The WinCPICSetBlockingHook function allows a Windows CPI-C implementation to block CPI-C function calls by means of a new function. This call is used by Microsoft® Windows® version 3.x applications to make blocking calls without blocking the rest of the system. By default in the Microsoft® Windows NT® and Windows 95 systems, blocking calls suspend the calling application's thread until the request is finished. Therefore, if a single-threaded application is targeted at both the Windows version 3.x system and the Windows NT and Windows 95 systems, and relies on this functionality, it should register a blocking hook even if the default hook will suffice.
FARPROC WINAPI WinCPICSetBlockingHook(
| FARPROC lpBlockFunc | |
| ); |
The return value points to the procedure instance of the previously installed blocking function. The application or library that calls WinCPICSetBlockingHook should save this return value so that it can be restored if needed. (If nesting is not important, the application can simply discard the value returned by WinCPICSetBlockingHook and eventually use WinCPICUnhookBlockingHook to restore the default mechanism.)
A Windows CPI-C implementation has a default mechanism by which blocking CPI-C functions are implemented. This function gives the application the ability to execute its own function at blocking time in place of the default function.
The default blocking function is equivalent to:
BOOL DefaultBlockingHook (void) {
MSG msg;
/* get the next message if any */
if ( PeekMessage (&msg,0,0,PM_NOREMOVE) ) {
if ( msg.message = = WM_QUIT )
return FALSE; // let app process WM_QUIT
PeekMessage (&msg,0,0,PM_REMOVE) ;
TranslateMessage (&msg) ;
DispatchMessage (&msg) ;
}
/* TRUE if no WM_QUIT received */
return TRUE;
}
The WinCPICSetBlockingHook function is provided to support applications that require more complex message processing—for example, those employing the multiple document interface (MDI) model or applications with Menu accelerators (TranslateAccelerator).
Blocking functions must return FALSE in response to a WM_QUIT message so Windows CPI-C can return control to the application to process the message and terminate gracefully. Otherwise, the function should return TRUE.
Set_Processing_Mode, Specify_Windows_Handle