color: Add the ability to selectively preserve colors

This adds back the "DECOLOR" functionality that was removed as part of Unvanquished/Unvanquished@d61c9d2.
No motivation was given for the removal, and the DECOLOR functionality
is important for external tools that parse game logs to display player
colors leading to a richer experience.

src/common/Color.cpp

@@ -86,9 +86,30 @@ int StrlenNocolor( const char *string )
 
 void StripColors( const char *in, char *out, size_t len )
 {
+	bool preserveColor = false;
+
 	for ( const auto& token : Parser( in ) )
 	{
-		Str::StringView text = token.PlainText();
+		if ( token.Type() == Token::TokenType::CONTROL )
+		{
+			if ( token.RawToken().size() != 1 )
+			{
+				Log::Warn( "Invalid control token of length %d", token.RawToken().size() );
+				continue;
+			}
+			switch ( token.RawToken()[0] )
+			{
+				case Constants::DECOLOR_ON:
+					preserveColor = false;
+					break;
+				case Constants::DECOLOR_OFF:
+					preserveColor = true;
+					break;
+			}
+			continue;
+		}
+		Str::StringView text = ( preserveColor && token.Type() == Token::TokenType::COLOR ) ?
+			token.RawToken() : token.PlainText();
 		if ( text.size() >= len )
 		{
 			break;
@@ -106,9 +127,30 @@ std::string StripColors( Str::StringRef input )
 	std::string output;
 	output.reserve( input.size() );
 
+	bool preserveColor = false;
+
 	for ( const auto& token : Parser( input.c_str() ) )
 	{
-		Str::StringView text = token.PlainText();
+		if ( token.Type() == Token::TokenType::CONTROL )
+		{
+			if ( token.RawToken().size() != 1 )
+			{
+				Log::Warn( "Invalid control token of length %d", token.RawToken().size() );
+				continue;
+			}
+			switch ( token.RawToken()[0] )
+			{
+				case Constants::DECOLOR_ON:
+					preserveColor = false;
+					break;
+				case Constants::DECOLOR_OFF:
+					preserveColor = true;
+					break;
+			}
+			continue;
+		}
+		Str::StringView text = ( preserveColor && token.Type() == Token::TokenType::COLOR ) ?
+			token.RawToken() : token.PlainText();
 		output.append( text.begin(), text.end() );
 	}
 
@@ -210,6 +252,10 @@ TokenIterator::value_type TokenIterator::NextToken(const char* input)
             }
         }
     }
+	else if ( input[0] == Constants::DECOLOR_ON || input[0] == Constants::DECOLOR_OFF )
+	{
+		return value_type( input, input + 1, value_type::TokenType::CONTROL );
+	}
 
     return value_type( input, input + Q_UTF8_Width( input ), value_type::TokenType::CHARACTER );
 }

src/common/Color.h

@@ -344,6 +344,9 @@ namespace Constants {
 enum {
 	ESCAPE = '^',
 	NULL_COLOR = '*',
+	// Magic chars to preserve colors between DECOLOR_OFF and DECOLOR_ON when calling StripColors.
+	DECOLOR_OFF = '\16',
+	DECOLOR_ON  = '\17',
 }; // enum
 } // namespace Constants
 
@@ -371,6 +374,7 @@ class Token
 		CHARACTER,     // A character
 		ESCAPE,        // Color escape
 		COLOR,         // Color code
+		CONTROL,       // Control character (basically controlling decolor behavior.)
 	};
 
 	/*

src/common/ColorTest.cpp

@@ -42,6 +42,11 @@ TEST(StripColorTest, ReturningString)
 
    std::string onlyColors = "^xF1A^1^0^O^9^a^;^*^xeE2^#123Aa5^#3903ff";
    EXPECT_EQ("", StripColors(onlyColors));
+
+    // Decolor
+    std::string decolor = Str::Format("%c^1wtf^#aabbccbad%c^1a^2c^^^3c", Constants::DECOLOR_ON, Constants::DECOLOR_OFF);
+    EXPECT_EQ("wtfbad^1a^2c^^3c", StripColors(decolor));
+
 }
 
 TEST(StripColorTest, ToBuffer)
@@ -57,8 +62,13 @@ TEST(StripColorTest, ToBuffer)
     char justright[7];
     StripColors("dretc^#123456h", justright, sizeof(justright));
     EXPECT_EQ("dretch", std::string(justright));
+
+    // Decolor
+    char decolorjustright[9];
+    StripColors(Str::Format("%c^1dretc%c^#123456h", Constants::DECOLOR_OFF, Constants::DECOLOR_ON).c_str(), decolorjustright, sizeof(decolorjustright));
+    EXPECT_EQ("^1dretch", std::string(decolorjustright));
+
 }
 
 } // namespace
 } // namespace Color
-