Important Notice

The pages on this site contain documentation for very old MS-DOS software, purely for historical purposes. If you're looking for up-to-date documentation, particularly for programming, you should not rely on the information found here, as it will be woefully out of date.

                                                     ◄Up► ◄Next► ◄Previous►
────────────────────────────────────────────────────────────────────────────
 
include vdd.inc
 
VxDcall VDD_Clear_Mod
 
The VDD_Clear_Mod service clears the change state of a virtual machine.
 
Parameter   Description
────────────────────────────────────────────────────────────────────────────
 
EDX         Specifies the system virtual machine handle.
 
EBX         Specifies the handle of the virtual machine to clear the change
            state for.
 
EDI         Specifies the VDD control block pointer.
 
EBP         Points to the Client_Reg_Struc structure for the virtual
            machine.
 
Client_EBX  Specifies the virtual machine handle.
 
Return Value
 
The carry flag is set if an invalid virtual machine handle is specified.
Otherwise, this service has no return value.
 
Comments
 
This service allows proper text scrolling if an application runs between
calls to the VDD_Get_Mod and VDD_Clear_Mod services.
 
This service assumes that VDD_Clear_Mod is called twice when the VDD sends a
scroll event to 386 enhanced mode grabber; once in the TextScroll function
and again in the UpdateScreen function.
 
If an application has accessed pages since the last call to the VDD_Get_Mod
service and there is a scroll event generated in the previous VDD_Get_Mod,
the service sets the fVDD_UpdAll1Bit value in VDD_Flags and transfers main
memory to copy memory. The VDD_Clear_Mod service clears the fVDD_UpdAll1Bit
value and sets fVDD_UpdAll2Bit. The VDD_State_Query service returns changes
if fVDD_UpdAll2Bit is set. Since fVDD_UpdAll2Bit is set, the VDD_Mod_Text
service returns the entire screen changed (no scrolls) and the
VDD_Clear_Mod service clears the fVDD_UpdAll2Bit value and updates the copy
memory.
 
If application accessed pages since the last VDD_Get_Mod and there was no
scroll event in the previous VDD_Get_Mod, the copy memory is not updated.
 
Uses
 
Flags
 
                                      ♦