dojo.provide("dojox.html.metrics");

(function(){
	var dhm = dojox.html.metrics;

	//	derived from Morris John's emResized measurer
	dhm.getFontMeasurements = function(){
		//	summary
		//	Returns an object that has pixel equivilents of standard font size values.
		var heights = {
			'1em':0, '1ex':0, '100%':0, '12pt':0, '16px':0, 'xx-small':0, 'x-small':0,
			'small':0, 'medium':0, 'large':0, 'x-large':0, 'xx-large':0
		};
	
		if(dojo.isIE){
			//	we do a font-size fix if and only if one isn't applied already.
			//	NOTE: If someone set the fontSize on the HTML Element, this will kill it.
			dojo.doc.documentElement.style.fontSize="100%";
		}
	
		//	set up the measuring node.
		var div=dojo.doc.createElement("div");
		var ds = div.style;
		ds.position="absolute";
		ds.left="-100px";
		ds.top="0";
		ds.width="30px";
		ds.height="1000em";
		ds.border="0";
		ds.margin="0";
		ds.padding="0";
		ds.outline="0";
		ds.lineHeight="1";
		ds.overflow="hidden";
		dojo.body().appendChild(div);
	
		//	do the measurements.
		for(var p in heights){
			ds.fontSize = p;
			heights[p] = Math.round(div.offsetHeight * 12/16) * 16/12 / 1000;
		}
		
		dojo.body().removeChild(div);
		div = null;
		return heights; 	//	object
	};

	var fontMeasurements = null;
	
	dhm.getCachedFontMeasurements = function(recalculate){
		if(recalculate || !fontMeasurements){
			fontMeasurements = dhm.getFontMeasurements();
		}
		return fontMeasurements;
	};

	var measuringNode = null, empty = {};
	dhm.getTextBox = function(/* String */ text, /* Object */ style, /* String? */ className){
		var m;
		if(!measuringNode){
			m = measuringNode = dojo.doc.createElement("div");
			m.style.position = "absolute";
			m.style.left = "-10000px";
			m.style.top = "0";
			dojo.body().appendChild(m);
		}else{
			m = measuringNode;
		}
		// reset styles
		m.className = "";
		m.style.border = "0";
		m.style.margin = "0";
		m.style.padding = "0";
		m.style.outline = "0";
		// set new style
		if(arguments.length > 1 && style){
			for(var i in style){
				if(i in empty){ continue; }
				m.style[i] = style[i];
			}
		}
		// set classes
		if(arguments.length > 2 && className){
			m.className = className;
		}
		// take a measure
		m.innerHTML = text;
		return dojo.marginBox(m);
	};

	//	determine the scrollbar sizes on load.
	var scroll={ w:16, h:16 };
	dhm.getScrollbar=function(){ return { w:scroll.w, h:scroll.h }; };

	dhm._fontResizeNode = null;

	dhm.initOnFontResize = function(interval){
		var f = dhm._fontResizeNode = dojo.doc.createElement("iframe");
		var fs = f.style;
		fs.position = "absolute";
		fs.width = "5em";
		fs.height = "10em";
		fs.top = "-10000px";
		if(dojo.isIE){
			f.onreadystatechange = function(){
				if(f.contentWindow.document.readyState == "complete"){
					f.onresize = f.contentWindow.parent[dojox._scopeName].html.metrics._fontresize;
				}
			};
		}else{
			f.onload = function(){
				f.contentWindow.onresize = f.contentWindow.parent[dojox._scopeName].html.metrics._fontresize;
			};
		}
		//The script tag is to work around a known firebug race condition.  See comments in bug #9046
		f.setAttribute("src", "javascript:'<html><head><script>if(\"loadFirebugConsole\" in window){window.loadFirebugConsole();}</script></head><body></body></html>'");
		dojo.body().appendChild(f);
		dhm.initOnFontResize = function(){};
	};

	dhm.onFontResize = function(){};
	dhm._fontresize = function(){
		dhm.onFontResize();
	}

	dojo.addOnUnload(function(){
		// destroy our font resize iframe if we have one
		var f = dhm._fontResizeNode;
		if(f){
			if(dojo.isIE && f.onresize){
				f.onresize = null;
			}else if(f.contentWindow && f.contentWindow.onresize){
				f.contentWindow.onresize = null;
			}
			dhm._fontResizeNode = null;
		}
	});

	dojo.addOnLoad(function(){
		// getScrollbar metrics node
		try{
			var n=dojo.doc.createElement("div");
			n.style.cssText = "top:0;left:0;width:100px;height:100px;overflow:scroll;position:absolute;visibility:hidden;";
			dojo.body().appendChild(n);
			scroll.w = n.offsetWidth - n.clientWidth;
			scroll.h = n.offsetHeight - n.clientHeight;
			dojo.body().removeChild(n);
			//console.log("Scroll bar dimensions: ", scroll);
			delete n;
		}catch(e){}

		// text size poll setup
		if("fontSizeWatch" in dojo.config && !!dojo.config.fontSizeWatch){
			dhm.initOnFontResize();
		}
	});
})();
