Simplify character test in UiValidPlayerName

Source/DiabloUI/diabloui.cpp

@@ -634,12 +634,10 @@ bool UiValidPlayerName(string_view name)
 	if (name.find_first_of(",<>%&\\\"?*#/: ") != name.npos)
 		return false;
 
-	constexpr auto isAsciiControlCharacter = [](char character) -> bool {
-		return (character >= 0x00 && character < 0x20) || character == 0x7F;
-	};
-	for (char letter : name)
-		if (isAsciiControlCharacter(letter) || !IsLeadUtf8CodeUnit(letter))
-			return false;
+	// Only basic latin alphabet is supported for multiplayer characters to avoid rendering issues for players who do
+	// not have fonts.mpq installed
+	if (!std::all_of(name.begin(), name.end(), IsBasicLatin))
+		return false;
 
 	string_view bannedNames[] = {
 		"gvdl",

Source/utils/utf8.hpp

@@ -43,6 +43,16 @@ constexpr bool IsLeadUtf8CodeUnit(char x)
 	return (x >= '\x00' && x <= '\x7F') || (x >= '\xC2' && x <= '\xF4');
 }
 
+/**
+ * Returns true if the character is part of the Basic Latin set.
+ *
+ * This includes ASCII punctuation, symbols, math operators, digits, and both uppercase/lowercase latin alphabets
+ */
+constexpr bool IsBasicLatin(char x)
+{
+	return x >= '\x20' && x <= '\x7E';
+}
+
 /**
  * Returns true if this is a trailing byte in a UTF-8 code point encoding.
  *

test/utf8_test.cpp

@@ -67,5 +67,22 @@ TEST(Utf8CodeUnits, InvalidCodePoints)
 	}
 }
 
+TEST(Utf8CodeUnits, BasicLatin)
+{
+	for (char x = '\x00'; x < '\x20'; x++) {
+		EXPECT_FALSE(IsBasicLatin(x)) << "ASCII Control characters are not Basic Latin symbols";
+	}
+
+	for (char x = '\x20'; x <= '\x7E'; x++) {
+		EXPECT_TRUE(IsBasicLatin(x)) << "Basic Latin symbols are denoted by the range 0x20 to 0x7E inclusive";
+	}
+
+	EXPECT_FALSE(IsBasicLatin('\x7F')) << "ASCII Control character DEL is not a Basic Latin symbol";
+
+	for (char x = '\x80'; x >= '\x80' && x <= '\xFF'; x++) {
+		EXPECT_FALSE(IsBasicLatin(x)) << "Multibyte Utf8 code units are not Basic Latin symbols";
+	}
+}
+
 } // namespace
 } // namespace devilution