[Registry Preview] Adds application to Open with list for REG files (#26033)

* 25834

* Asociate Registry Preview with .reg files

* Add setting for making RP default app for .reg files

* Run spellcheck

* Run spellcheck again

* Fix build

---------

Co-authored-by: Stefan Markovic <stefan@janeasystems.com>

.github/actions/spell-check/expect.txt

@@ -91,7 +91,6 @@ APPIDS
 appium
 Applets
 Applicationcan
-applicationconfiguration
 applicationframehost
 appmanifest
 APPNAME
@@ -158,7 +157,6 @@ BCB
 BCCE
 BCCEA
 bck
-Bcl
 BDB
 BDBAD
 BDCC
@@ -239,7 +237,6 @@ Cangjie
 CANRENAME
 CAPTUREBLT
 CAPTURECHANGED
-CARRAY
 CAtl
 CBA
 CBB
@@ -281,7 +278,6 @@ chdir
 CHILDACTIVATE
 CHILDWINDOW
 chrdavis
-Chromakey
 Chrzan
 CHT
 cidl
@@ -424,7 +420,6 @@ Dac
 dacl
 DAF
 damienleroy
-DANGEROUSLYCOMMITMERELYTODISKCACHE
 DARKPURPLE
 DARKTEAL
 DARKYELLOW
@@ -456,13 +451,11 @@ dcompi
 DComposition
 dcr
 dcs
-Dct
 DDCDD
 DDCE
 DDEIf
 DDevice
 ddf
-Dds
 DDxgi
 Deact
 debian
@@ -494,8 +487,6 @@ depersist
 deprioritized
 depsfileslistspath
 deref
-READOBJECTS
-WRITEOBJECTS
 DESKTOPABSOLUTEEDITING
 DESKTOPABSOLUTEPARSING
 desktopshorcutinstalled
@@ -623,6 +614,7 @@ Emoji
 ENABLEDELAYEDEXPANSION
 enabledisable
 ENABLEDPOPUP
+encodedlaunch
 encryptor
 endpointvolume
 endregion
@@ -663,8 +655,6 @@ exabyte
 examplehandler
 examplepowertoy
 EXAND
-Excep
-EXCEPINFO
 EXCLUDEFROMCAPTURE
 exdisp
 executionpolicy
@@ -789,7 +779,6 @@ GETSTATE
 GETTEXT
 GETTEXTLENGTH
 GHND
-Globbing
 GMEM
 GNumber
 google
@@ -834,7 +823,6 @@ HCRYPTHASH
 HCRYPTPROV
 hcwhite
 hdc
-HDR
 hdrop
 hdwwiz
 HEB
@@ -916,17 +904,12 @@ HWNDPREV
 hyjiacan
 IBase
 IBeam
-IBitmap
-IBlock
 ICapture
 ICEBLUE
 IClass
-IColor
 ICONERROR
-IContext
 IData
 IDD
-IDecoder
 IDesktop
 IDirect
 idl
@@ -935,7 +918,6 @@ IDOn
 IDR
 idx
 IDXGI
-IEncoder
 IEnum
 IExec
 IEXPLORE
@@ -960,7 +942,6 @@ imageresizerinput
 imageresizersettings
 imagingdevices
 ime
-IMetadata
 imeutil
 inetcpl
 Infobar
@@ -998,8 +979,6 @@ Interlop
 INTRESOURCE
 INVALIDARG
 invalidoperatioexception
-invalidkey
-IPalette
 ipc
 ipcmanager
 IPlugin
@@ -1008,8 +987,6 @@ IPREVIEW
 ipreviewhandlervisualssetfont
 IProperty
 IPublic
-IQuery
-IReader
 irprops
 isbi
 ISearch
@@ -1017,9 +994,7 @@ ISettings
 isfinite
 IShell
 isocpp
-ISource
 iss
-ISurface
 ITask
 ith
 ITHUMBNAIL
@@ -1130,8 +1105,6 @@ LOCALPACKAGE
 localport
 LOCALSYSTEM
 LOCATIONCHANGE
-LOCKBYTES
-LOCKTYPE
 LOGFONT
 LOGFONTW
 logon
@@ -1153,12 +1126,12 @@ LPCWSTR
 lpdw
 lpfn
 LPINPUT
-LPQUERY
 lpmi
 LPMINMAXINFO
 LPMONITORINFO
 LPOSVERSIONINFOEXW
 LPPOINT
+LPQUERY
 lprc
 LPRECT
 LPSAFEARRAY
@@ -1326,11 +1299,11 @@ Mul
 MULTIPLEUSE
 multizone
 mvvm
+mwb
