docs: add WebView2 package reference documentation

docs/PackageReference/Webview2/README.md

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+---
+title: Documentation Overview
+parent: WebView2 Package
+nav_order: 2
+---
+
+# WebView2 Technical Documentation
+
+twinBASIC WebView2 package provides complete Microsoft Edge WebView2 control integration, enabling you to embed modern web content in twinBASIC applications and achieve bidirectional interaction.
+
+## Documentation Index
+
+### Core Documents
+
+| Document                             | Description                                    |
+| ------------------------------------ | ---------------------------------------------- |
+| [Getting Started Guide](./Getting-started.md) | Quick start with WebView2 control              |
+| [Index](./index.md)                  | Documentation index and functionality overview |
+
+### Class References
+
+| Document                                        | Description                                  |
+| ----------------------------------------------- | -------------------------------------------- |
+| [WebView2 Control](./WebView2.md)              | Main control class, complete reference of all properties, methods, and events |
+| [Environment Options](./WebView2EnvironmentOptions.md) | WebView2 environment configuration options   |
+
+### HTTP Related
+
+| Document                                     | Description               |
+| -------------------------------------------- | ------------------------- |
+| [HTTP Request](./WebView2Request.md)         | Web resource request object|
+| [HTTP Response](./WebView2Response.md)       | Web resource response object|
+| [Request Headers](./WebView2RequestHeaders.md)| HTTP request header management |
+| [Response Headers](./WebView2ResponseHeaders.md)| HTTP response header management|
+| [Header Collection](./WebView2HeadersCollection.md)| HTTP header collection enumeration |
+| [Header Info](./WebView2Header.md)           | Single HTTP header information |
+
+### Advanced Topics
+
+| Document                             | Description                                 |
+| ------------------------------------ | ------------------------------------------- |
+| [Enumeration Types](./WebView2-Enumerations.md)| All enumeration type definitions and descriptions |
+| [Deferred Callback](./DeferredCallback.md) | Deferred event and callback mechanism (re-entrancy issues) |
+
+## Quick Navigation
+
+### I Want to...
+
+#### Display a Web Page
+
+```vb
+WebView21.Navigate "https://www.example.com"
+```
+
+→ Refer to [WebView2 Control - Navigation Methods](./WebView2.md#navigation-methods)
+
+#### Execute JavaScript
+
+```vb
+Dim result As Variant
+result = WebView21.JsRun("document.title")
+```
+
+→ Refer to [WebView2 Control - JavaScript Interaction](./WebView2.md#javascript-interaction)
+
+#### Communicate Between Twinbasic and JavaScript
+
+```vb
+' Twinbasic sends to JavaScript
+WebView21.PostWebMessage "Hello!"
+
+' JavaScript sends to Twinbasic
+window.chrome.webview.postMessage("Hello from JS");
+```
+
+→ Refer to [WebView2 Control - Message Passing](./WebView2.md#javascript-interaction)
+
+#### Intercept HTTP Requests
+
+```vb
+WebView21.AddWebResourceRequestedFilter "*://*/*.png", wv2Image
+
+Private Sub WebView21_WebResourceRequested(ByVal Request As WebView2Request, _
+    ByVal Response As WebView2Response)
+    ' Handle request
+End Sub
+```
+
+→ Refer to [WebView2 Control - Web Resource Interception](./WebView2.md#resource-management)
+
+#### Customize Right-Click Menu
+
+```vb
+Private Sub WebView21_UserContextMenu(X As Single, Y As Single)
+    PopupMenu mnuCustomContext, vbPopupMenuRightButton, X, Y
+End Sub
+```
+
+→ Refer to [WebView2 Control - Events](./WebView2.md#user-interaction-events)
+
+#### Print to PDF
+
+```vb
+WebView21.PrintToPdf "C:\output.pdf"
+```
+
