I have been thinking about how we might develop Flex so that it can target technologies other than the flash player. I have been using JavaScript as my theoretical target because it poses the most problems: we have to convert the AS3 source to another language (not bytecode), we need the output to be as small and fast as possible and - the topic of my thoughts here - we cannot render to the Canvas as it is just too slow, instead components will need to be "rendered" using the DOM and CSS.
My knowledge of skinning Flex 4 components is minimal, but my understanding is that spark components hand off *all* rendering to skin classes. If this is the case, then it might be relatively simple to come up with a multi-target solution. Take a trivially simple app: ------------------------------------- ExampleApp.mxml: <?xml version="1.0" encoding="utf-8"?> <s:Application xmlns:fx="http://ns.adobe.com/mxml/2009"; xmlns:s="library://ns.adobe.com/flex/spark"> <s:Button skinClass="MyButtonSkin"/> </s:Application> ------------------------------------- It references MyButtonSkin class, which might be defined as below: ------------------------------------- MyButtonSkin.mxml (based on example at http://www.adobe.com/devnet/flex/articles/flex4_skinning.html): <?xml version="1.0" encoding="utf-8"?> <s:Skin xmlns:fx="http://ns.adobe.com/mxml/2009"; xmlns:s="library://ns.adobe.com/flex/spark" alpha.disabled=".5" implements="org.apache.flex.compilectrl.INativeClass"> <s:states> ... </s:states> <s:Rect id="rect" radiusX="4" radiusY="4" top="0" right="0" bottom="0" left="0"> ... </s:Rect> <s:Label text="Button" .../> </s:Skin> ------------------------------------- Notice that I have added implements="org.apache.flex.compilectrl.INativeClass." When compiled with, for example --target-javascript, the compiler will disregard the AS3 version of MyButtonSkin, as it is marked as a native class. Instead, the compiler will expect some form of JavaScript, CSS & HTML MyButtonSkin "bundle", which it will link/merge or whatever with the generated JavaScript-based output. The Button class still gets compiled to JavaScript (or .NET bytecode, C++ or whatever we choose to target), but the actual rendering process is handled natively in each case. Would this approach work, or have I missed something important? Obviously having classes implement an interface may not be the most elegant way of handling this and maybe either a new language keyword or metadata could be used instead. Also, this technique would mean that only spark components could be targeted at anything other than the flash player, but I don't see this as a bad thing. Are there any fundamental flaws with the idea though? David.