+MWBEx
 myfile
 MYICON
 mysql
-mwb
-MWBEx
 NAMECHANGE
 nameof
 namespaceanddescendants
@@ -1403,7 +1376,6 @@ NONCONVERT
 NONELEVATED
 NONINFRINGEMENT
 nonstd
-NOOPEN
 NOOWNERZORDER
 NOPARENTNOTIFY
 NOREDIRECTIONBITMAP
@@ -1466,8 +1438,6 @@ OLEDB
 OLIVEGREEN
 onebranch
 onenote
-ONLYIFCURRENT
-ONLYONCE
 onstd
 oobe
 OOBEPT
@@ -1568,7 +1538,6 @@ pinvoke
 pipename
 PKBDLLHOOKSTRUCT
 pkey
-PKEY
 plib
 PLK
 ploc
@@ -1601,7 +1570,6 @@ ppidl
 ppmt
 pprm
 pproc
-pprop
 ppshv
 ppsi
 ppsid
@@ -1622,7 +1590,6 @@ previouscamera
 PREVIOUSINSTALLFOLDER
 PREVIOUSVERSIONSINSTALLED
 prevpane
-PRGBA
 prgms
 pri
 PRINTCLIENT
@@ -1639,9 +1606,7 @@ PROGRAMFILES
 projectname
 PROPBAG
 PROPERTYKEY
-PROPERTYNOTFOUND
 propkey
-PROPVARIANT
 propvarutil
 prvpane
 psapi
@@ -1651,8 +1616,6 @@ psfgao
 Psr
 psrm
 psrree
-pstatstg
-pstm
 pstr
 pstream
 pstrm
@@ -1666,7 +1629,6 @@ PToy
 ptstr
 pui
 PULONG
-pvar
 pwa
 pwcs
 pwsh
@@ -1706,6 +1668,7 @@ rclsid
 RCONTROL
 RCtrl
 READMODE
+READOBJECTS
 READWRITE
 RECTDESTINATION
 RECTL
@@ -1768,7 +1731,6 @@ resw
 resx
 retval
 rfc
-RGBE
 RGBQUAD
 rgbs
 rgelt
@@ -1811,7 +1773,6 @@ rungameid
 RUNLEVEL
 runsettings
 runtimeclass
-runtimeconfig
 runtimedepsjsonpath
 runtimeobject
 runtimepack
@@ -1827,7 +1788,6 @@ ryanbodrug
 saahmedm
 sachaple
 sacl
-SAFEARRAY
 safeprojectname
 SAMEKEYPREVIOUSLYMAPPED
 SAMESHORTCUTPREVIOUSLYMAPPED
@@ -1858,7 +1818,6 @@ sendvirtualinput
 Seperate
 Seraphima
 serverside
-Ses
 SETCONTEXT
 setcursor
 setenv
@@ -1947,7 +1906,6 @@ SMALLICON
 smartphone
 SMTO
 snd
-sni
 snwprintf
 softline
 somil
@@ -1975,7 +1933,6 @@ SRCPAINT
 sre
 SResize
 srf
-SRGB
 srme
 srre
 srw
@@ -2004,10 +1961,8 @@ STDMETHODCALLTYPE
 STDMETHODIMP
 stefan
 Stereolithography
-STGC
 STGM
 STGMEDIUM
-STGTY
 sticpl
 stl
 storelogo
@@ -2081,8 +2036,8 @@ taskschd
 tchar
 tcl
 Tcollab
-tcs
 tcp
+tcs
 tcscpy
 TCustom
 tdbuild
@@ -2165,6 +2120,7 @@ uipi
 UIs
 ULARGE
 ULONGLONG
+unapply
 unassign
 uncompilable
 UNCPRIORITY
@@ -2196,7 +2152,6 @@ Usb
 USEDEFAULT
 USEFILEATTRIBUTES
 USERDATA
-USERDEFINED
 USERDOMAIN
 userprofile
 USESHOWWINDOW
@@ -2213,7 +2168,6 @@ vabdq
 validmodulename
 Vanara
 variantassignment
-VARTYPE
 vcamp
 vccorlib
 vcdl
@@ -2233,7 +2187,6 @@ VERBSONLY
 VERBW
 VERIFYCONTEXT
 verrsrc
-VERSIONED
 VERSIONINFO
 Versioning
 VFT
@@ -2333,8 +2286,8 @@ winget
 wingetcreate
 Winhook
 winkey
-winlogon
 WINL
+winlogon
 winmd
 winmm
 WINNT
@@ -2391,6 +2344,7 @@ wregex
 WReserved
 WResize
 writefile
+WRITEOBJECTS
 Wrk
 wrl
 WSAEADDRINUSE
@@ -2402,7 +2356,6 @@ wsh
 wsl
 wss
 wstr
-wsystem
 wsz
 wtoi
 WTS
@@ -2446,7 +2399,6 @@ yinyue
 YOffset
 YPels
 ypescript
-YQuantized
 YResolution
 YStr
 YUY

