anchors.fill: parent doesn't work with C++ types?

Edwin Vane

I have a very simple sublass of QQuickItem following the online code samples. My custom type is like a mouse area in that it doesn't have any visible content. When I instantiate the type in QML and specifiy anchors.fill: parent the width and height are not set (Component.onCompleted debug output shows 0 for both.

How do I get the anchor property to work properly for my custom C++ type?

p3c0

@Edwin-Vane I think the problem is more with the order of execution of onCompleted handler as said here. By the time the onCompleted is executed the size is not set. To test it try fetching width and height on some button click.

MyItem {
    id: item
    anchors.fill: parent
}

Button {
    text: "Click"
    onClicked: console.log(item.width,item.height) //Should print the new size
}

Edwin Vane

@p3c0 I don't think this is related to onCompleted. I tried exactly as you suggested and still get 0 for both width and height. I even print out width() and height() from the C++ side and they too are zero. It just seems the anchor information is never set. There's clearly something a QtQuick subclass needs to do to get the anchor information but I can't find the info anywhere.

benlau

@Edwin-Vane You don't need to do anything special to make the anchor work. I have a working QQuickItem subclass and set size via "anchors.fill:parent".

quickios/ActionSheetDemo.qml at master · benlau/quickios
quickios/qiactionsheet.cpp at master · benlau/quickios

Did you checked the parent's width and height? In QML , the children can be visible even the size of parent is (0,0).

p3c0

@Edwin-Vane AFAIK there's nothing more required. TO demonstrate it consider the following simple example:
MyItem - subclass of QQuickItem

#include <QObject>
#include <QQuickItem>

class MyItem : public QQuickItem
{
    Q_OBJECT
public:
    MyItem() {}
};

Register it

#include "myitem.h"
qmlRegisterType<MyItem>("MyItem", 1, 0, "MyItem");

QQmlApplicationEngine engine;
engine.load(QUrl(QStringLiteral("qrc:/main.qml")));

Using it in main.qml

import MyItem 1.0

Window {
    visible: true
    width: 300
    height: 300

    MyItem {
        id: item
        anchors.fill: parent
        Component.onCompleted: console.log("onCompleted: ",item.width,item.height)
    }

    Button {
        text: "Click"
        onClicked: console.log(item.width,item.height)
    }
}

If you run the above code you will find that Component.onCompleted doesn't print what is expected but on button click the item's width and height are obtained correctly.
Can you post your code ?

Edwin Vane

Thanks for the feedback. I must be doing something silly somewhere. I'll try and distill my problem down to a postable code sample if I don't solve the problem in the process.