source: Dev/trunk/src/client/dojox/html/metrics.js

define(["dojo/_base/kernel","dojo/_base/lang", "dojo/_base/sniff", "dojo/ready", "dojo/_base/unload",
                "dojo/_base/window", "dojo/dom-geometry"],
  function(kernel,lang,has,ready,UnloadUtil,Window,DOMGeom){
        var dhm = lang.getObject("dojox.html.metrics",true);
        var dojox = lang.getObject("dojox");

        //      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(has("ie")){
                        //      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.
                        Window.doc.documentElement.style.fontSize="100%";
                }
        
                //      set up the measuring node.
                var div=Window.doc.createElement("div");
                var ds = div.style;
                ds.position="absolute";
                ds.left="-100px";
                ds.top="0";
                ds.width="30px";
                ds.height="1000em";
                ds.borderWidth="0";
                ds.margin="0";
                ds.padding="0";
                ds.outline="0";
                ds.lineHeight="1";
                ds.overflow="hidden";
                Window.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;
                }
                
                Window.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, s;
                if(!measuringNode){
                        m = measuringNode = Window.doc.createElement("div");
                        // Container that we can set contraints on so that it doesn't
                        // trigger a scrollbar.
                        var c = Window.doc.createElement("div");
                        c.appendChild(m);
                        s = c.style;
                        s.overflow='scroll';
                        s.position = "absolute";
                        s.left = "0px";
                        s.top = "-10000px";
                        s.width = "1px";
                        s.height = "1px";
                        s.visibility = "hidden";
                        s.borderWidth = "0";
                        s.margin = "0";
                        s.padding = "0";
                        s.outline = "0";
                        Window.body().appendChild(c);
                }else{
                        m = measuringNode;
                }
                // reset styles
                m.className = "";
                s = m.style;
                s.borderWidth = "0";
                s.margin = "0";
                s.padding = "0";
                s.outline = "0";
                // set new style
                if(arguments.length > 1 && style){
                        for(var i in style){
                                if(i in empty){ continue; }
                                s[i] = style[i];
                        }
                }
                // set classes
                if(arguments.length > 2 && className){
                        m.className = className;
                }
                // take a measure
                m.innerHTML = text;
                var box = DOMGeom.position(m);
                // position doesn't report right (reports 1, since parent is 1)
                // So we have to look at the scrollWidth to get the real width
                // Height is right.
                box.w = m.parentNode.scrollWidth;
                return box;
        };

        //      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 = Window.doc.createElement("iframe");
                var fs = f.style;
                fs.position = "absolute";
                fs.width = "5em";
                fs.height = "10em";
                fs.top = "-10000px";
                fs.display = "none";
                if(has("ie")){
                        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>'");
                Window.body().appendChild(f);
                dhm.initOnFontResize = function(){};
        };

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

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

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

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