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mov ax, 4005h       ; Save Video Register State
int 2fh
 
The Save Video Register State function notifies VM applications that the
virtual-display device (VDD) requires access to the video hardware
registers. The VDD calls this function, for example, when preparing to copy
the entire screen to the clipboard.
 
Return Value
 
This function has no return value.
 
Comments
 
The VDD calls this function only if the VM application has called Enable
VM-Assisted Save/Restore (Interrupt 2Fh Function 4000h). VM applications
that receive Save Video Register State must save any data necessary to
restore the current video state and must return within 1000ms. If the
application fails to return in time, the virtual-display device accesses the
video hardware anyway. After accessing the video hardware registers, the VDD
calls Restore Video Register State (Interrupt 2Fh Function 4006h) to notify
the application that it can restore its video state.
 
The VDD calls Save Video Register State only at times when the hardware must
be reprogrammed for what are essentially brief and nonvisible operations.
For example, the VDD does not call this function prior to calling Notify
Background Switch (Interrupt 2Fh Function 4001h).
 
 
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