A Boolean indicating whether the layer is allowed to composite itself as a group separate from its parent.
When the value is YES and the layer’s opacity property value is less than 1.0, the layer is allowed to composite itself as a group separate from its parent. This gives correct results when the layer contains multiple opaque components, but may reduce performance.
The default value is read from the boolean UIViewGroupOpacity property in the main bundle’s Info.plist file. If no value is found, the default value is YES for apps linked against the iOS 7 SDK or later and NO for apps linked against an earlier SDK.