fix: set system language to webview on windows, closes #442 (#640)

* fix: set system language to webview on windows

* Update .changes/i18n-windows.md

Co-authored-by: Amr Bashir <amr.bashir2015@gmail.com>

.changes/i18n-windows.md

@@ -0,0 +1,5 @@
+---
+"wry": patch
+---
+
+Set webview2 language to match the OS language. This makes i18n functions like `new Date().toLocaleStrin()` behave correctly. 

Cargo.toml

@@ -74,7 +74,8 @@ windows-implement = "0.37.0"
   "Win32_System_SystemInformation",
   "Win32_System_SystemServices",
   "Win32_UI_Shell",
-  "Win32_UI_WindowsAndMessaging"
+  "Win32_UI_WindowsAndMessaging",
+  "Win32_Globalization"
 ]
 
 [target."cfg(any(target_os = \"ios\", target_os = \"macos\"))".dependencies]

src/webview/webview2/mod.rs

@@ -19,6 +19,7 @@ use windows::{
   core::{Interface, PCWSTR, PWSTR},
   Win32::{
     Foundation::{BOOL, E_FAIL, E_POINTER, FARPROC, HWND, LPARAM, LRESULT, POINT, RECT, WPARAM},
+    Globalization::{self, MAX_LOCALE_NAME},
     System::{
       Com::{IStream, StructuredStorage::CreateStreamOnHGlobal},
       LibraryLoader::{GetProcAddress, LoadLibraryA},
@@ -95,8 +96,24 @@ impl InnerWebView {
 
     CreateCoreWebView2EnvironmentCompletedHandler::wait_for_async_operation(
       Box::new(move |environmentcreatedhandler| unsafe {
-        let options: ICoreWebView2EnvironmentOptions =
-          CoreWebView2EnvironmentOptions::default().into();
+        let options = {
+          let options: ICoreWebView2EnvironmentOptions =
+            CoreWebView2EnvironmentOptions::default().into();
+
+          // Get user's system language
+          let lcid = Globalization::GetUserDefaultUILanguage();
+          let mut lang = [0; MAX_LOCALE_NAME as usize];
+          Globalization::LCIDToLocaleName(
+            lcid as u32,
+            &mut lang,
+            Globalization::LOCALE_ALLOW_NEUTRAL_NAMES,
+          );
+
+          options
+            .SetLanguage(PCWSTR(lang.as_ptr()))
+            .map_err(webview2_com::Error::WindowsError)?;
+          options
+        };
 
         // remove "mini menu" - See https://github.com/tauri-apps/wry/issues/535
         let _ = options.SetAdditionalBrowserArguments("--disable-features=msWebOOUI,msPdfOOUI");