FAQ: How can I make my Flash Catalyst application scale/use a liquid layout?
Flash Catalyst CS5 currently only supports applications with fixed dimensions. Custom components you create in Catalyst have absolute sizing.
If you want to experiment with creating resizable applications (liquid layouts) and components in a preview of the next version of Flash Catalyst, codenamed "Panini", you can find more information here:
Introducing Adobe Flash Catalyst "Panini"
Download Adobe Flash Catalyst "Panini"
Adobe Flash Catalyst "Panini" help
Keep in mind that Flash Catalyst "Panini" preview is meant for exploration and testing, not real production. If you are doing real production work, here are some options that work with Flash Catalyst CS5 and Flash Builder:
Liquid Layouts
If you are building an application that requires relative constraints, you can take the FXP file from Flash Catalyst into Flash Builder, and apply constraints there so that your components resize according to your application dimensions.
For more info, see this Help topic:
Using constraint-based layouts in Flash Builder
SWF Scaling
If you want your swf to scale, without relative constraints, there's a simple way to make that work in Builder as well. Simply save out your FXP file from Flash Catalyst and import it into Flash Builder. Open up the "Main.mxml" file. Remove the width and height attributes on the Application tag, and add the attribute:
preinitialize="systemManager.stage.scaleMode='showAll'
The entire Application tag should look something like:
<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009"
xmlns:s="library://ns.adobe.com/flex/spark"
xmlns:d="http://ns.adobe.com/fxg/2008/dt"
xmlns:fc="http://ns.adobe.com/flashcatalyst/2009"
xmlns:ATE="http://ns.adobe.com/ate/2009"
xmlns:ai="http://ns.adobe.com/ai/2009"
xmlns:flm="http://ns.adobe.com/flame/2008"
xmlns:lib="assets.graphics.*"
xmlns:components="components.*"
backgroundColor="#FFFFFF"
preloaderChromeColor="#FFFFFF"
preinitialize="systemManager.stage.scaleMode='showAll'"
>
There are a couple other scale modes you may want to try, such as "exactFit", which are outlined at the below link:
Finally, you will have to adjust the object embed code in your html page to set the size of your swf.
Original discussion here