Message handler: add quote_begin, quote_end commands

These will permit custom formatting of quoting for each message handler,
See #4875 for discussion.

Author: tautschnig

src/util/cout_message.cpp

@@ -70,6 +70,10 @@ console_message_handlert::console_message_handlert(bool _always_flush)
 /// \param c: ECMA-48 command code
 std::string console_message_handlert::command(unsigned c) const
 {
+  // quote_begin and quote_end
+  if(c == '<' || c == '>')
+    return "'";
+
   if(!use_SGR)
     return std::string();
 

src/util/message.cpp

@@ -95,6 +95,8 @@ const messaget::commandt messaget::bright_yellow(93);
 const messaget::commandt messaget::bright_blue(94);
 const messaget::commandt messaget::bright_magenta(95);
 const messaget::commandt messaget::bright_cyan(96);
+const messaget::commandt messaget::quote_begin('<');
+const messaget::commandt messaget::quote_end('>');
 
 /// Parse a (user-)provided string as a verbosity level and set it as the
 /// verbosity of dest.

src/util/message.h

@@ -390,6 +390,12 @@ class messaget
   /// render underlined text
   static const commandt underline;
 
+  /// start quoted text
+  static const commandt quote_begin;
+
+  /// start quoted text
+  static const commandt quote_end;
+
   mstreamt &get_mstream(unsigned message_level) const
   {
     mstream.message_level=message_level;

src/util/ui_message.h

@@ -96,10 +96,74 @@ class ui_message_handlert : public message_handlert
 
   std::string command(unsigned c) const override
   {
-    if(message_handler)
-      return message_handler->command(c);
-    else
+    if(!message_handler)
       return std::string();
+
+    switch(_ui)
+    {
+    case uit::PLAIN:
+      switch(c)
+      {
+      case '<': // fall through
+      case '>':
+        return "'";
+      }
+      break;
+    case uit::XML_UI:
+      switch(c)
+      {
+      case 0:  // reset
+      case 1:  // bold
+      case 2:  // faint
+      case 3:  // italic
+      case 4:  // underline
+      case 31: // red
+      case 32: // green
+      case 33: // yellow
+      case 34: // blue
+      case 35: // magenta
+      case 36: // cyan
+      case 91: // bright_red
+      case 92: // bright_green
+      case 93: // bright_yellow
+      case 94: // bright_blue
+      case 95: // bright_magenta
+      case 96: // bright_cyan
+        return std::string();
+      case '<': // quote_begin
+      case '>': // quote_end
+        return "'";
+      }
+      break;
+    case uit::JSON_UI:
+      switch(c)
+      {
+      case 0:  // reset
+      case 1:  // bold
+      case 2:  // faint
+      case 3:  // italic
+      case 4:  // underline
+      case 31: // red
+      case 32: // green
+      case 33: // yellow
+      case 34: // blue
+      case 35: // magenta
+      case 36: // cyan
+      case 91: // bright_red
+      case 92: // bright_green
+      case 93: // bright_yellow
+      case 94: // bright_blue
+      case 95: // bright_magenta
+      case 96: // bright_cyan
+        return std::string();
+      case '<': // quote_begin
+      case '>': // quote_end
+        return "'";
+      }
+      break;
+    }
+
+    return message_handler->command(c);
   }
 };