What does the CFDictionary passed to CGContextBeginTransparencyLayer specify?

Question

According to Apple documentation it is possible to pass CFDictionaryRef auxiliaryInfo when creating/beginning a transparency layer, but I cannot find any documentation or examples on what key-value pairs might be appropriate for this or how it might be used. Can anyone shed light on this or should it always be null?

Answer 1

The auxiliaryInfo dictionary is intended for future use to be used for layer options, however currently it is not being used in the Quartz 2D API. So for now it should always be NULL for this function.