Inside Macintosh: QuickDraw GX Printing Extensions and Drivers /

Chapter 4 - Printing Messages / Printing Messages Reference

Printing Messages / Device Communications Messages

GXCheckStatus

QuickDraw GX sends the GXCheckStatus message to mark a location in the communications process where a status check needs to be performed. You need to override the GXCheckStatus message to check the status of your device. Your override of the GXCheckStatus message must match the following formal declaration:

OSErr MyCheckStatus (Ptr data, long length, short statusType,
                     Signature owner);

data

A pointer to the data that you want to send with the status.

length

The number of bytes in the data.

statusType

The application-defined status type.

owner

The ID of the message handler for which the GXCheckStatus message
is intended.

function result

An error code. The value noErr indicates that the operation was successful.

DESCRIPTION

You can send the GXCheckStatus message to mark the point in the imaging-communications process where you can check status information about the device.

The default implementation of this message does nothing. You need to override this message to provide status checking for your device.

The message handler that sends the GXCheckStatus message sets the data, length, and statusType parameters. You need to check the owner parameter and only process the status check if it matches your signature; if not, you need to forward the message. Most message handlers call the GXGetDeviceStatus message in response to the GXCheckStatus message.

SPECIAL CONSIDERATIONS

You can send the GXCheckStatus message yourself to mark a place where you want to have a status check performed.

If you process the status check in your override, you do not forward the GXCheckStatus message. If you do not handle the status check, you must forward the message.

RESULT CODES

gxSegmentLoadFailedErr	A required code segment could not be found, or there was not enough memory to load it.
gxPrUserAbortErr	The user has canceled printing.

SEE ALSO

The GXGetDeviceStatus message is described in the next section.

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