installer/PowerToysSetupCustomActions/CustomAction.cpp

@@ -123,6 +123,8 @@ UINT __stdcall UnApplyModulesRegistryChangeSetsCA(MSIHANDLE hInstall)
         changeSet.unApply();
     }
 
+    SHChangeNotify(SHCNE_ASSOCCHANGED, SHCNF_IDLIST, NULL, NULL);
+
     ExitOnFailure(hr, "Failed to extract msix");
 
 LExit:

installer/PowerToysSetupCustomActions/stdafx.h

@@ -8,6 +8,7 @@
 #include <strsafe.h>
 #include <msiquery.h>
 #include <Msi.h>
+#include <shlobj_core.h>
 
 // WiX Header Files:
 #include <wcautil.h>

src/common/utils/modulesRegistry.h

@@ -192,6 +192,28 @@ inline registry::ChangeSet getStlThumbnailHandlerChangeSet(const std::wstring in
                                   NonLocalizable::ExtSTL);
 }
 
+inline registry::ChangeSet getRegistryPreviewSetDefaultAppChangeSet(const std::wstring installationDir, const bool perUser)
+{
+    const HKEY scope = perUser ? HKEY_CURRENT_USER : HKEY_LOCAL_MACHINE;
+
+    using vec_t = std::vector<registry::ValueChange>;
+    vec_t changes;
+
+    std::wstring appName = L"Registry Preview";
+    std::wstring fullAppName = L"PowerToys.RegistryPreview";
+    std::wstring registryKeyPrefix = L"Software\\Classes\\";
+
+    std::wstring appPath = installationDir + L"\\modules\\RegistryPreview\\PowerToys.RegistryPreview.exe";
+    std::wstring command = appPath + L" \"----ms-protocol:ms-encodedlaunch:App?ContractId=Windows.File&Verb=open&File=%1\"";
+
+    changes.push_back({ scope, registryKeyPrefix + fullAppName + L"\\" + L"Application", L"ApplicationName", appName });
+    changes.push_back({ scope, registryKeyPrefix + fullAppName + L"\\" + L"DefaultIcon", std::nullopt, appPath });
+    changes.push_back({ scope, registryKeyPrefix + fullAppName + L"\\" + L"shell\\open\\command", std::nullopt, command });
+    changes.push_back({ scope, registryKeyPrefix + L".reg\\OpenWithProgIDs", fullAppName, L"" });
+
+    return { changes };
+}
+
 inline registry::ChangeSet getRegistryPreviewChangeSet(const std::wstring installationDir,const bool perUser)
 {
     const HKEY scope = perUser ? HKEY_CURRENT_USER : HKEY_LOCAL_MACHINE;
@@ -235,5 +257,6 @@ inline std::vector<registry::ChangeSet> getAllModulesChangeSets(const std::wstri
              getPdfThumbnailHandlerChangeSet(installationDir, PER_USER),
              getGcodeThumbnailHandlerChangeSet(installationDir, PER_USER),
              getStlThumbnailHandlerChangeSet(installationDir, PER_USER),
-             getRegistryPreviewChangeSet(installationDir, PER_USER) };
+             getRegistryPreviewChangeSet(installationDir, PER_USER),
+             getRegistryPreviewSetDefaultAppChangeSet(installationDir, PER_USER) };
 }

src/modules/registrypreview/RegistryPreviewExt/dllmain.cpp

@@ -37,11 +37,19 @@ BOOL APIENTRY DllMain(HMODULE /*hModule*/, DWORD ul_reason_for_call, LPVOID /*lp
 const static wchar_t* MODULE_NAME = L"RegistryPreview";
 const static wchar_t* MODULE_DESC = L"A quick little utility to visualize and edit complex Windows Registry files.";
 
