# File Explorer ## End user facing: [Please visit our overview](https://aka.ms/PowerToysOverview_FileExplorerAddOns) ## Developing We have already done most of the development work in the [PreviewHandlerCommon](./common/cominterop/IPreviewHandler.cs) common project. To add a preview for the file type of .xyz: - Add a new .NET project in the preview pane folder. - Add a reference to the `PreviewHandlerCommon` common project. - Create your preview handler class and extend the FileBasedPreviewHandler class. See an example below: ```csharp using System; using System.Runtime.InteropServices; using Common; namespace XYZPreviewHandler { /// /// Implementation of preview handler for .xyz files. /// GUID = CLSID / CLASS ID. /// [Guid("xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxx")] [ClassInterface(ClassInterfaceType.None)] [ComVisible(true)] public class XYZPreviewHandler : FileBasedPreviewHandler { private XYZPreviewHandlerControl xyzPreviewHandlerControl; /// Call your rendering method here. public override void DoPreview() { this.xyzPreviewHandlerControl.DoPreview(this.FilePath); } protected override IPreviewHandlerControl CreatePreviewHandlerControl() { this.xyzPreviewHandlerControl = new xyzPreviewHandlerControl(); return this.xyzPreviewHandlerControl; } } } ``` Create a separate Preview Handler Control class and extend the `FormHandlerControl` Class. ```csharp using Common; namespace XYZPreviewHandler { public class XYZPreviewHandlerControl : FormHandlerControl { public XYZPreviewHandlerControl() { // ... do your initializations here. } public override void DoPreview(T dataSource) { // ... add your preview rendering code here. } } } ``` #### Integrate the Preview Handler into PowerToys Settings: Navigate to the [powerpreview](../previewpane/powerpreview/powerpreview.h) project and edit the `powerpreview.h` file. Add the following Settings Object instance to `m_previewHandlers` settings objects array in the constructor initialization: ```cpp // XYZ Preview Handler Settings Object. FileExplorerPreviewSettings( false, L"<--YOUR_TOGGLE_CONTROL_ID-->", L"<--A description of your preview handler-->", L"xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxx", // your preview handler CLSID. L"<--A display name for your preview handler-->") ``` ## Installation ### MSI (Recommended) To add a new Previewer update the `Product.wxs` file in `PowerToysSetup` similar to existing Previewer to register the Preview Handler. More details about registration of Preview Handlers can be [found here.](https://docs.microsoft.com/en-us/windows/win32/shell/how-to-register-a-preview-handler) ```xml ``` ### Directly registering/unregistering DLL's **[Important] This method of registering Preview Handler DLL's is not recommended. It could lead to registry corruption.** #### Registering Preview Handler 1. Restart Visual studio as administrator. 2. Sign `XYZPreviewHandler` and it's dependencies. To sign an assembly in VS, follow steps given [here](https://docs.microsoft.com/en-us/dotnet/standard/assembly/sign-strong-name#create-and-sign-an-assembly-with-a-strong-name-by-using-visual-studio). 3. Build `XYZPreviewHandler` project. 4. Open developer command prompt from `Tools > Command Line > Developer Command Prompt`. 5. Run following command for each nuget and project dependency to add them to Global Assembly Cache(GAC). ``` gacutil -i ``` 6. Run following commands to register preview handler. ``` cd C:\Windows\Microsoft.NET\Framework64\4.0.x.x gacutil -i RegAsm.exe /codebase ``` 7. Restart Windows Explorer process. #### Unregistering Preview Handler 1. Run following commands in elevated developer command prompt to unregister preview handler. ``` cd C:\Windows\Microsoft.NET\Framework64\4.0.x.x RegAsm.exe /unregister gacutil -u XYZPreviewHandler ``` ## Debugging Since in-process preview handlers run under a surrogate hosting process (prevhost.exe by default), to debug a preview handler, you need to attach the debugger to the host process. 1. Click on a file with registered extension to start host process. 2. Attach debugger in Visual studio from `Debug->Attach to Process` and select `prevhost.exe` with type `Managed(version), x64`. ## Managing Preview Handlers After successful integration, your preview handler should appear in the PowerToys settings UI under the `File Explorer Preview` Tab. In here you should be able to enable and disable all the preview handles. Settings UI - File Explorer Preview Tab