struct TrimConvert : public Convert {
	virtual Value Scan(const Value& text) const {
		return TrimBoth(text.ToString());
    }
}; 

file EditCtrl.h:

class EditString : public EditValue<WString, ConvertString> {
[...]
	EditString& TrimSpaces(bool ts = true)           { ConvertString::TrimSpaces(ts); return *this; }
};



file Convert.h:

class ConvertString : public Convert {
[...]
	ConvertString& TrimSpaces(bool b = true)       { trim_spaces = b;  return *this; }
[...]
#ifdef flagSO
	ConvertString(int maxlen = INT_MAX, bool notnull = false, bool trim_spaces = false);
	virtual ~ConvertString();
#else
	ConvertString(int maxlen = INT_MAX, bool notnull = false, bool trim_spaces = false)
		: maxlen(maxlen), notnull(notnull), trim_spaces(trim_spaces) {}
#endif
[...]



file Convert.cpp:

Value ConvertString::Scan(const Value& text) const {
	if(IsError(text)) return text;
	if(IsNull(text)) return notnull ? NotNullError() : Value(text);
	if(text.GetType() == STRING_V && String(text).GetLength() <= maxlen ||
	   text.GetType() == WSTRING_V && WString(text).GetLength() <= maxlen) return trim_spaces ? Value(TrimBoth(text)) : text;
	return ErrorValue(UPP::Format(t_("Please enter no more than %d characters."), maxlen));
}



CtrlLib.usc:

ctrl EditString {
	>EditNotNull;
	bool TrimSpaces;
	raw MaxLen;

	PaintData(w) {
		text = (.NotNull ? "!" : "") + "Str";
		if(.MaxLen != "")
			text << " < " << .MaxLen;
		PaintText(w, text);
	}
}