+namespace
+{
+    const wchar_t JSON_KEY_PROPERTIES[] = L"properties";
+    const wchar_t JSON_KEY_ENABLED[] = L"enabled";
+    const wchar_t JSON_KEY_DEFAULT_APP[] = L"default_reg_app";
+}
+
 class RegistryPreviewModule : public PowertoyModuleIface
 {
 
 private:
     bool m_enabled = false;
+    bool m_default_app = false;
 
     //Hotkey m_hotkey;
     HANDLE m_hProcess;
@@ -87,23 +95,70 @@ private:
         TerminateProcess(m_hProcess, 1);
     }
 
+    void parse_default_app_settings(PowerToysSettings::PowerToyValues settings)
+    {
+        const std::wstring installationDir = get_module_folderpath();
+        auto changeSet = getRegistryPreviewSetDefaultAppChangeSet(installationDir, true);
+
+        auto settingsObject = settings.get_raw_json();
+        if (settingsObject.GetView().Size())
+        {
+            auto default_app = settingsObject.GetNamedObject(JSON_KEY_PROPERTIES).GetNamedBoolean(JSON_KEY_DEFAULT_APP);
+
+            if (default_app != m_default_app)
+            {
+                m_default_app = default_app;
+                auto result = default_app ? changeSet.apply() : changeSet.unApply();
+
+                if (!result)
+                {
+                    Logger::error(L"Failed to {} default app registry change set.", default_app ? L"apply" : L"unapply");
+                }
+
+                SHChangeNotify(SHCNE_ASSOCCHANGED, SHCNF_IDLIST, NULL, NULL);
+            }
+        }
+        else
+        {
+            Logger::info("Registry Preview settings are empty");
+        }
+    }
+
+    // Load the settings file.
+    void init_settings()
+    {
+        try
+        {
+            // Load and parse the settings file for this PowerToy.
+            PowerToysSettings::PowerToyValues settings =
+                PowerToysSettings::PowerToyValues::load_from_settings_file(get_key());
+            
+            auto enabled = settings.get_bool_value(JSON_KEY_ENABLED);
+            auto result = true;
+            const std::wstring installationDir = get_module_folderpath();
+            auto enabledChangeSet = getRegistryPreviewChangeSet(installationDir, true);
+
+            result = enabled ? enabledChangeSet.apply() : enabledChangeSet.unApply();
+            if (!result)
+            {
+                Logger::error(L"Failed to {} enabled registry change set.", enabled ? L"apply" : L"unapply");
+            }
+
+            parse_default_app_settings(settings);
+        }
+        catch (std::exception&)
+        {
+            Logger::error("Invalid json when trying to load the Registry Preview settings json from file.");
+        }
+    }
+
 public:
     RegistryPreviewModule()
     {
         LoggerHelpers::init_logger(GET_RESOURCE_STRING(IDS_REGISTRYPREVIEW_NAME), L"ModuleInterface", "RegistryPreview");
         Logger::info("Registry Preview object is constructing");
 
-        if (!m_enabled)
-        {
-            const std::wstring installationDir = get_module_folderpath();
-
-            auto regChanges = getRegistryPreviewChangeSet(installationDir, true);
-
-            if (!regChanges.unApply())
-            {
-                Logger::error(L"Unapplying registry changes failed");
-            }
-        }
+        init_settings();
 
         triggerEvent = CreateEvent(nullptr, false, false, CommonSharedConstants::REGISTRY_PREVIEW_TRIGGER_EVENT);
         triggerEventWaiter = EventWaiter(CommonSharedConstants::REGISTRY_PREVIEW_TRIGGER_EVENT, [this](int) {
@@ -184,13 +239,13 @@ public:
             // Parse the input JSON string.
             PowerToysSettings::PowerToyValues values = PowerToysSettings::PowerToyValues::from_json_string(config, get_key());
 
