CPSUI Message Handler
Important
The modern print platform is Windows' preferred means of communicating with printers. We recommend that you use Microsoft's IPP inbox class driver, along with Print Support Apps (PSA), to customize the print experience in Windows 10 and 11 for printer device development.
For more information, see Modern print platform and the Print support app design guide.
A CPSUI message handler is a callback function that is defined using the _CPSUICALLBACK function type. This type of page event callback is recommended if you are using CPSUI-supplied pages and templates.
When a user interacts with a property sheet page and causes an event to occur, CPSUI intercepts the event and calls the _CPSUICALLBACK-typed function, supplying a CPSUICBPARAM structure that describes the reason the callback function is being called.
The callback function must handle the event, and then return a status value to CPSUI that indicates if the page needs to be redisplayed or reinitialized.