DispatcherHelper constructor throws expected exception, creates developer confusion #1434
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jevansaks
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Oct 10, 2019
jevansaks
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oldnewthing
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May 22, 2020
Improvement to microsoft#1434 by switching from CoreApplicationView::GetForCurrentThread to CoreWindow::GetForCurrentThread. The difference is that CoreApplicationView::GetForCurrentThread throws if not called on a UI thread, whereas CoreWindow::GetForCurrentThread just returns null. The CoreWindow and CoreApplicationView have the same dispatcher, and switching to CoreWindow removes the need to work around the CoreApplicationView behavior.
ranjeshj
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May 27, 2020
Improvement to #1434 by switching from CoreApplicationView::GetForCurrentThread to CoreWindow::GetForCurrentThread. The difference is that CoreApplicationView::GetForCurrentThread throws if not called on a UI thread, whereas CoreWindow::GetForCurrentThread just returns null. The CoreWindow and CoreApplicationView have the same dispatcher, and switching to CoreWindow removes the need to work around the CoreApplicationView behavior.
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DispatcherHelper calls winrt::CoreApplication::GetCurrentView, and catches any exceptions that are thrown. This gives the functionally desired behavior, but it results in debugger exception noise. To avoid using exceptions as control flow, we avoid calling the cppwinrt api here and instead call directly into the abi.
See #1414
We also want this change to go into the OS. I will port the change there once this PR has been merged.