qml设计中怎么实现按钮的点击效果

在官网对qml的教程中看到对于一个text在设计师中“In Bindings, create bindings to properties，Set the source property of scale as if (!mouseArea and the source item as pressed) { 1 } else { 0.95 }.”，但是这句话没法添加，怎么添加都是错误，请教大神解救，附上原文链接地址：http://doc.qt.io/qtcreator/quick-scalable-image.html

么实现按钮的点击效果
在官网对qml的教程中看到对于一个text在设计师中“In Bindings, create bindings to properties，Set the source property of scale as if (!mouseArea and the source item as presse