Adding callbacks
Common Printing uses the callback mechanism to inform applications of events related to the printing process. Callbacks are added to a shell using the addCallback:receiver:selector:clientData: method. 
CwPrinterShell uses the following callbacks: 
mapCallback 
The shell has been mapped and is ready for print job production. 
exposeCallback 
The shell is ready to receive data for the current printer page. 
resizeCallback 
The shell's dimensions have been modified. 
destroyCallback 
The shell is about to be destroyed. 
The following diagram shows the proper sequencing of printer shell job commands and callbacks. 

Last modified date: 12/21/2017