Zoom scroller "to fit"?

Question

I have a group component in a scroller.  My application will add children to this component.  The component's scale is set with a Spark HSlider.  Fine.
However, I'd like to provide a "zoom to fit" button.  I can get the size in pixels of all the children added, no problem. My question is how I can use this dimension to properly set the scaleX and scaleY so it fits in the viewport.
<s:Group id="clipWindow" width="720" height="480">
     <s:Scroller id="imgScroll" top="0" left="0" bottom="0" right="0">
          <s:Group id="bgimg" scaleX="{scaleSlider.value}" scaleY="{scaleSlider.value}">
               <com:WorkshopStage id="ws" />
          </s:Group>
     </s:Scroller>
</s:Group>

Answer 1

Basicly this is only math stuff. Here is what you will have to write inside your "Zoom To Fit" handler:
bgimg.scaleX = bgimg.scaleY = Math.min(clipWindow.width  / ws.width,
                                       clipWindow.height / ws.height,
                                       1);
Now this formula only scales down your bgimg if it (actually I use dimensions of ws but that does not matter here) is larger than the clipWindow. If it is smaller, scale will be 1: it won't scale up.
And as you can see there is no need for calculating the size of ws manually by somehow checking all children: flex does that for you when components are measured.
Michael