This call requests ownership of (locks) the physical display buffer.
VioScrLock
WaitFlag (USHORT) - input
Value
Value
Status is returned only when AX = 0.
Status = 1 may be returned only when WaitFlag = 0.
This function call permits a process to determine if I/O to the physical screen buffer can take place. This prevents the process from writing to the physical buffer when the process is in the background. Processes must cooperate with the system in coordinating screen accesses.
Screen switching is disabled while the screen lock is in place. If a screen switch is suspended by a screen lock, and if the application holding the lock does not issue VioScrUnLock within a system-defined time limit, the screen switch occurs, and the process holding the lock is frozen in the background. A process should yield the screen lock as soon as possible to avoid being frozen when running in the background. The timeout on the lock does not begin until a screen switch is requested.
When the screen lock is in effect and another thread in the same or different process (in the same session) issues VioScrLock, the second thread receives an error code. VioScrUnLock must be issued by a thread within the same process that issued VioScrLock.
Family API Considerations
Some options operate differently in the DOS mode than in the OS/2 mode. Therefore, the following restriction applies to VioScrLock when coding in the DOS mode:
The status always indicates the lock is successful (Return code = 0).