QML Screen Coordinates of Component

Question

If I have a simple, self-contained QML application, I can get the absolute screen coordinates of a component by saying

Component.onCompeted: {    
    var l = myThing.mapToItem(null, 0, 0)
    console.log("X: " + l.x + " y: " + l.y)
}

where myThing is the id of any other component in the file. However, if this file gets incorporated into another QML file and the component it defines is reused, I don't get the screen coordinates anymore; I get the local coordinates relative to the component where the statements above are executed.

How can I get the absolute screen coordinates of items?

Answer 1

Component.onCompleted: {
    var globalCoordinares = myThing.mapToItem(myThing.parent, 0, 0)
    console.log("X: " + globalCoordinares.x + " y: " + globalCoordinares.y)
}

where myThing.parent is your main compontent.

Answer 2

Since Qt 5.7, there is Item.mapToGlobal:

Component.onCompleted: {
    var globalCoordinates = mapToGlobal(0, 0)
    console.log("X: " + globalCoordinates.x + " y: " + globalCoordinates.y)
}

Answer 3

Here is a quick and very dirty solution. Note: This has only been lightly tested but so far seems to work. I would not recommend using this in production applications as it's a complete hack and likely to break at some point.

ApplicationWindow {
    id: mainWindow
    visible: true
    width: 640
    height: 480
    x: 150.0
    y: 150.0
    title: qsTr("Hello World")

    Rectangle {
        id: lolRect
        height: 50
        width: 50
        anchors.centerIn: parent;

        Component.onCompleted: {

            function getGlobalCordinatesOfItem(item) {

                // Find the root QML Window.
                function getRootWindowForItem(item) {
                    var cItem = item.parent;
                    if (cItem) {
                        return getRootWindowForItem(cItem);
                    } else {

                        // Path to the root items ApplicationWindow
                        var rootWindow = item.data[0].target;
                        if (rootWindow && rootWindow.toString().indexOf("ApplicationWindow") !== -1) {
                            return rootWindow;
                        } else {
                            console.exception("Unable to find root window!");
                            return null;
                        }
                    }
                }

                // Calculate the items position.
                var rootWindow = getRootWindowForItem(item);
                if (rootWindow) {
                    return Qt.point(rootWindow.x + lolRect.x,
                                    rootWindow.y + lolRect.y);
                } else {
                    return null;
                }
            }

            // Print the result.
            console.log(getGlobalCordinatesOfItem(this));
        }
    }
}