Adobe AIR Sample Application to display a popup window on multiple monitors

ScreenDemo.mxml:

<?xml version="1.0" encoding="utf-8"?>
<mx:WindowedApplication xmlns:mx="http://www.adobe.com/2006/mxml" layout="vertical" 
    height="100%" width="100%" backgroundColor="#323232" creationComplete="init()" remove="removePopups();">
    <mx:Script>
        <![CDATA[
        import mx.controls.Button;
        import flash.display.Screen;
        import mx.controls.Alert;
        private var winNumber:int = 0;
        private var myWindows:Array = new Array();
        
        private function init():void {
            var mainScreen:Screen = Screen.mainScreen; // Main screen as defined by OS (see docs)
            var screenArray:Array = Screen.screens;
            message.text = "Screens found:\n";
            var virtualBounds:Rectangle = new Rectangle();

            for each(var screen:Screen in screenArray) {
                message.text += "\tScreen Size: " + screen.bounds.width + "x" + screen.bounds.height + "\n";
                message.text += "\tVisible Bounds (excludes taskbar/menubar/dock):" + screen.visibleBounds.width + "x" + screen.visibleBounds.height + "\n";
                message.text += "\tColors: " + screen.colorDepth.toString() + " bit\n\n";
                
                // Calculate virtual screen size (combines monitor resolutions)
                if(virtualBounds.left   > screen.bounds.left)   {virtualBounds.left = screen.bounds.left;}
                if(virtualBounds.right  < screen.bounds.right)  {virtualBounds.right = screen.bounds.right;}
                if(virtualBounds.top    > screen.bounds.top)    {virtualBounds.top = screen.bounds.top;}
                if(virtualBounds.bottom < screen.bounds.bottom) {virtualBounds.bottom = screen.bounds.bottom;}
                
                // Determine the center point of each screen
                var centerX:int = screen.bounds.right  - screen.bounds.width  + (screen.bounds.width  / 2);
                var centerY:int = screen.bounds.bottom - screen.bounds.height + (screen.bounds.height / 2);

                // Open a window in the center of each screen
                myWindows[winNumber] = new DemoWindow();
                myWindows[winNumber].open();
                myWindows[winNumber].setMsg("Screen Size: " + screen.bounds.width + "x" + screen.bounds.height + " (" + screen.colorDepth.toString() + " bit)");
                myWindows[winNumber].move(centerX - (myWindows[winNumber].width)/2, centerY - (myWindows[winNumber].height)/2);
                ++winNumber;
            }
            message.text += "Virtual Screen Size: " + virtualBounds.width + "x" + virtualBounds.height + "\n";
        }
        

        private function removePopups():void {
            var i:int;
            for (i = 0; i<winNumber; ++i) myWindows[i].close();
        }
        ]]>
    </mx:Script>
    <mx:TextArea id="message" borderThickness="0" color="white" backgroundColor="#323232" width="100%" height="100%"/>

</mx:WindowedApplication>

DemoWindow.mxml (the popup itself):

<?xml version="1.0" encoding="utf-8"?>
<mx:Window xmlns:mx="http://www.adobe.com/2006/mxml" layout="vertical" verticalAlign="middle" 
    horizontalAlign="center" backgroundColor="#3333FF" width="250" height="90" 
    showStatusBar="false" showTitleBar="false" showGripper="false" borderStyle="none">
    
<mx:Script>
    <![CDATA[
        public function setMsg(msgIn:String):void {
            msg.text = msgIn;
        }
    ]]>
</mx:Script>
    <mx:Label id="msg" fontWeight="bold" color="white" />
    <mx:Button id="winButton" label="Close" click="this.close()"/>
</mx:Window>

This sample is also available in Tour de Flex