January 3, 2004 spout

On Genghis, WinForms and How to Move Towards Avalon

Saturday, January 3rd, 2004

Inspired by my pending interview of Don Box, Paolo Severini sent along an interview for me.

Paul: Being a faithful reader of your books, articles and of your blog, I’d like to ask you a few questions about LH, Avalon and the future of WinForms. Before all, let me say that I’m really fascinated by Longhorn, and especially by Avalon. I installed the PDC stuff as soon as I received it through my MSDN subscription and I’ve begun exploring it with pure geek” enthusiasm. Everything is extremely interesting, but I’m now not sure what to do with it.

Chris: I know what you mean, Paul. I’m going through that myself. Suddenly having so many fewer barriers tends to throw off the engineer in me. I’m working through it by begging the Longhorn User Experience team for guidance, learning Adobe Illustrator, reading graphic design books and trying to open my mind to the graphic designer inside us all (I hope : ).

Paul: Paraphrasing one of the questions you proposed to Don Box: what should a WinForms programmer *really* do today to prepare for Avalon?

Chris: If you want to write code today that’ll work well on Longhorn tomorrow, write WinForms today. WinForms in Whidbey gets tons more features and I expect they’ll be some cool new Longhorn-specific stuff when the time is right. If, when you’re preparing a Longhorn version of your application, you’d like to host Avalon controls from your WinForms app or even build Avalon apps that host your WinForms controls, you’ll be able to do that in Longhorn via WinForms/Avalon interop.

For maximum flexibility in the code you write now, be very thorough about separating the data from the view of the data so that you can write a 100% Avalon front end to replace your WinForms front end if such is your need. Likewise, be very thorough about separating the data from the storage of the data is that you can take advantage of WinFS.

Paul: I’m very grateful to MS for having disclosed their future technologies so soon, and more generally, to have become so opened” to outsider’s eyes, with so many devs and PMs now blogging about their work.

Chris: Me, too. Without this openness, I’d get into lots more trouble. : )

Paul: But I somehow also think that maybe LH was presented a bit too soon. Since it’s not planned to be released before 2006, chances are that the shipped version could be significantly different. (Will it? Is it already? Can you write anything about that? :-).

Chris: I used to think that we were unveiling Longhorn too soon, too. However, the later in the development process we get it out to reviewers, the fewer major changes we’ll be able to make based of your feedback. What that means, of course, is that some major things are going to change between now and release, but those changes will be based on decisions that include feedback from you. The downside is that you’ll have to relearn some of the things you learn with these bits. Hopefully, the upside is that most of what you have to unlearn will be replaced with something significantly better.

Paul: Furthermore, even when the new presentation subsystem will ship, it seems like it won’t be easy to write code that supports both the new and the old platforms, being they so different, and that could slow down its widespread acceptance even more. So I’m afraid that we’ll all have a difficult time writing user interfaces, having to decide whether to take advantage of the new features or simply stay with the old portable libraries. After all, there are today still (too many) people running Windows 9x. And Windows XP is such a great OS that won’t universally be replaced so soon.

Chris: I’ve already mentioned how well WinForms will work under Longhorn, so I think I’ve answered part of your question. However, you’re asking something deeper here, i.e. when do I give up the old way” that has more ubiquitous support for the new way?” In this case, you’re talking about .NET and Longhorn, but you could as easily be talking about DOS and Windows or Win32 and .NET. This is the eternal struggle and the reason that we need software engineers in the first place. As with all such questions, the answer is it depends.”

My general purpose answer is to always pick the newest thing that meets my requirements. The newer the technology you pick, the longer the shelf life. Can I build cool, scalable apps that take advantage of the high resolution monitors and GPUs of tomorrow in DOS? Absolutely. Do I want to? Hell no. Can I do it in WinForms? Yes, although it’ll still be harder than doing it on Avalon. Will I increase my available market by targeting DOS today? The answer used to be yes,” but for a while now it’s been no.” What about WinForms? The answer is definitely yes” today and will be for a while yet, even after Longhorn ships.

The answer to the question of when to adopt new technology has too many variables for me to provide any general advice better than as soon as possible.” Of course, Microsoft wants the answer to that question to be sooner rather than later,” and we’re working to make Longhorn kick-ass for developers, business users and consumers so that ubiquity is taken out of the equation as soon as possible. Please use all channels of communication you have into the company to help us make sure we’re doing that. The WinFX newsgroups are one good place for such feedback. They are heavily monitored by all of the WinFX teams and the Longhorn User Experience (Aero) Team.

Paul: I found out that the PDC build of Avalon doesn’t really work in kernel mode but simply uses two (unmanaged) DLLs, milcore and milrender built upon the old GDI APIs (to the point that it is actually possible to run Avalon on XP). Of course, that’s bound to change, as Chris Anderson wrote, with the new video driver model and when the desktop composition stuff will get turned on. But wouldn’t it be nice if a subset of Avalon ran on XP? After all, not every app will take advantage of its more advanced features.

