Separator: uses widecharwidth for Unicode wcwidth and fixes issue that wchar_t on Windows is 2-byte length

src/util/wcwidth.c

@@ -0,0 +1,32 @@
+#include "wcwidth.h"
+#include "3rdparty/widecharwidth/widechar_width_c.h"
+
+int mk_wcwidth(uint32_t wc)
+{
+    // // We render U+1F6E1 (🛡) with a width of 2,
+    // // but widechar_width says it has a width of 1 because Unicode classifies it as "neutral".
+    // //
+    // // So we simply decide the width ourselves
+    // if (wc == 0x1F6E1) return 2;
+    //
+    // Well terminals do show it as width 1 after all
+
+    int width = widechar_wcwidth(wc);
+
+    switch (width) {
+        case widechar_ambiguous:
+        case widechar_private_use:
+            return 1;
+        case widechar_widened_in_9:
+            // Our renderer supports Unicode 9
+            return 2;
+        // case widechar_nonprint:
+        // case widechar_combining:
+        // case widechar_unassigned:
+        // case widechar_non_character:
+        //    return -1;
+        default:
+            // Use the width widechar_width gave us.
+            return width;
+    }
+}

src/util/wcwidth.h

@@ -1,16 +1,16 @@
 #pragma once
 
-#include <wchar.h>
+#include <stdint.h>
 
 #ifdef FF_HAVE_WCWIDTH
-static inline int mk_wcwidth(wchar_t ucs) {
-    return wcwidth(ucs);
-}
-static inline int mk_wcswidth(const wchar_t *pwcs, size_t n) {
-    return wcswidth(pwcs, n);
+#include <wchar.h>
+
+// Should be char32_t but it's not defined on macOS
+static_assert(sizeof(wchar_t) == sizeof(uint32_t), "wcwidth implementation requires wchar_t to be 32 bits");
+
+static inline int mk_wcwidth(uint32_t ucs) {
+    return wcwidth((wchar_t) ucs);
 }
 #else
-// https://www.cl.cam.ac.uk/~mgk25/ucs/wcwidth.c
-int mk_wcwidth(wchar_t ucs);
-int mk_wcswidth(const wchar_t *pwcs, size_t n);
+int mk_wcwidth(uint32_t wc);
 #endif