fix #923

[remcoros]

No description provided.

[AzureKitsune]

There was a reason for that code being there. I just can't remember why.

cc @punker76

[remcoros]

I did a little bit of research.

If you look at the source of SystemResources.cs in .Net (http://www.dotnetframework.org/default.aspx/Dotnetfx_Win7_3@5@1/Dotnetfx_Win7_3@5@1/3@5@1/DEVDIV/depot/DevDiv/releases/Orcas/NetFXw7/wpf/src/Framework/System/Windows/SystemResources@cs/5/SystemResources@cs)

Line 1056 ( case NativeMethods.WM_THEMECHANGED:)

the order of invalidation is
SystemColors.InvalidateCache();
SystemParameters.InvalidateCache();
OnThemeChanged();
InvalidateResources(false)

The same as the work-around in ThemeManager.

The reason is probably (as stated in the comments), that system colors weren't changing and need to be invalidated.

BUT, As you can read on that SO question (and issue #923) this causes some issues with Measurement / weird double click behavior and something with MediaElement (I don't know what though).

Trough trial and error, I found out that if we leave everything as is, except for SystemParameters.InvalidateCache(). The colors are changing and the weird measure/click behavior is fixed.

From what I can see in my own app, everything seems to work now and no weird behavior is observed.

edit: Also, from what I can read 'SystemParameters' has mostly todo with sizes (height/width etc). (http://msdn.microsoft.com/en-us/library/system.windows.systemparameters(v=vs.110).aspx)

As ThemeManager is about colors and not sizing, I think it is safe to skip this call.

[punker76]

the demo works, so we can merge this