a value with width and height attributes

The size type refers to a value with has width and height attributes.

For example, to read the width and height values of the Image::sourceSize size-type property:

Column {
    Image { id: image; source: "logo.png" }
    Text { text: image.sourceSize.width + "," + image.sourceSize.height }
}

To create a size value, specify it as a "width x height" string:

Image { sourceSize: "150x50" }

Or use the Qt.size() function:

Image { sourceSize: Qt.size(150, 50) }

When integrating with C++, note that any QSize or QSizeF value passed into QML from C++ is automatically converted into a size value, and vice-versa. When a size value is passed to C++, it is automatically converted into a QSizeF value.