tests on QColor in qml

[kgregory]

I have a property that is a QColor in my qt quick application. I want to use the lightness() method to test if the lightness is above or below a certain level. This method doesn't work in qml because it's a c++ class method. Can anyone recommend how to do this test in the qml section?

Image {
        id: myImage
        anchors.verticalCenter: myBox.verticalCenter
        anchors.horizontalCenter: myBox.horizontalCenter
        height: .7 * myBox.height
        width: .7 * myBox.height
        sourceSize.height: 128
        sourceSize.width: 128
        fillMode: Image.PreserveAspectFit
        source: "someImage.png"
        visible: (myClass.someColor.lightnessF() < 10)        <--- this is the problem 
    }

[6thC]

http://doc.qt.io/qt-5/qtqml-cppintegration-interactqmlfromcpp.html

[edit]

"This method doesn't work in qml because it's a c++ class method."

That's a false assertion. You can go QML to c++ and c++ to qml rather easily and it's probably the most documented area of the documentation.

[Diracsbracket]

@kgregory said in tests on QColor in qml:

visible: (myClass.someColor.lightnessF() < 10) <--- this is the problem

The QColor property you pass from C++ to QML gets automatically converted to a QML basic Color type which apparently does not have any properties other than its color value...
http://doc.qt.io/qt-5/qml-color.html

So, to get the result of lightnessF(), you will need to add your own method to your custom C++ class, e.g. like:

    Q_INVOKABLE qreal lightnessF(){return m_color.lightnessF();}

[Diracsbracket]

@6thC said in tests on QColor in qml:

That's a false assertion

It actually is not, in this case. QColor automatically gets converted to Color, and Color has no methods, it seems?. The lightnessF() method is therefore a pure C++ method, and cannot be accessed directly in QML by passing a QColor object.

[6thC]

I think I misunderstood. My comments were around the QML / Cpp integration and not on QColor - I just head you couldn't signal between qml and cpp ... nvm me, I didn't read it deeply enough it seems.

Sadly, I've been bit like this too (I think) where I use QML charts but need cpp replace() ... it's a pity they aren't 100% feature identical but I guess it is what it is hey.