasFontSmoothing-true" if font smoothing is enabled
 *     "hasFontSmoothing-false" if it isn't
 *     "hasFontSmoothing-unknown" if it cannot detect it.
 *       
 */

var TypeHelpers = new function(){
   var me = this;
   
   me.hasSmoothing = function(){
   
      // IE has screen.fontSmoothingEnabled - sweet!      
      if (typeof(screen.fontSmoothingEnabled) != "undefined") {
         return screen.fontSmoothingEnabled;  
      } else {
	  	
         try {
          
            // Create a 35x35 Canvas block.
            var canvasNode = document.createElement("canvas");
            canvasNode.width = "35";
            canvasNode.height = "35"
            
            // We must put this node into the body, otherwise 
            // Safari Windows does not report correctly.
            canvasNode.style.display = "none";
            document.body.appendChild(canvasNode);
            var ctx = canvasNode.getContext("2d");
            
            // draw a black letter "O", 32px Arial.
            ctx.textBaseline = "top";
            ctx.font = "32px Arial";
            ctx.fillStyle = "black";
            ctx.strokeStyle = "black";
            
            ctx.fillText("O", 0, 0);
            
            // start at (8,1) and search the canvas from left to right,
            // top to bottom to see if we can find a non-black pixel.  If
            // so we return true.
            for (var j = 8; j <= 32; j++) {
               for (var i = 1; i <= 32; i++) {
               
                  var imageData = ctx.getImageData(i, j, 1, 1).data;
                  var alpha = imageData[3];
                  
                  if (alpha != 255 && alpha != 0) {
                     return true; // font-smoothing must be on.
                  }
               }
               
            }
         
            // didn't find any non-black pixels - return false.
            return false;
         } 
         catch (ex) {
            // Something went wrong (for example, Opera cannot use the
            // canvas fillText() method.  Return null (unknown).
            return null;
         }
      }
   }
   
   me.insertClasses = function(){
      var result = me.hasSmoothing();
      var htmlNode = document.getElementsByTagName("html")[0];
      if (result == true) {
         htmlNode.className += " hasFontSmoothing-true";
      } else if (result == false) {
            htmlNode.className += " hasFontSmoothing-false";
      } else { // result == null
            htmlNode.className += " hasFontSmoothing-unknown";
      }
   }
   
}


// Insert the hasFontSmoothing CSS classes after document has loaded
jQuery(document).ready(function($) {
    TypeHelpers.insertClasses()
});