If FetchTaggedData isn't used that often, how do I modify such things on the fly? For instance, if the user specifies a PPD when the DTP is created, how do I notify GX of the new list of paper types? Do I have to change/add resources in the driver or DTP?
A It's true that FetchTaggedData is not called as often as you would expect. The LaserWriter GX driver does get the paper types and other resources directly from the driver. The job collection is setup when the DTP is created.
There are three things that prevent you from telling GX which fonts the user downloads to the printer's disk file in the current version of GX:
1. The font name is stored in the resource name of the 'pfnt' resource, so FetchTaggedData can't access the name.
2. The core GX printing code never looks in desktop printer files for 'pfnt's.
3. The core GX printing code doesn't use FetchTaggedData to load the other 'pfnt's, so there is no way to override the current behavior.
What you are trying to do is perfectly reasonable, and there's no reason why GX should have this limitation. A fix for these problems ought to be incorporated into a future version of GX.