Use std::invalid_argument in Utf8CharSizeAt

src/common/stringutils.cpp

@@ -184,7 +184,12 @@ int StrUtils::Utf8CharSizeAt(const std::string &str, unsigned int pos)
     if((c & 0b1111'1000) == 0b1111'0000)
         return 4;
 
-    return 1;
+    // Invalid char - unexpected continuation byte
+    if (isUtf8ContinuationByte(c))
+        throw std::invalid_argument("Unexpected UTF-8 continuation byte");
+
+    // (c & 0b1111'1000) == 0b1111'1000 is true here
+    throw std::invalid_argument("Byte value has no sense in UTF-8");
 }
 
 std::size_t StrUtils::Utf8StringLength(const std::string &str)

src/graphics/engine/text.cpp

@@ -937,7 +937,14 @@ int CText::GetCharSizeAt(Gfx::FontType font, const std::string& text, unsigned i
     }
     else
     {
-        len = StrUtils::Utf8CharSizeAt(text, index);
+        try
+        {
+            len = StrUtils::Utf8CharSizeAt(text, index);
+        }
+        catch (std::invalid_argument &e)
+        {
+            len = 1;
+        }
     }
     return len;
 }