-            // If you don't need to do any custom processing of the settings, proceed
-            // to persists the values.
+            parse_default_app_settings(values);
+
             values.save_to_settings_file();
         }
         catch (std::exception&)
         {
-            // Improper JSON.
+            Logger::error(L"Invalid json when trying to parse Registry Preview settings json.");
         }
     }
 
@@ -226,6 +281,8 @@ public:
             {
                 Logger::error(L"Unapplying registry changes failed");
             }
+
+            SHChangeNotify(SHCNE_ASSOCCHANGED, SHCNF_IDLIST, NULL, NULL);
         }
 
         m_enabled = false;

src/modules/registrypreview/RegistryPreviewUI/App.xaml.cs

@@ -6,6 +6,7 @@ using System;
 using System.Diagnostics;
 using System.Diagnostics.CodeAnalysis;
 using Microsoft.UI.Xaml;
+using Microsoft.Windows.AppLifecycle;
 using Windows.ApplicationModel.Activation;
 using LaunchActivatedEventArgs = Windows.ApplicationModel.Activation.LaunchActivatedEventArgs;
 
@@ -31,23 +32,47 @@ namespace RegistryPreview
         /// <param name="args">Details about the launch request and process.</param>
         protected override void OnLaunched(Microsoft.UI.Xaml.LaunchActivatedEventArgs args)
         {
-            // Grab the command line parameters directly from the Environment since this is expected to be run
-            // via Context Menu of a REG file.
-            string[] cmdArgs = Environment.GetCommandLineArgs();
-            if (cmdArgs == null)
+            // Keeping commented out but this is invaluable for protocol activation testing.
+            // #if DEBUG
+            // System.Diagnostics.Debugger.Launch();
+            // #endif
+
+            // Open With... handler - gets activation arguments if they are available.
+            AppActivationArguments activatedArgs = AppInstance.GetCurrent().GetActivatedEventArgs();
+            if (activatedArgs.Kind == ExtendedActivationKind.File)
             {
                 // Covers the double click exe scenario and treated as no file loaded
                 AppFilename = string.Empty;
-            }
-            else if (cmdArgs.Length == 2)
-            {
-                // GetCommandLineArgs() send in the called EXE as 0 and the selected filename as 1
-                AppFilename = cmdArgs[1];
+                if (activatedArgs.Data != null)
+                {
+                    IFileActivatedEventArgs eventArgs = (IFileActivatedEventArgs)activatedArgs.Data;
+                    if (eventArgs.Files.Count > 0)
+                    {
+                        AppFilename = eventArgs.Files[0].Path;
+                    }
+                }
             }
             else
             {
-                // Anything else should be treated as no file loaded
-                AppFilename = string.Empty;
+                // Right click on a REG file and selected Preview
+                // Grab the command line parameters directly from the Environment since this is expected to be run
+                // via Context Menu of a REG file.
+                string[] cmdArgs = Environment.GetCommandLineArgs();
+                if (cmdArgs == null)
+                {
+                    // Covers the double click exe scenario and treated as no file loaded
+                    AppFilename = string.Empty;
+                }
+                else if (cmdArgs.Length == 2)
+                {
+                    // GetCommandLineArgs() send in the called EXE as 0 and the selected filename as 1
+                    AppFilename = cmdArgs[1];
+                }
+                else
+                {
+                    // Anything else should be treated as no file loaded
+                    AppFilename = string.Empty;
+                }
             }
 
             // Start the application

src/settings-ui/Settings.UI.Library/RegistryPreviewProperties.cs

@@ -0,0 +1,19 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Text.Json.Serialization;
+
+namespace Microsoft.PowerToys.Settings.UI.Library
+{
+    public class RegistryPreviewProperties
+    {
+        public RegistryPreviewProperties()
+        {
+            DefaultRegApp = false;
+        }
+
+        [JsonPropertyName("default_reg_app")]
+        public bool DefaultRegApp { get; set; }
+    }
+}

src/settings-ui/Settings.UI.Library/RegistryPreviewSettings.cs

@@ -11,8 +11,12 @@ namespace Microsoft.PowerToys.Settings.UI.Library
     {
         public const string ModuleName = "RegistryPreview";
 
