[Peek] Terminate Preview Handlers Processes (#40116)

<!-- 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 🤔

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## 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

src/modules/peek/Peek.FilePreviewer/Previewers/ShellPreviewHandlerPreviewer/ShellPreviewHandlerPreviewer.cs

@@ -90,14 +90,12 @@ namespace Peek.FilePreviewer.Previewers
                         unsafe
                         {
                             // This runs the preview handler in a separate process (prevhost.exe)
-                            // TODO: Figure out how to get it to run in a low integrity level
                             if (!HandlerFactories.TryGetValue(clsid, out var factory))
                             {
                                 var hr = PInvoke_FilePreviewer.CoGetClassObject(clsid, CLSCTX.CLSCTX_LOCAL_SERVER, null, typeof(IClassFactory).GUID, out object pFactory);
                                 Marshal.ThrowExceptionForHR(hr);
 
                                 // Storing the factory in memory helps makes the handlers load faster
-                                // TODO: Maybe free them after some inactivity or when Peek quits?
                                 factory = (IClassFactory)pFactory;
                                 factory.LockServer(true);
                                 HandlerFactories.AddOrUpdate(clsid, factory, (_, _) => factory);
@@ -213,6 +211,20 @@ namespace Peek.FilePreviewer.Previewers
             return !string.IsNullOrEmpty(GetPreviewHandlerGuid(item.Extension));
         }
 
+        public static void ReleaseHandlerFactories()
+        {
+            foreach (var factory in HandlerFactories.Values)
+            {
+                try
+                {
+                    Marshal.FinalReleaseComObject(factory);
+                }
+                catch
+                {
+                }
+            }
+        }
+
         private static string? GetPreviewHandlerGuid(string fileExt)
         {
             const string PreviewHandlerKeyPath = "shellex\\{8895b1c6-b41f-4c1c-a562-0d564250836f}";

src/modules/peek/Peek.UI/PeekXAML/App.xaml.cs

@@ -12,6 +12,7 @@ using Microsoft.UI.Xaml;
 using Peek.Common;
 using Peek.FilePreviewer;
 using Peek.FilePreviewer.Models;
+using Peek.FilePreviewer.Previewers;
 using Peek.UI.Native;
 using Peek.UI.Telemetry.Events;
 using Peek.UI.Views;
@@ -111,6 +112,7 @@ namespace Peek.UI
             NativeEventWaiter.WaitForEventLoop(Constants.ShowPeekEvent(), OnPeekHotkey);
             NativeEventWaiter.WaitForEventLoop(Constants.TerminatePeekEvent(), () =>
             {
+                ShellPreviewHandlerPreviewer.ReleaseHandlerFactories();
                 EtwTrace?.Dispose();
                 Environment.Exit(0);
             });

src/modules/peek/Peek.UI/PeekXAML/MainWindow.xaml.cs

@@ -15,6 +15,7 @@ using Microsoft.UI.Xaml.Input;
 using Peek.Common.Constants;
 using Peek.Common.Extensions;
 using Peek.FilePreviewer.Models;
+using Peek.FilePreviewer.Previewers;
 using Peek.UI.Extensions;
 using Peek.UI.Helpers;
 using Peek.UI.Telemetry.Events;
@@ -204,6 +205,8 @@ namespace Peek.UI
             ViewModel.ScalingFactor = 1;
 
             this.Content.KeyUp -= Content_KeyUp;
+
+            ShellPreviewHandlerPreviewer.ReleaseHandlerFactories();
         }
 
         /// <summary>

src/modules/peek/peek/dllmain.cpp

@@ -405,13 +405,19 @@ public:
         {
             ResetEvent(m_hInvokeEvent);
             SetEvent(m_hTerminateEvent);
-            WaitForSingleObject(m_hProcess, 1500);
-            auto result = TerminateProcess(m_hProcess, 1);
-            if (result == 0)
+
+            HANDLE hProcess = OpenProcess(SYNCHRONIZE | PROCESS_TERMINATE, FALSE, m_processPid);
+            if (WaitForSingleObject(hProcess, 1500) == WAIT_TIMEOUT)
             {
-                int error = GetLastError();
-                Logger::trace("Couldn't terminate the process. Last error: {}", error);
+                auto result = TerminateProcess(hProcess, 1);
+                if (result == 0)
+                {
+                    int error = GetLastError();
+                    Logger::trace("Couldn't terminate the process. Last error: {}", error);
+                }
             }
+
+            CloseHandle(hProcess);
             CloseHandle(m_hProcess);
             m_hProcess = 0;
             m_processPid = 0;