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Inside Macintosh: 3D Graphics Programming With QuickDraw 3D /
Chapter 18 - QuickDraw 3D Pointing Device Manager / QuickDraw 3D Pointing Device Manager Reference
Application-Defined Routines /


TQ3ChannelGetMethod

You can define a function that QuickDraw 3D calls to get a channel of a controller.

typedef TQ3Status (*TQ3ChannelGetMethod) (
TQ3ControllerRef controllerRef, 
unsigned long channel, 
void *data, 
unsigned long *dataSize);
controllerRef
A reference to a controller.
channel
An index into the list of channels associated with the specified controller. This value is always greater than or equal to 0 and less than the channel count specified at the time Q3Controller_New was called.
data
On entry, a pointer to a buffer. You should put the current value of the specified controller channel into this buffer.
dataSize
On exit, the number of bytes of data written to the specified buffer.
DESCRIPTION
Your TQ3ChannelGetMethod function should return, in the buffer pointed to by the data parameter, the current value of the controller channel specified by the controllerRef and channel parameters. Your function should also return, in the dataSize parameter, the size of that data. QuickDraw 3D allocates memory for the data buffer before it calls your function and deallocates the memory after your function has returned. The maximum number of bytes that the data buffer can hold is defined by a constant:

#define kQ3ControllerSetChannelMaxDataSize      256
SPECIAL CONSIDERATIONS
You need to define a channel-getting method only if you are writing a device driver for a controller. You can, however, call Q3Controller_GetChannel at any time to invoke a controller's channel-getting method.

RESULT CODES
Your channel-getting method should return kQ3Success if it is able to return the requested information and kQ3Failure otherwise.

SEE ALSO
See the description of Q3Controller_GetChannel on page 18-18 for information on getting a controller's channels.


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© Apple Computer, Inc.
11 JUL 1996




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