On Nov 21, 2014, at 7:25 PM, MarLOne <infoseeker...@gmail.com> wrote:
> It will be good if these classes and assemblies from Microsoft open-sources
> are incorporated verbatim into Mono to replace its inconsistent code.
This will not be possible, for (at least) three reasons:
1. That code is also shared by Xamarin.Android, Xamarin.iOS, and Xamarin.Mac,
all of which lack System.Configuration.dll, and the .NET DefaultTraceListener
relies upon System.Configuration (via DiagnosticsConfiguration).
2. There are several CAS demands, which don't make sense on Mono.
3. The default code to write messages is useless outside of Windows, as no
other platform has OutputDebugString():
https://github.com/Microsoft/referencesource/blob/9da503f9ef21e8d1f2905c78d4e3e5cbb3d6f85a/System/compmod/system/diagnostics/DefaultTraceListener.cs#L182-191
This doesn't mean that the .NET source can't be taken *and modified* for use
off Windows, but it can't be used as-is.
> I have to thank Microsoft to open-source the .Net library allowing me to read
> ... default values for the System.Diagnostics.DefaultTraceListener.
> The default value of property that determines the reaction of Debug.Assert is
> set here: assertuienabled
The hilarious thing is that AssertUiEnabled does not alone control actual
runtime behavior!
https://github.com/Microsoft/referencesource/blob/9da503f9ef21e8d1f2905c78d4e3e5cbb3d6f85a/System/compmod/system/diagnostics/DefaultTraceListener.cs#L105-107
The behavior of DefaultTraceListener.Fail() depends on *both*
DefaultTraceListener.AssertUiEnabled *and* DefaultTraceListener.UiPermission,
which is a private property that demands the UIPermissionWindow.SafeSubWindows
CAS permission:
try {
new
UIPermission(UIPermissionWindow.SafeSubWindows).Demand();
return true;
}
catch {
return false;
}
This explains how they can sanely have a non-GUI Windows service use
Debug.Assert() and have it not hang when there's no Window Station: just have
the startup code set security permissions which denies
UIPermissionWindow.SafeSubWindows...
This doesn't at all answer how things should work off Windows. You can
reasonably argue that DefaultTraceListener.AssertUiEnabled should default to
`true` off Windows, even if/when a GUI is never shown, because
DefaultTraceListener.AssertUiEnabled is in fact meaningless (it's not the sole
control over whether a GUI is shown).
Which really means the docs are misleading. :-)
http://msdn.microsoft.com/en-us/library/system.diagnostics.defaulttracelistener.assertuienabled(v=vs.110).aspx
It's entirely possible, as we can now see, for "user interface mode" to be
enabled, yet still not actually display a GUI when Fail() is invoked. This
possibility is not noted at all in the documentation, afaict.
- Jon
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