Chris: Before I answer this question, I just wanted to point out that GDI is not part of the Avalon rendering path. Instead, Avalon is built on DirectX, which is built directly on the drivers. GDI is still supported, of course, but it’s a parallel rending path to Avalon’s.

The answer to the core question, i.e. why not ship Avalon on XP, is one of resources. Chris Anderson once told me that something like a man millennia has gone into the development of Avalon thus far. Even if Chris was exaggerating for effect, that’s still one hell of a lot of work. That work has gone into building an architecture that allows application developers to take advantage of features present all the way down to the hardware level, including changes at every point in the presentation stack. What kind of work do you think it would take to make a subset of that available under Windows XP? Or Windows 2000? Or Windows 98? What kind of work do you think it would take to support those features on those down-level operating systems in their subsetted states? If we’re looking at a release years into the future already, how many more years are we willing to wait to release Avalon in a form that works in a subsetted form on those OSes? And what will we ship to our customers expected a new OS in the meantime?

It may be that you could come up with answers that you love to these questions. Would our other customers answer them the same way? Would our shareholders answer them the same way? Would your answers best position us against our competitors?

Even if you got a subset of Avalon that works across .NET platforms today, would it really enable you to be more successful at your business or is it an engineering gosh that’d be neat?”

I know that our product teams really listen to our customers these days, so if you’ve got specific scenarios that you need enabled to be successful, please let them know.

Paul: Furthermore, if XAML is, in the end, only a way to glue together a graph of CLR objects, why don’t use it also to build WinForms UI? Both these options would make the transition much easier.

Now that’s a question I can provide a more satisfactory answer to, I think (sorry about that last answer : ). In the Longhorn PDC bits today, you can generate WinForms apps using XAML for the very reason you state. Likewise, if you’d like to try a subset of XAML in today’s version of the .NET Framework, there are not one, but two 3rd parties providing early access to projects to allow this to happen. Given the amount of work that has gone into, and will go into, getting Avalon out the door, I doubt very much that their versions of XAML will be full-featured, but it may help ease the transition, as you say.

Paul: That brings me to ask you about the future of WinForms (about which I’m now reading your book and really enjoying it). In the near future I will surely have to write WinForms code. But is it still worthwhile to spend time studying and trying to improve it? (I personally think so). Or should I rather concentrate my interest learning everything about the new LH technologies? So I’m back on the question about how to prepare for Avalon…

Chris: I’d say that it absolutely makes sense to continue to write WinForms applications for years to come. Not only in WinForms a great platform for client applications today, but in Whidbey, it about doubles in size and capability. Plus, WinForms applications will continue to work great under Longhorn and will form the core of an application that needs to take advantage of Longhorn features under Longhorn but continue to work on the rest of the .NET platform. Unless you are planning to target only Longhorn, WinForms is absolutely where you should be spending your client development effort today and for years to come.

Paul: Speaking of WinForms, one of the things I’ve never liked is the absence of windowless controls. It has been said that windowed and windowless controls are difficult to make live together, and that’s true. But windowless controls are sometimes very useful (and cool! just think to the Windows Media Player UI). I found in your Genghis page that the Windowless control architecture” feature is still opened” and I’d like to try to work on it. (In the past, I wrote an ActiveX control container that supported windowless controls, so I wouldn’t start from zero).

Chris: Windowless controls were meant mostly as an optimization when creating thousands of Window handles brought the platform to its knees. Some folks also used windowless controls as a good way to fake non-rectangular controls. In modern implementations of User32, neither is much of an issue, so windowless controls provide a service that is no longer required in most cases. In the specialized cases where it is still necessary, I find that building an aggregate control that does the drawing of multiple controls that you would have made windowless in the past solves most of my needs in this area, although your mileage may vary. Given that Genghis has most of the rest of the features that I wanted for it, but no windowless control architecture, I’d say that folks seem to agree with me that windowless controls are no longer as important as they once were.

Paul: But I also noticed that the Genghis project has been still for a few months, so I’m now wondering if it is still alive and if my project still makes sense now that Avalon is on its way. May you give me an advice?

Chris: I was waiting for a wizard that would generate MDI, SDI and multi-SDI applications before shipping the next drop of Genghis, but there are enough new things and fixes that we should have another version of Genghis out in a week or so. If you or anyone would like to build the wizard (or just send Scott Densmore email begging him to finish the one he already started and has promised to me several times) that’d be great.

Thanks for your wonderful job and for the time you dedicated to this mail. I just hope my English was understandable… :-)

Best regards from Italy,
Have a wonderful new year!
–Paolo Severini