<!-- Enter a brief description/summary of your PR here. What does it
fix/what does it change/how was it tested (even manually, if necessary)?
-->
## Summary of the Pull Request
This is an attempt to release Preview Handlers instantiated by Peek and
close the related processe.
⚠️ Note that even if the PR improve the current behavior, the solution
doesn't work 100% of times.
I noticed that sometimes the process gets leaked also when Preview
Handler is used in Explorer 🤔
<!-- Please review the items on the PR checklist before submitting-->
## PR Checklist
- [x] **Closes:** #40117
- [ ] **Communication:** I've discussed this with core contributors
already. If the work hasn't been agreed, this work might be rejected
- [ ] **Tests:** Added/updated and all pass
- [ ] **Localization:** All end-user-facing strings can be localized
- [ ] **Dev docs:** Added/updated
- [ ] **New binaries:** Added on the required places
- [ ] [JSON for
signing](https://github.com/microsoft/PowerToys/blob/main/.pipelines/ESRPSigning_core.json)
for new binaries
- [ ] [WXS for
installer](https://github.com/microsoft/PowerToys/blob/main/installer/PowerToysSetup/Product.wxs)
for new binaries and localization folder
- [ ] [YML for CI
pipeline](https://github.com/microsoft/PowerToys/blob/main/.pipelines/ci/templates/build-powertoys-steps.yml)
for new test projects
- [ ] [YML for signed
pipeline](https://github.com/microsoft/PowerToys/blob/main/.pipelines/release.yml)
- [ ] **Documentation updated:** If checked, please file a pull request
on [our docs
repo](https://github.com/MicrosoftDocs/windows-uwp/tree/docs/hub/powertoys)
and link it here: #xxx
<!-- Provide a more detailed description of the PR, other things fixed,
or any additional comments/features here -->
## Detailed Description of the Pull Request / Additional comments
- Ported the same fix applied to CmdPal to ensure the process is
terminated gracefully instead of being killed:
https://github.com/microsoft/PowerToys/pull/39589
- Attempt to cleanup Preview Handlers and close the relative process
<!-- Describe how you validated the behavior. Add automated tests
wherever possible, but list manual validation steps taken as well -->
## Validation Steps Performed
Tested manually:
- Preview through some Excel and Word files
- Close Peek window
- Excel and Word processes are closed
<!-- Enter a brief description/summary of your PR here. What does it
fix/what does it change/how was it tested (even manually, if necessary)?
-->
## Summary of the Pull Request
CsWin32 0.3.183 broke preview through preview handlers in Peek.
`Error in UpdatePreviewAsync, falling back to default previewer: Unable
to cast COM object of type 'System.__ComObject' to class type
'System.IntPtr'. Instances of types that represent COM components cannot
be cast to types that do not represent COM components; however they can
be cast to interfaces as long as the underlying COM component supports
QueryInterface calls for the IID of the interface.`
Signature of `CoGetClassObject` changed for last argument from `void*`
to `object`.
Thanks @AArnott 🙂
<!-- Please review the items on the PR checklist before submitting-->
## PR Checklist
- [ ] **Closes:** #xxx
- [ ] **Communication:** I've discussed this with core contributors
already. If the work hasn't been agreed, this work might be rejected
- [ ] **Tests:** Added/updated and all pass
- [ ] **Localization:** All end-user-facing strings can be localized
- [ ] **Dev docs:** Added/updated
- [ ] **New binaries:** Added on the required places
- [ ] [JSON for
signing](https://github.com/microsoft/PowerToys/blob/main/.pipelines/ESRPSigning_core.json)
for new binaries
- [ ] [WXS for
installer](https://github.com/microsoft/PowerToys/blob/main/installer/PowerToysSetup/Product.wxs)
for new binaries and localization folder
- [ ] [YML for CI
pipeline](https://github.com/microsoft/PowerToys/blob/main/.pipelines/ci/templates/build-powertoys-steps.yml)
for new test projects
- [ ] [YML for signed
pipeline](https://github.com/microsoft/PowerToys/blob/main/.pipelines/release.yml)
- [ ] **Documentation updated:** If checked, please file a pull request
on [our docs
repo](https://github.com/MicrosoftDocs/windows-uwp/tree/docs/hub/powertoys)
and link it here: #xxx
<!-- Provide a more detailed description of the PR, other things fixed,
or any additional comments/features here -->
## Detailed Description of the Pull Request / Additional comments
<!-- Describe how you validated the behavior. Add automated tests
wherever possible, but list manual validation steps taken as well -->
## Validation Steps Performed
Tested Preview of Office files in Peek.
* Add support for preview handlers
* Fix spelling
* Fix DPI resizing and redraw
* Make source into an ObservableProperty
* Add handler visibility property
* Better error handling
* Add support for IInitializeWithItem
* Run preview handlers in separate processes
* Fix redrawing when switching previewers
