TextField Validation of Time Input in QML - regex

Question

I am having a TextField which allows the user to enter time and I have used RegValidator to validate. Currently, I need to fill the particular position with "0" as soon as the user clicks on backspace. Following is the code:
TextField {
id:textField
text:"11:11:11"
width:200
height:80
font.pointSize: 15
color:"white"
inputMask: "99:99:99"
validator: RegExpValidator { regExp: /^([0-1\s]?[0-9\s]|2[0-3\s]):([0-5\s][0-9\s]):([0-5\s][0-9\s])$ / }
horizontalAlignment: Text.AlignHCenter
verticalAlignment: Text.AlignVCenter
inputMethodHints: Qt.ImhDigitsOnly
}

Answer 1

when user clicks on backspace
you mean just hitting the backspace key? Then it would be something like this :
TextField {
..
Keys.onBackPressed: text = "00:00:00"
}
EDIT
in order to reset just one of the numbers where the cursor is, you could do something like the following. I did not test it and maybe some of the indices are wrong, but you get the idea
TextField {
..
Keys.onBackPressed: {
var index = cursorPosition
var char = text.charAt(index)
if(char != ":"){
text = text.substr(0, index) + "0"+ text.substr(index);
}
}
}
http://doc.qt.io/qt-5/qml-qtquick-controls-textfield.html#cursorPosition-prop

Answer 2

In practice you can use displayText porperty of TextInput, like this:
TextInput {
id: textInput
inputMask: "00:00:00;0"
onDisplayTextChanged: {
// when user backspacing or deleting some character,
// this property become as visible value: "03:01:35"
// but text property has value: "03:1:35"
console.log(displayText);
}
}