QValidator for hex input
- by Evan Teran
I have a Qt widget which should only accept a hex string as input. It is very simple to restrict the input characters to [0-9A-Fa-f], but I would like to have it display with a delimiter between "bytes" so for example if the delimiter is a space, and the user types 0011223344 I would like the line edit to display 00 11 22 33 44 Now if the user presses the backspace key 3 times, then I want it to display 00 11 22 3.
I almost have what i want, so far there is only one subtle bug involving using the delete key to remove a delimiter. Does anyone have a better way to implement this validator? Here's my code so far:
class HexStringValidator : public QValidator {
public:
HexStringValidator(QObject * parent) : QValidator(parent) {}
public:
virtual void fixup(QString &input) const {
QString temp;
int index = 0;
// every 2 digits insert a space if they didn't explicitly type one
Q_FOREACH(QChar ch, input) {
if(std::isxdigit(ch.toAscii())) {
if(index != 0 && (index & 1) == 0) {
temp += ' ';
}
temp += ch.toUpper();
++index;
}
}
input = temp;
}
virtual State validate(QString &input, int &pos) const {
if(!input.isEmpty()) {
// TODO: can we detect if the char which was JUST deleted
// (if any was deleted) was a space? and special case this?
// as to not have the bug in this case?
const int char_pos = pos - input.left(pos).count(' ');
int chars = 0;
fixup(input);
pos = 0;
while(chars != char_pos) {
if(input[pos] != ' ') {
++chars;
}
++pos;
}
// favor the right side of a space
if(input[pos] == ' ') {
++pos;
}
}
return QValidator::Acceptable;
}
};
For now this code is functional enough, but I'd love to have it work 100% as expected. Obviously the ideal would be the just separate the display of the hex string from the actual characters stored in the QLineEdit's internal buffer but I have no idea where to start with that and I imagine is a non-trivial undertaking.
In essence, I would like to have a Validator which conforms to this regex: "[0-9A-Fa-f]( [0-9A-Fa-f])*" but I don't want the user to ever have to type a space as delimiter. Likewise, when editing what they types, the spaces should be managed implicitly.