+        [JsonPropertyName("properties")]
+        public RegistryPreviewProperties Properties { get; set; }
+
         public RegistryPreviewSettings()
         {
+            Properties = new RegistryPreviewProperties();
             Version = "1";
             Name = ModuleName;
         }

src/settings-ui/Settings.UI.Library/SndRegistryPreviewSettings.cs

@@ -0,0 +1,29 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Text.Json;
+using System.Text.Json.Serialization;
+
+namespace Microsoft.PowerToys.Settings.UI.Library
+{
+    public class SndRegistryPreviewSettings
+    {
+        [JsonPropertyName("RegistryPreview")]
+        public RegistryPreviewSettings RegistryPreview { get; set; }
+
+        public SndRegistryPreviewSettings()
+        {
+        }
+
+        public SndRegistryPreviewSettings(RegistryPreviewSettings settings)
+        {
+            RegistryPreview = settings;
+        }
+
+        public string ToJsonString()
+        {
+            return JsonSerializer.Serialize(this);
+        }
+    }
+}

src/settings-ui/Settings.UI/Strings/en-us/Resources.resw

@@ -3502,6 +3502,13 @@ Activate by holding the key for the character you want to add an accent to, then
   <data name="RegistryPreview_LaunchButtonControl.Header" xml:space="preserve">
     <value>Launch Registry Preview</value>
   </data>
+  <data name="RegistryPreview_DefaultRegApp.Header" xml:space="preserve">
+    <value>Default app</value>
+  </data>
+  <data name="RegistryPreview_DefaultRegApp.Description" xml:space="preserve">
+    <value>Make Registry Preview default app for opening .reg files</value>
+    <comment>Registry Preview is app name. Do not localize.</comment>
+  </data>
   <data name="PastePlain_ShortcutWarning.Title" xml:space="preserve">
     <value>Using this shortcut may prevent non-text paste actions (e.g. images, files) or built-in paste plain text actions in other applications from functioning.</value>
   </data>

src/settings-ui/Settings.UI/ViewModels/RegistryPreviewViewModel.cs

@@ -3,6 +3,8 @@
 // See the LICENSE file in the project root for more information.
 
 using System;
+using System.Globalization;
+using System.Text.Json;
 using global::PowerToys.GPOWrapper;
 using Microsoft.PowerToys.Settings.UI.Library;
 using Microsoft.PowerToys.Settings.UI.Library.Helpers;
@@ -17,7 +19,7 @@ namespace Microsoft.PowerToys.Settings.UI.ViewModels
 
         public ButtonClickCommand LaunchEventHandler => new ButtonClickCommand(Launch);
 
-        public RegistryPreviewViewModel(ISettingsRepository<GeneralSettings> settingsRepository, Func<string, int> ipcMSGCallBackFunc)
+        public RegistryPreviewViewModel(ISettingsRepository<GeneralSettings> settingsRepository, ISettingsRepository<RegistryPreviewSettings> registryPreviewSettingsRepository, Func<string, int> ipcMSGCallBackFunc)
         {
             // To obtain the general settings configurations of PowerToys Settings.
             if (settingsRepository == null)
@@ -27,6 +29,8 @@ namespace Microsoft.PowerToys.Settings.UI.ViewModels
 
             GeneralSettingsConfig = settingsRepository.SettingsConfig;
 
+            _settings = registryPreviewSettingsRepository.SettingsConfig;
+
             InitializeEnabledValue();
 
             // set the callback functions value to hangle outgoing IPC message.
@@ -71,6 +75,21 @@ namespace Microsoft.PowerToys.Settings.UI.ViewModels
             }
         }
 