+→ Refer to [WebView2 Control - Advanced Features](./WebView2.md#advanced-features)
+
+#### Configure Environment Options
+
+```vb
+WebView21.EnvironmentOptions.UserDataFolder = "C:\MyApp\Data"
+WebView21.EnvironmentOptions.Language = "en-US"
+```
+
+→ Refer to [Environment Options](./WebView2EnvironmentOptions.md)
+
+## Core Class Diagram
+
+```
+WebView2 (Main Control)
+├── WebView2EnvironmentOptions (Environment Configuration)
+├── WebView2Request (HTTP Request)
+│   └── WebView2RequestHeaders (Request Headers)
+│       └── WebView2HeadersCollection (Header Collection)
+│           └── WebView2Header (Single Header)
+└── WebView2Response (HTTP Response)
+    └── WebView2ResponseHeaders (Response Headers)
+        └── WebView2HeadersCollection (Header Collection)
+            └── WebView2Header (Single Header)
+```
+
+## Main Functionality Modules
+
+### 1. Web Content Display
+
+- ✅ Load URL web pages
+- ✅ Load custom HTML strings
+- ✅ Virtual host mapping
+- ✅ PDF export
+
+### 2. Navigation Control
+
+- ✅ Forward/backward navigation
+- ✅ Page refresh
+- ✅ Custom HTTP requests (POST, Headers)
+
+### 3. JavaScript Interaction
+
+- ✅ Execute JavaScript code
+- ✅ Synchronously call JS functions
+- ✅ Asynchronously call JS functions
+- ✅ Bidirectional message passing
+
+### 4. Object Sharing
+
+- ✅ Expose COM objects to JavaScript
+- ✅ Deferred invocation mode (avoid re-entrancy)
+
+### 5. Event Handling
+
+- ✅ Navigation events
+- ✅ Permission request events
+- ✅ Script dialog events
+- ✅ Download events
+- ✅ Web resource interception
+
+### 6. Advanced Features
+
+- ✅ Developer tools
+- ✅ DevTools protocol
+- ✅ Download manager
+- ✅ Task manager
+- ✅ Audio control
+- ✅ Suspend/resume
+
+## Development Workflow
+
+### Step 1: Environment Setup
+
+1. Install WebView2 Runtime
+2. Reference WebView2 package
+3. Add WebView2 control to form
+
+→ Refer to [Getting Started](./Getting-started.md)
+
+### Step 2: Basic Navigation
+
+```vb
+Private Sub Form_Load()
+    ' Note: All WebView21 member operations must be done after WebView21_Ready()
+End Sub
+
+Private Sub WebView21_Ready()
+    WebView21.DocumentURL = "https://www.example.com"
+End Sub
+
+Private Sub WebView21_NavigationComplete(ByVal IsSuccess As Boolean, _
+    ByVal WebErrorStatus As Long)
+    ' Page loading complete
+End Sub
+```
+
+### Step 3: JavaScript Interaction
+
+```vb
+' Execute JS
+WebView21.ExecuteScript "document.body.style.background = 'red'"
+
+' Get JS return value
+Dim title As Variant
+title = WebView21.JsProp("document.title")
+```
+
+### Step 4: Bidirectional Communication
+
+```vb
+' Twinbasic sends to JavaScript
+WebView21.PostWebMessage "Hello"
+
+Private Sub WebView21_JsMessage(ByVal Message As Variant)
+    ' Receive JavaScript message
+End Sub
+```
+
+### Step 5: Advanced Features
+
+- Intercept HTTP requests
+- Customize right-click menu
+- Print PDF
+- Virtual host mapping
+
+## Common Questions
+
+### 1. Control Not Displaying
+
+Make sure to set `Visible = True` and properly set position and size.
+
+### 2. Page Loading Failed
+
+Check if WebView2 Runtime is installed and review the `Error` event.
+
+### 3. JavaScript Call Timeout
+
+Set `JsCallTimeOutSeconds` property to increase timeout.
+
+### 4. Re-entrancy Problems
+
+Use `UseDeferredEvents = True` and use `UseDeferredInvoke = True` in `AddObject`.
+
+### 5. Permission Requests
+
+Handle permission requests in the `PermissionRequested` event.
+
+## Dependency Requirements
+
+- Windows 7 SP1 or higher
+- WebView2 Runtime (Evergreen) 86.0.616.0 or higher
+
+## License
+
+The WebView2 package follows its own license terms, see the LICENCE.md file in the package for details.
+
+## Feedback and Support
+
+For questions or suggestions, please provide feedback through:
+
+- Submit an Issue
+- Visit twinBASIC community
+
+## Documentation Updates
+
+Last updated: February 15, 2026