added a message color API

This enables colorful formatting of any message printed through the messaget
API.  Server-side implementation is provided for Windows and Unix consoles.

Author: kroening

src/util/cout_message.cpp

@@ -21,6 +21,8 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <io.h>
 #include <cstdio>
 #include <util/pragma_pop.def>
+#else
+#include <unistd.h>
 #endif
 
 #include "unicode.h"
@@ -35,6 +37,35 @@ cerr_message_handlert::cerr_message_handlert():
 {
 }
 
+console_message_handlert::console_message_handlert(bool _always_flush)
+  : always_flush(_always_flush), is_a_tty(false), use_SGR(false)
+{
+#ifdef _WIN32
+  HANDLE out_handle=GetStdHandle(STD_OUTPUT_HANDLE);
+
+  DWORD consoleMode;
+  if(GetConsoleMode(out_handle, &consoleMode))
+  {
+    is_a_tty = true;
+
+    consoleMode |= ENABLE_VIRTUAL_TERMINAL_PROCESSING;
+    if(SetConsoleMode(out_handle, consoleMode))
+      use_SGR = true;
+  }
+#else
+  is_a_tty = isatty(STDOUT_FILENO);
+  use_SGR = is_a_tty;
+#endif
+}
+
+std::string console_message_handlert::command(unsigned c) const
+{
+  if(!use_SGR)
+    return std::string();
+
+  return "\x1b[" + std::to_string(c) + 'm';
+}
+
 void console_message_handlert::print(
   unsigned level,
   const std::string &message)

src/util/cout_message.h

@@ -36,17 +36,18 @@ class console_message_handlert : public message_handlert
 
   virtual void flush(unsigned level) override;
 
-  console_message_handlert() : always_flush(false)
+  console_message_handlert() : console_message_handlert(false)
   {
   }
 
-  explicit console_message_handlert(bool always_flush)
-    : always_flush(always_flush)
-  {
-  }
+  explicit console_message_handlert(bool always_flush);
+
+  std::string command(unsigned c) const override;
 
 protected:
   const bool always_flush;
+  bool is_a_tty;
+  bool use_SGR;
 };
 
 class gcc_message_handlert : public message_handlert

src/util/message.h

@@ -65,6 +65,11 @@ class message_handlert
     return message_count[level];
   }
 
+  virtual std::string command(unsigned) const
+  {
+    return std::string();
+  }
+
 protected:
   unsigned verbosity;
   std::vector<std::size_t> message_count;
@@ -275,6 +280,50 @@ class messaget
     return m;
   }
 
+  std::string command(unsigned c) const
+  {
+    if(message_handler)
+      return message_handler->command(c);
+    else
+      return std::string();
+  }
+
+  // return to default
+  std::string reset() const
+  {
+    return command(0);
+  }
+
+  // set red foreground color
+  std::string red() const
+  {
+    return command(31);
+  }
+
+  // set green foreground color
+  std::string green() const
+  {
+    return command(32);
+  }
+
+  // set yellow foreground color
+  std::string yellow() const
+  {
+    return command(33);
+  }
+
+  // set blue foreground color
+  std::string blue() const
+  {
+    return command(34);
+  }
+
+  // set bold font
+  std::string bold() const
+  {
+    return command(1);
+  }
+
   mstreamt &get_mstream(unsigned message_level) const
   {
     mstream.message_level=message_level;

src/util/ui_message.h

@@ -89,6 +89,11 @@ class ui_message_handlert : public message_handlert
     const source_locationt &location);
 
   const char *level_string(unsigned level);
+
+  std::string command(unsigned c) const override
+  {
+    return message_handler->command(c);
+  }
 };
 
 #define OPT_FLUSH "(flush)"