Fix wrong thread issue when scrolling with the middle mouse button from a se…

[Polf]

…condary window

Fixes

Fixes the "COM object that has been separated from its underlying RCW" issue that causes the application to crash when scrolling with the middle mouse button from a secondary window

PR Type

What kind of change does this PR introduce?

• Bugfix

What is the current behavior?

Steps to reproduce
When an application can open a secondary window, and this secondary window contains a ScrollViewer with EnableMiddleClickScrolling enabled:

1. Start the application
2. Open a secondary window
3. Scroll inside the ScrollViewer with the middle mouse button
   This causes an unhandled exception in the application, with the message "COM object that has been separated from its underlying RCW".

What is the new behavior?

The exception disappears and the user can scroll with the middle mouse button from a secondary window.

PR Checklist

Please check if your PR fulfills the following requirements:

• Tested code with current supported SDKs
• Pull Request has been submitted to the documentation repository instructions. Link:
• Sample in sample app has been added / updated (for bug fixes / features)
  • Icon has been created (if new sample) following the Thumbnail Style Guide and templates
• Tests for the changes have been added (for bug fixes / features) (if applicable)
• Header has been added to all new source files (run build/UpdateHeaders.bat)
• Contains NO breaking changes

Other information

[ghost]

Thanks Polf for opening a Pull Request! The reviewers will test the PR and highlight if there is any conflict or changes required. If the PR is approved we will proceed to merge the pull request 🙌

[michael-hawker]

@azchohfi I think this is fine for now, this should be resolved in 7.0.0 already through the switch you made for Dispatcher Queue, eh? Did you want to double-check that quick and then we'll just merge this as a temp-fix?

[azchohfi]

Are we shipping a 6.1.1? If not, then I think this fix is not required. 7.0 will directly conflict with this. I'm ok merging it thou, as it is a better solution than the current one.