+        public bool IsRegistryPreviewDefaultRegApp
+        {
+            get => _settings.Properties.DefaultRegApp;
+            set
+            {
+                if (_settings.Properties.DefaultRegApp != value)
+                {
+                    _settings.Properties.DefaultRegApp = value;
+                    OnPropertyChanged(nameof(IsRegistryPreviewDefaultRegApp));
+
+                    NotifySettingsChanged();
+                }
+            }
+        }
+
         public bool IsEnabledGpoConfigured
         {
             get => _enabledStateIsGPOConfigured;
@@ -88,11 +107,23 @@ namespace Microsoft.PowerToys.Settings.UI.ViewModels
         private GpoRuleConfigured _enabledGpoRuleConfiguration;
         private bool _enabledStateIsGPOConfigured;
         private bool _isRegistryPreviewEnabled;
+        private RegistryPreviewSettings _settings;
 
         public void RefreshEnabledState()
         {
             InitializeEnabledValue();
             OnPropertyChanged(nameof(IsRegistryPreviewEnabled));
         }
+
+        private void NotifySettingsChanged()
+        {
+            // Using InvariantCulture as this is an IPC message
+            SendConfigMSG(
+                   string.Format(
+                       CultureInfo.InvariantCulture,
+                       "{{ \"powertoys\": {{ \"{0}\": {1} }} }}",
+                       RegistryPreviewSettings.ModuleName,
+                       JsonSerializer.Serialize(_settings)));
+        }
     }
 }

src/settings-ui/Settings.UI/Views/RegistryPreviewPage.xaml

@@ -11,11 +11,9 @@
     AutomationProperties.LandmarkType="Main"
     mc:Ignorable="d">
 
-    <controls:SettingsPageControl
-        x:Uid="RegistryPreview"
-        ModuleImageSource="ms-appx:///Assets/Modules/RegistryPreview.png">
+    <controls:SettingsPageControl x:Uid="RegistryPreview" ModuleImageSource="ms-appx:///Assets/Modules/RegistryPreview.png">
         <controls:SettingsPageControl.ModuleContent>
-            <StackPanel Orientation="Vertical" ChildrenTransitions="{StaticResource SettingsCardsAnimations}">
+            <StackPanel ChildrenTransitions="{StaticResource SettingsCardsAnimations}" Orientation="Vertical">
                 <labs:SettingsCard
                     x:Uid="RegistryPreview_Enable_RegistryPreview"
                     HeaderIcon="{ui:BitmapIcon Source=/Assets/FluentIcons/FluentIconsRegistryPreview.png}"
@@ -40,15 +38,17 @@
                         HeaderIcon="{ui:FontIcon FontFamily={StaticResource SymbolThemeFontFamily},
                                                  Glyph=&#xEA37;}"
                         IsClickEnabled="True" />
+
+                    <labs:SettingsCard x:Uid="RegistryPreview_DefaultRegApp" HeaderIcon="{ui:FontIcon FontFamily={StaticResource SymbolThemeFontFamily}, Glyph=&#xE7AC;}">
+                        <ToggleSwitch x:Uid="RegistryPreview_DefaultRegApp_ToggleSwitch" IsOn="{x:Bind Mode=TwoWay, Path=ViewModel.IsRegistryPreviewDefaultRegApp}" />
+                    </labs:SettingsCard>
                 </controls:SettingsGroup>
 
             </StackPanel>
         </controls:SettingsPageControl.ModuleContent>
-        
+
         <controls:SettingsPageControl.PrimaryLinks>
-            <controls:PageLink
-                x:Uid="LearnMore_RegistryPreview"
-                Link="https://aka.ms/PowerToysOverview_RegistryPreview" />
+            <controls:PageLink x:Uid="LearnMore_RegistryPreview" Link="https://aka.ms/PowerToysOverview_RegistryPreview" />
         </controls:SettingsPageControl.PrimaryLinks>
     </controls:SettingsPageControl>
 </Page>

src/settings-ui/Settings.UI/Views/RegistryPreviewPage.xaml.cs

@@ -16,7 +16,10 @@ namespace Microsoft.PowerToys.Settings.UI.Views
         public RegistryPreviewPage()
         {
             var settingsUtils = new SettingsUtils();
-            ViewModel = new RegistryPreviewViewModel(SettingsRepository<GeneralSettings>.GetInstance(settingsUtils), ShellPage.SendDefaultIPCMessage);
+            ViewModel = new RegistryPreviewViewModel(
+                SettingsRepository<GeneralSettings>.GetInstance(settingsUtils),
+                SettingsRepository<RegistryPreviewSettings>.GetInstance(settingsUtils),
+                ShellPage.SendDefaultIPCMessage);
             DataContext = ViewModel;
             InitializeComponent();
         }