QML Key event Qt.key_Minus can't used

[neng]

I run some .qml file with qmlscene, but key event Qt.key_Plus has no effect, and when I pressed Qt.key_Minus several times, the GreenSquare became larger, Qt version: 5.6.0, OS: redhat 6/ubuntu.
Codes:
keys.qml:

import QtQuick 2.0

DarkSquare {
    width: 400; height: 200

    GreenSquare {
        id: square
        x: 8; y: 8
    }

    focus: true
    Keys.onLeftPressed: square.x -= 8
    Keys.onRightPressed: square.x += 8
    Keys.onUpPressed: square.y -= 8
    Keys.onDownPressed: square.y += 8
    Keys.onPressed: {
        switch (event.key) {
        case Qt.Key_Plus:
            square.scale += 0.2
            break;
        case Qt.Key_Minus:
            square.scale -= 0.2
            break;
        }
    }
}

DarkSquare.qml:

import QtQuick 2.0

Rectangle {
    width: 48
    height: 48
    color: "black"
    border.color: Qt.darker(color)
}

GreenSquare.qml:

import QtQuick 2.0

DarkSquare {
    width: 48
    height: 48
    color: "green"
    border.color: Qt.lighter(color)
}

What can I do to avoid this bug, or fix this bug?

[medyakovvit]

@neng
If you mean that size of rectangle increased after scale become < 0, then Item.scale

A scale of less than 1.0 causes the item to be rendered at a smaller size, and a scale greater than 1.0 renders the item at a larger size. A negative scale causes the item to be mirrored when rendered.

[neng]

Thank you for the reply!
but key event Qt.key_Plus has no effect, mybe I need to change the key instead of Qt.key_plus to enlarge the target.

[neng]

I Use Qt.key_0 to enlarge the rectangle, the rectangle is enlarged successfully, I think it's qt quick's bug.

[medyakovvit]

@neng said:

Is Keys.onPressed executed when you press "+"? And if yes, what the value of event.key?

[neng]

Thanks, it's my problem.
If you need event Qt.key_plus, you must press Shift and =, else if you press =, the event is Qt::Key_Equal.