source: Dev/trunk/src/client/dijit/Viewport.js

define([
        "dojo/Evented",
        "dojo/on",
        "dojo/domReady",
        "dojo/sniff",   // has("ie"), has("ios")
        "dojo/window" // getBox()
], function(Evented, on, domReady, has, winUtils){

        // module:
        //              dijit/Viewport

        /*=====
        return {
                // summary:
                //              Utility singleton to watch for viewport resizes, avoiding duplicate notifications
                //              which can lead to infinite loops.
                // description:
                //              Usage: Viewport.on("resize", myCallback).
                //
                //              myCallback() is called without arguments in case it's _WidgetBase.resize(),
                //              which would interpret the argument as the size to make the widget.
        };
        =====*/

        var Viewport = new Evented();

        var focusedNode;

        domReady(function(){
                var oldBox = winUtils.getBox();
                Viewport._rlh = on(window, "resize", function(){
                        var newBox = winUtils.getBox();
                        if(oldBox.h == newBox.h && oldBox.w == newBox.w){ return; }
                        oldBox = newBox;
                        Viewport.emit("resize");
                });

                // Also catch zoom changes on IE8, since they don't naturally generate resize events
                if(has("ie") == 8){
                        var deviceXDPI = screen.deviceXDPI;
                        setInterval(function(){
                                if(screen.deviceXDPI != deviceXDPI){
                                        deviceXDPI = screen.deviceXDPI;
                                        Viewport.emit("resize");
                                }
                        }, 500);
                }

                // On iOS, keep track of the focused node so we can guess when the keyboard is/isn't being displayed.
                if(has("ios")){
                        on(document, "focusin", function(evt){
                                focusedNode = evt.target;
                        });
                        on(document, "focusout", function(evt){
                                focusedNode = null;
                        });
                }
        });

        Viewport.getEffectiveBox = function(/*Document*/ doc){
                // summary:
                //              Get the size of the viewport, or on mobile devices, the part of the viewport not obscured by the
                //              virtual keyboard.

                var box = winUtils.getBox(doc);

                // Account for iOS virtual keyboard, if it's being shown.  Unfortunately no direct way to check or measure.
                var tag = focusedNode && focusedNode.tagName && focusedNode.tagName.toLowerCase();
                if(has("ios") && focusedNode && !focusedNode.readOnly && (tag == "textarea" || (tag == "input" &&
                        /^(color|email|number|password|search|tel|text|url)$/.test(focusedNode.type)))){

                        // Box represents the size of the viewport.  Some of the viewport is likely covered by the keyboard.
                        // Estimate height of visible viewport assuming viewport goes to bottom of screen, but is covered by keyboard.
                        box.h *= (orientation == 0 || orientation == 180 ? 0.66 : 0.40);

                        // Above measurement will be inaccurate if viewport was scrolled up so far that it ends before the bottom
                        // of the screen.   In this case, keyboard isn't covering as much of the viewport as we thought.
                        // We know the visible size is at least the distance from the top of the viewport to the focused node.
                        var rect = focusedNode.getBoundingClientRect();
                        box.h = Math.max(box.h, rect.top + rect.height);
                }

                return box;
        };

        return Viewport;
});