Yeah, it can get confusing, it is so flexible it is rigid sometimes :)
 
In the general case, you do not need to call PdGetDevices() and PdSetTargetDevice(), because by default the library sets
 everything up for the primary display device.
 
Now, if you had two graphics cards in the machine, you could use PdGetDevices() to find the information of the graphics 
regions.  You when then call:
 
PdSetTargetDevice(NULL, target_rid_of_device_to_use);
PdCreateOffscreenContext(..................);
 
The first parameter of PdSetTargetDevice() is the 'default' draw context you want everything referenced against ... by 
default it is the draw context contained in the global _Ph_.  If you were using another draw context as your 'default', 
you would pass it in there ... but yes, from the docs it can appear that there is a circular dependency.
 
I hope this is a little more clear now.  It does not help anything that 'void *' were used in all these prototypes.
 
Kind Regards,
-Derek

________________________________

From: Mike Gorchak [mailto:community-noreply@qnx.com]
Sent: Fri 27/03/2009 4:03 AM
To: photon-graphics
Subject: PdGetDevices() and PdSetTagetDevice(): can't get what to do



PdGetDevices() returns array of rids, it's ok with this function. Clear and understandable.

a) PdSetTargetDevice() requires DC, and documentation mentions, that I can pass PdOffscreenContext_t to it, so I need to
 create it.

b) PdCreateOffscreenContext() and PdCreateOffscreenContextGF() documentation mentions, that before offscreen context 
creation I must target this function to the specific device, go to step a).

This looks a bit of recursive for me.

What to do if I have two different video cards which are handled by Photon ? As far as I understand, PdGetDevices() 
returns two rids in array. But what to do next ? How to target PdCreateOffscreenContext() or 
PdCreateOffscreenContextGF() to specific video driver, for right memory allocation. I can imaging what would be if 
memory was allocated by one driver and then was passed it to another driver :-/


_______________________________________________
Photon microGUI
http://community.qnx.com/sf/go/post25421