adding draft for locale api review

Author: srwei

specs/LocaleRegion.md

@@ -0,0 +1,92 @@
+LocaleRegion
+===
+
+# Background
+Developers have requested access to programmatically choose the specific locale/region to use in WebView2. 
+The locale/region updates the JavaScript region (objects in the ECMA standard) which gets reflected as
+variations in time and date formats. Currently, the locale is by default set to the same value as the 
+display language. 
+
+You can use the `LocaleRegion` API to update the locale value individually from the display
+language.
+
+# Description
+* The intended value for `LocaleRegion` is in the format of `language[-country]` where `language` is the 
+2-letter code from [ISO 639](https://www.iso.org/iso-639-language-codes.html) and `country` is the 
+2-letter code from [ISO 3166](https://www.iso.org/standard/72482.html).
+* By default, the `LocaleRegion` will be set as the value for the Limited option in the browser.
+That means that if the OS region and the display language share the same language code, 
+like 'en-GB' and 'en-US', the value will be set to the OS region.
+
+# Examples
+```cpp
+auto webViewEnvironment10 = m_webViewEnvironment.try_query<ICoreWebView2Environment10>();
+wil::com_ptr<ICoreWebView2ControllerOptions> options;
+HRESULT hr = webViewEnvironment10->CreateCoreWebView2ControllerOptions(&options);
+options->put_LocaleRegion(m_webviewOption.localeRegion.c_str());
+```
+
+```c#
+CoreWebView2Environment _webViewEnvironment;
+WebViewCreationOptions _creationOptions;
+public CreateWebView2Controller(IntPtr parentWindow)
+{
+    CoreWebView2ControllerOptions controllerOptions = new CoreWebView2ControllerOptions();
+    controllerOptions.LocaleRegion = _creationOptions.localeRegion;
+    CoreWebView2Controller controller = null;
+    if (_creationOptions.entry == WebViewCreateEntry.CREATE_WITH_OPTION)
+    {
+        controller = await _webViewEnvironment.CreateCoreWebView2ControllerAsync(parentWindow, options);
+    }
+    else
+    {
+        controller = await _webViewEnvironment.CreateCoreWebView2ControllerAsync(parentWindow);
+    }
+    // update locale with value
+    SetAppLocale(localeRegion);
+}
+```
+
+# API Details
+```cpp
+[uuid(0c9a374f-20c3-4e3c-a640-67b78a7e0a48), object, pointer_default(unique)]
+interface ICoreWebView2ControllerOptions : IUnknown {
+  /// Interface for locale region that is updated through the ControllerOptions
+  /// API.
+  /// The default region for WebView.  It applies to browser UI such as
+  /// in the time/date formats. The intended locale value is in the format of
+  /// `language[-country]` where `language` is the 2-letter code from [ISO
+  /// 639](https://www.iso.org/iso-639-language-codes.html) and `country` is the
+  /// 2-letter code from [ISO 3166](https://www.iso.org/standard/72482.html).
+  ///
+  /// Validation is done on the V8 engine to match on the closest locale
+  /// from the passed in locale region value. For example, passing in "en_gb"
+  /// will reflect the "en-GB" locale in V8.
+  /// If V8 cannot find any matching locale on the input value, it will default
+  /// to the display language as the locale.
+  ///
+  /// The caller must free the returned string with `CoTaskMemFree`.  See
+  /// [API Conventions](/microsoft-edge/webview2/concepts/win32-api-conventions#strings).
+  /// \snippet AppWindow.cpp RegionLocaleSetting
+  // MSOWNERS: [email protected]
+  [propget] HRESULT LocaleRegion([out, retval] LPWSTR* locale);
+
+  /// Sets the `Region` property.
+  // MSOWNERS: [email protected]
+  [propput] HRESULT LocaleRegion([in] LPCWSTR locale);
+}
+```
+
+```c#
+namespace Microsoft.Web.WebView2.Core
+{
+    runtimeclass CoreWebView2ControllerOptions
+    {        
+       // ...
+       [interface_name("Microsoft.Web.WebView2.Core.ICoreWebView2ControllerOptions")]
+       {
+
+           String LocaleRegion { get; set; };
+       }
+    }
+}