c++ - 属性QtObject marginHints:QtObject {…}

Question

查看KDE等离体的来源，一些小部件声明了marginHints属性，例如this:

    property QtObject marginHints: QtObject {
        property int left: Math.round(units.smallSpacing / 2)
        property int top: Math.round(units.smallSpacing / 2)
        property int right: Math.round(units.smallSpacing / 2)
        property int bottom: Math.round(units.smallSpacing / 2)
    }

尽管没有从任何地方明确引用，但删除它们实际上会破坏布局。

甚至在其他地方也有记载吗？如何运作？这是某种QML魔术吗？

Answer 1

看起来，QML具有比我想象的复杂得多的范围解析。不过，阅读文档(又称RTFM)会有所帮助。

https://doc.qt.io/qt-5/qtqml-documents-scope.html

根据该文章:

Component Scope

Each QML component in a QML document defines a logical scope. Each document has at least one root component, but can also have other inline sub-components. The component scope is the union of the object ids within the component and the component's root object's properties.

[...]

Component Instance Hierarchy

In QML, component instances connect their component scopes together to form a scope hierarchy. Component instances can directly access the component scopes of their ancestors.

将范围合并在一起，该项目的任何子组件的任何内部组件都可能使用过它。