(answered by Rich Kubota of Apple's Developer Support Center on 12/23/94, Reference Number 121091)
Q1. I've just read the Display Manager chapter in the draft Inside Mac-Advanced Color Imaging book on the December '94 Developer CD. Pages 1-39 and 1-45 say that to check or set the display "mode" I should "supply the slot resource reference number returned by the Slot Manager function SGetSRsrc." Does this mean spBlock.spID?
A1. Yes, provided there is a Slot Manager. However, the Display Manager chapter doesn't explain what to do when the PCI-based systems come about next year and there is no Slot Manager. For example on the test unit that we are fortunate to have, there is no slot 0 even though there is on-board video. The Display Manager documentation is due for a revision, with an alpha draft sometime in the next couple of months. Watch for it on a coming Developer CD.
Q2. When I get an sResource for an inactive mode, how do I figure out what its device (i.e. GDHandle) is? I need to supply a device when I call DMCheckDisplayMode or DMSetDisplayMode. Figuring it out via the slot number would be easy, but unsafe since there can be multiple video devices at one slot (especially slot 0). After scratching my head, the method I came up with is to use SNextTypeSRsrc to find the active mode with the same spSlot and spDrvrHW, get its (nonzero) spRefNum, and then search the list of active graphics devices until I find one for which (**device).gdRefNum==spBlock.spRefNum. Will that work, or is there a better way?
A2. When I looked at the first part of the question, the solution which you came up with is that one that came to mind. I'm checking with the Display Manager engineer.
Q3. How do I find out what is the current display mode? I.e. how do I write my own "DMGetDisplayMode"? (I need to save the current "display mode" to restore it later, when I'm done.)
A3. --no answer yet--
Typos in the "Display Manager" chapter:
page 1-37 "DESCRIPTION In the displayID parameter, the DMGetDisplayIDByGDevice [function] returns a pointer ...".
page 1-41 "SEE ALSO ... display mode reported [on] by DMCheckDisplayMode, system software [uses] DMSetDisplayMode ..."
