3 files changed, 57 insertions, 10 deletions

diff --git a/fluid/io/Code_Writer.cxx b/fluid/io/Code_Writer.cxx
index 086244035..8bcef2f33 100644
--- a/fluid/io/Code_Writer.cxx
+++ b/fluid/io/Code_Writer.cxx
@@ -27,6 +27,11 @@
 
 #include <zlib.h>
 
+#include <string>
+#include <iomanip>
+#include <iostream>
+#include <sstream>
+
 using namespace fld;
 using namespace fld::io;
 using namespace fld::proj;
@@ -624,15 +629,51 @@ int Code_Writer::write_code(const char *s, const char *t, bool to_codeview) {
 // generated by Fast Light User Interface Designer (fluid) version %.4f\n\n";
   fprintf(header_file, hdr, FL_VERSION);
   crc_printf(hdr, FL_VERSION);
-
-  {char define_name[102];
-  const char* a = fl_filename_name(t);
-  char* b = define_name;
-  if (!isalpha(*a)) {*b++ = '_';}
-  while (*a) {*b++ = isalnum(*a) ? *a : '_'; a++;}
-  *b = 0;
-  fprintf(header_file, "#ifndef %s\n", define_name);
-  fprintf(header_file, "#define %s\n", define_name);
+  {
+    // Creating the include guard is more involved than it seems at first glance.
+    // The include guard is deduced from header filename. However, if the
+    // filename contains unicode characters, they need to be encoded using
+    // \Uxxxxxxxx or \\uxxxx encoding to form a valid macro identifier.
+    //
+    // But that approach is not portable. Windows does not normalize Unicode
+    // (ö is the letter \u00F6). macOS normalizes to NFD (ö is \u006F\u0308,
+    // o followed by a Combining Diaresis ¨).
+    //
+    // To make the include guard consistent across l=platforms, it can be
+    // explicitly set by the user in the Project Settings.
+    std::string macro_name_str = proj_.include_guard;
+    if (macro_name_str.empty()) {
+      std::ostringstream macro_name;
+      std::string header_name;
+      const char* a = nullptr;
+      if (write_codeview) {
+        header_name = proj_.headerfile_name();
+        a = header_name.c_str();
+      } else {
+        a = fl_filename_name(t);
+      }
+      const char* b = a + strlen(a);
+      int len = 0;
+      unsigned ucs = fl_utf8decode(a, b, &len);
+      if ((ucs > 127) || (!isalpha(ucs) && (ucs != '_')))
+        macro_name << '_';
+      while (a < b) {
+        ucs = fl_utf8decode(a, b, &len);
+        if ((ucs == '.') || (ucs == '_')) {
+          macro_name << '_';
+        } else if (ucs > 0x0000ffff) { // large unicode character
+          macro_name << "\\U" << std::setw(8) << std::setfill('0') << std::hex << ucs;
+        } else if ((ucs > 127) || !isalnum(ucs)) { // small unicode character or not an ASCI letter or digit
+          macro_name << "\\u" << std::setw(4) << std::setfill('0') << std::hex << ucs;
+        } else {
+          macro_name << (char)ucs;
+        }
+        a += len;
+      }
+      macro_name_str = macro_name.str();
+    }
+    fprintf(header_file, "#ifndef %s\n", macro_name_str.c_str());
+    fprintf(header_file, "#define %s\n", macro_name_str.c_str());
   }
 
   if (proj_.avoid_early_includes==0) {
diff --git a/fluid/io/Project_Reader.cxx b/fluid/io/Project_Reader.cxx
index c420824aa..0e2809685 100644
--- a/fluid/io/Project_Reader.cxx
+++ b/fluid/io/Project_Reader.cxx
@@ -277,6 +277,11 @@ Node *Project_Reader::read_children(Node *p, int merge, Strategy strategy, char
         goto CONTINUE;
       }
 
+      if (!strcmp(c,"include_guard")) {
+        proj_.include_guard = read_word();
+        goto CONTINUE;
+      }
+
       if (!strcmp(c, "snap")) {
         Fluid.layout_list.read(this);
         goto CONTINUE;
diff --git a/fluid/io/Project_Writer.cxx b/fluid/io/Project_Writer.cxx
index 1975ef85d..387c0093f 100644
--- a/fluid/io/Project_Writer.cxx
+++ b/fluid/io/Project_Writer.cxx
@@ -115,12 +115,13 @@ int Project_Writer::write_project(const char *filename, int selected_only, bool
     write_string("\nutf8_in_src");
   if (proj_.avoid_early_includes)
     write_string("\navoid_early_includes");
-    
+
   proj_.i18n.write(*this);
 
   if (!selected_only) {
     write_string("\nheader_name"); write_word(proj_.header_file_name.c_str());
     write_string("\ncode_name"); write_word(proj_.code_file_name.c_str());
+    write_string("\ninclude_guard"); write_word(proj_.include_guard.c_str());
     Fluid.layout_list.write(this);
     if (g_shell_config)
       g_shell_config->write(this);