CTFramesetterSuggestFrameSizeWithConstraints: what attributes can be set?

The documentation for CTFramesetterSuggestFrameSizeWithConstraints describes the frameAttributes parameter as so:

Additional attributes that control the frame filling process, or NULL if there are no such attributes.

I've only ever set this parameter to NULL and can't seem to find any documentation on what I can set these attributes to. The CTFramesetterCreateFrame also takes a frameAttributes parameter, but there's no documenta开发者_C百科tion there, either.

Does anyone know where the documentation for these parameters is?

That parameter is named frameAttributes, which implies that they're the same attributes that would be valid when creating a frame and that you might retrieve by asking the frame for them.

The documentation doesn't directly say what attributes a frame can have. However, it does have, in the CTFrame reference, constants named kCTFrameProgressionAttributeName, kCTFramePathFillRuleAttributeName, and kCTFramePathWidthAttributeName, along with constants for the values for the two that require constant values.

So, educated guess: Those attributes.