Use wcwidth implementation from fish-shell

.clang-format-ignore

@@ -0,0 +1 @@
+src/util/widechar_width.h

.gitattributes

@@ -1 +1,2 @@
 * text=true
+src/util/widechar_width.h linguist-vendored=true

src/frontend/terminaloverlay.cc

@@ -37,6 +37,7 @@
 #include <typeinfo>
 
 #include "src/frontend/terminaloverlay.h"
+#include "src/util/char_utils.h"
 
 using namespace Overlay;
 
@@ -257,7 +258,7 @@ void NotificationEngine::apply( Framebuffer& fb ) const
     }
 
     wchar_t ch = *i;
-    int chwidth = ch == L'\0' ? -1 : wcwidth( ch );
+    int chwidth = ch == L'\0' ? -1 : mosh_wcwidth( ch );
     Cell* this_cell = 0;
 
     switch ( chwidth ) {
@@ -709,7 +710,7 @@ void PredictionEngine::new_user_byte( char the_byte, const Framebuffer& fb )
             }
           }
         }
-      } else if ( ( ch < 0x20 ) || ( wcwidth( ch ) != 1 ) ) {
+      } else if ( ( ch < 0x20 ) || ( mosh_wcwidth( ch ) != 1 ) ) {
         /* unknown print */
         become_tentative();
         //	fprintf( stderr, "Unknown print 0x%x\n", ch );

src/terminal/terminal.cc

@@ -38,6 +38,7 @@
 #include <unistd.h>
 
 #include "src/terminal/terminal.h"
+#include "src/util/char_utils.h"
 
 using namespace Terminal;
 
@@ -65,7 +66,7 @@ void Emulator::print( const Parser::Print* act )
    * Check for printing ISO 8859-1 first, it's a cheap way to detect
    * some common narrow characters.
    */
-  const int chwidth = ch == L'\0' ? -1 : ( Cell::isprint_iso8859_1( ch ) ? 1 : wcwidth( ch ) );
+  const int chwidth = ch == L'\0' ? -1 : ( Cell::isprint_iso8859_1( ch ) ? 1 : mosh_wcwidth( ch ) );
 
   Cell* this_cell = fb.get_mutable_cell();
 

src/util/char_utils.h

@@ -0,0 +1,34 @@
+#ifndef CHAR_UTILS_HPP
+#define CHAR_UTILS_HPP
+
+#include "widechar_width.h"
+
+static int mosh_wcwidth( uint32_t c )
+{
+  int width = widechar_wcwidth( c );
+  if ( width >= 0 ) {
+    return width;
+  }
+
+  /* https://github.com/ridiculousfish/widecharwidth/tree/master#c-usage */
+  switch ( width ) {
+    case widechar_nonprint:
+      return -1;
+    case widechar_combining:
+      return 0;
+    case widechar_ambiguous:
+      return 1;
+    case widechar_private_use:
+      return 1;
+    case widechar_unassigned:
+      return -1;
+    case widechar_non_character:
+      return -1;
+    case widechar_widened_in_9:
+      return 2;
+    default:
+      return -1;
+  }
+}
+
+#endif