The All-Avalon, All-the-time Application

Expression Interactive Designer (aka Sparkle) is a 100% .NET, managed
code application.  The source is currently more than 1200 .cs
files and about 140 .xaml files totally 210,000 some lines of C# and
23,000 some lines of XAML.  There is no unmanaged code directly in
the Sparkle source, and only one PInvoke.  The single PInvoke is
used to call out to HtmlHelp.  We could have used the managed
wrapper for HtmlHelp, but that is in the WinForms assemblies, and since
we are so Avalon based we decided to avoid additional WinForms
dependencies (frankly, for interop reasons we will probably have them
anyway, but sometimes it is the thought that counts).

As I mentioned in my attempt at Sparkle history, we decided early on to
build Sparkle's UI using Avalon even though Avalon was very rough and
untested at the time.  We almost certainly could have made faster
progress using a fully functional and tested UI framework like WinForms
or even using unmanaged Win32.  We certainly would have avoided a
huge amount of churn as we constantly fixed or rewrote our code when
Avalon changed. 

I recently heard that in some early review BillG said Sparkle should
"be the conscience of Avalon."  I wish I had heard it then,
because it is a great summary of how we felt.  As much as we were
all committed to making our team's product succeed, we always knew
Avalon was more important.  We needed to look at Avalon the way
the customer would when they started building their applications. 
Frankly, there is no artifical test or team of QA people that can match
trying to build real, production code on a platform.  We tried to
do everything the Avalon way, and tried to use Avalon features we
weren't even sure we needed.  At some point somebody starting
calling us "The All-Avalon, All-the-time application". 

We don't cover every area of Avalon, but we hit most of them and
provided a lot of feedback to the Avalon team.  Which was
hard...because the Avalon folks were working very, very hard and most
of the time all they heard about from us were the bugs and the missing

And the gamble paid off.  Sparkle works and has a very powerful,
unique UI.  Because we are all-managed and all-Avalon we don't
have a lot of fiddly interop code.  And we have some features
(like the zooming UI) that would have been much harder to build on
another platform, if even possible.

Comments (4)
  1. jmacdonagh says:

    I understand the need for the HtmlHelp call, and I understand the desire to utilize Microsoft’s HTML Help framework, but why not replace all those ugly help files with a flashy help file using Avalon’s document features? Either that, or talk to the WinFX team about putting in a managed wrapper around it.

  2. JohnGossman says:

    The tools and infrastructure for a replacement for HTML help will take time to build. I think the WinFX team is ambivalent about adding another wrapper (since one already exists in WinForms) when we don’t know whether HTMLHelp is the right long term strategy.

  3. Microsoft has used Avalon internally already for a major application: Sparkle. Expression Interactive

  4. In case anyone ever wonders if Microsoft produces any real apps (other than Microsoft Max ) using managed code, here you go: Expression Interactive Designer (aka Sparkle) is a 100% .NET, managed code application. The source is currently more than 1200

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