Support wcwidth_l with xlocale_wrapper.

Author: zaneenders

Package.swift

@@ -20,12 +20,14 @@ let _: Package =
         ],
         targets: [
           .target(name: "libunistring"),
+          .target(name: "xlocale_wrapper"),
           .target(name: "Geometry"),
           .target(name: "Primitives"),
           .target(name: "VirtualTerminal", dependencies: [
             .target(name: "Geometry"),
             .target(name: "Primitives"),
             .target(name: "libunistring", condition: .when(traits: ["GNU"])),
+            .target(name: "xlocale_wrapper"),
             .product(name: "POSIXCore", package: "swift-platform-core", condition: .when(platforms: [.macOS, .linux])),
             .product(name: "WindowsCore", package: "swift-platform-core", condition: .when(platforms: [.windows])),
           ]),

Sources/VirtualTerminal/Buffer/TextMetrics.swift

@@ -4,12 +4,22 @@
 #if os(Windows)
 import WindowsCore
 #else
+import POSIXCore
+import Synchronization
+#if canImport(Darwin)
+import Darwin
+import xlocale_wrapper
+#elseif canImport(Glibc)
+import Glibc
+#endif
 #if GNU
 import libunistring
 #endif
 import POSIXCore
 import Synchronization
+#endif
 
+#if canImport(Glibc)
 private enum Locale {
   private static let utf8: Mutex<locale_t?> = Mutex(nil)
 
@@ -21,7 +31,18 @@ private enum Locale {
     }
   }
 }
+#elseif canImport(Darwin)
+private enum Locale {
+  private static let utf8: Mutex<UnsafeMutableRawPointer?> = Mutex(nil)
 
+  static var ID_UTF8: UnsafeMutableRawPointer? {
+    return utf8.withLock { locale in
+      if let locale { return locale }
+      locale = vt_newlocale(LC_CTYPE_MASK, "en_US.UTF-8", nil)
+      return locale
+    }
+  }
+}
 #endif
 
 extension UnicodeScalar {
@@ -87,12 +108,14 @@ extension UnicodeScalar {
     // Normal width character                       -> 1
     // Wide character (CJK, etc.)                   -> 2
     return max(1, Int(uc_width(UInt32(value), "C.UTF-8")))
-#else
+#elseif canImport(Glibc)
     // Control character or invalid - zero width    -> -1
     // Zero-width character (combining marks, etc.) -> 0
     // Normal width character                       -> 1
     // Wide character (CJK, etc.)                   -> 2
     return max(1, Int(wcwidth_l(wchar_t(value), Locale.ID_UTF8)))
+#else
+    return max(1, Int(vt_wcwidth_l(wchar_t(value), Locale.ID_UTF8)))
 #endif
   }
 }

Sources/VirtualTerminal/Platform/POSIXTerminal.swift

@@ -6,6 +6,9 @@
 import Geometry
 import POSIXCore
 import Synchronization
+#if !GNU
+import unistd
+#endif
 
 /// POSIX/Unix terminal implementation using standard file descriptors.
 ///

Sources/xlocale_wrapper/include/xlocale_wrapper.h

@@ -0,0 +1,27 @@
+/* Copyright © 2025 Saleem Abdulrasool <compnerd@compnerd.org> */
+/* SPDX-License-Identifier: BSD-3-Clause */
+
+#ifndef xlocale_wrapper_h
+#define xlocale_wrapper_h
+
+#include <wchar.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+// Wrapper functions for xlocale functionality
+int vt_wcwidth_l(wchar_t wc, void *locale);
+void *vt_newlocale(int mask, const char *locale, void *base);
+void vt_freelocale(void *locale);
+
+// Constants
+#if __APPLE__
+#define LC_CTYPE_MASK (1 << 1)
+#endif
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* xlocale_wrapper_h */

Sources/xlocale_wrapper/xlocale_wrapper.c

@@ -0,0 +1,21 @@
+/* Copyright © 2025 Saleem Abdulrasool <compnerd@compnerd.org> */
+/* SPDX-License-Identifier: BSD-3-Clause */
+
+#include <wchar.h>
+#include <xlocale.h>
+
+int vt_wcwidth_l(wchar_t wc, void *locale) {
+    return wcwidth_l(wc, (locale_t)locale);
+}
+
+void *vt_newlocale(int mask, const char *locale, void *base) {
+    return newlocale(mask, locale, (locale_t)base);
+}
+
+void vt_freelocale(void *locale) {
+    freelocale((locale_t)locale);
+}
+
+#if __APPLE__
+#define LC_CTYPE_MASK (1 << 1)
+#endif