This call registers an alternate video subsystem within a session.

Syntax

VioRegister (ModuleName, EntryPoint, FunctionMask1, FunctionMask2)

Parameters

ModuleName (PSZ) - input: Address of the ASCIIZ string containing the 1-8 character file name of the subsystem. The maximum length of the ASCIIZ string is 9 bytes including the terminating byte of zero. The module must be a dynamic link library but the name supplied must not include the .DLL extension.

EntryPoint (PSZ) - input: Address of the ASCIIZ name string containing the dynamic link entry point name of the routine in the subsystem to receive control when any of the registered functions is called. The maximum length of the ASCIIZ string is 33 bytes including the terminating byte of zero.

FunctionMask1 (ULONG) - input: A bit mask where each bit identifies a video function being registered. The bit definitions are shown below. The first word pushed onto the stack contains the high-order 16 bits of the function mask, and the second word contains the low-order 16 bits.

BIT	REGISTERED FUNCTION
31	VioPrtScToggle
30	VioEndPopUp
29	VioPopUp
28	VioSavRedrawUndo
27	VioSavRedrawWait
26	VioScrUnLock
25	VioScrLock
24	VioPrtSc
23	VioGetAnsi
22	VioSetAnsi
21	VioScrollRt
20	VioScrollLf
19	VioScrollDn
18	VioScrollUp
17	VioWrtCellStr
16	VioWrtCharStrAtt
15	VioWrtCharStr
14	VioWrtTTY
13	VioWrtNCell
12	VioWrtNAttr
11	VioWrtNChar
10	VioReadCellStr
9	VioReadCharStr
8	VioShowBuf
7	VioSetMode
6	VioSetCurType
5	VioSetCurPos
4	VioGetPhysBuf
3	VioGetBuf
2	VioGetMode
1	VioGetCurType
VioGetCurPos

FunctionMask2 (ULONG) - input : A bit mask where each bit identifies a video function being registered. The bit mask has the format shown below. The first word pushed onto the stack contains the high order 16 bits of the function mask, and the second word contains the low order 16 bits. Unused bits are reserved and must be set to zero.

Bit	Description
31-9	Reserved, set to zero
8	VioSetState
7	VioGetState
6	VioSetFont
5	VioGetCp
4	VioSetCp
3	VioGetConfig
2	VioGetFont
1	VioModeUndo
VioModeWait

Return Code

;rc (USHORT) - return:Return code descriptions are:

0 NO_ERROR

349 ERROR_VIO_INVALID_MASK

403 ERROR_VIO_INVALID_ASCIIZ

426 ERROR_VIO_REGISTER

430 ERROR_VIO_ILLEGAL_DURING_POPUP

465 ERROR_VIO_DETACHED

494 ERROR_VIO_EXTENDED_SG

Remarks

An alternate video subsystem must register which video calls it handles. The default OS/2 video subsystem is the Base Video Subsystem.

When any of the registered functions are called, control is routed to EntryPoint. When this routine is entered, four additional values (5 words) are pushed onto the stack.

The first value is the index number (Word) of the routine being called. The second value is a near pointer (Word). The third value is the caller's DS register(Word). The fourth value is the return address(DWord) to the VIO router.

For example, if VioSetCurPos were a registered function, the stack would appear as if the following instruction sequence were executed if VioSetCurPos were called and control routed to EntryPoint:

PUSH WORD Row PUSH WORD Column PUSH WORD VioHandle CALL FAR VioSetCurPos PUSH WORD Index CALL NEAR Entry point in Vio router PUSH WORD Caller's DS CALL FAR Dynamic link entry point

The index numbers that correspond to the registered functions are listed below:

Index	Function
0	VioGetPhysBuf
1	VioGetBuf
2	VioShowBuf
3	VioGetCurPos
4	VioGetCurType
5	VioGetMode
6	VioSetCurPos
7	VioSetCurType
8	VioSetMode
9	VioReadCharStr
10	VioReadCellStr
11	VioWrtNChar
12	VioWrtNAttr
13	VioWrtNCell
14	VioWrtCharStr
15	VioWrtCharStrAtt
16	VioWrtCellStr
17	VioWrtTTY
18	VioScrollUp
19	VioScrollDn
20	VioScrollLf
21	VioScrollRt
22	VioSetAnsi
23	VioGetAnsi
24	VioPrtSc
25	VioScrLock
26	VioScrUnLock
27	VioSavRedrawWait
28	VioSavRedrawUndo
29	VioPopUp
30	VioEndPopUp
31	VioPrtScToggle
32	VioModeWait
33	VioModeUndo
34	VioGetFont
35	VioGetConfig
36	VioSetCp
37	VioGetCp
38	VioSetFont
39	VioGetState
40	VioSetState

When a registered function returns to the video router, the return code is interpreted as follows:

Return code = 0 : No error. Do not invoke the corresponding Base Video Subsystem routine. Return to caller with Return code = 0.

Return code = -1 : No error. Invoke the corresponding Base Video Subsystem routine. Return to caller with Return code = return code from Base Video Subsystem.

Return code = error (not 0 or -1) : Do not invoke the corresponding Base Video Subsystem routine. Return to caller with Return code = error.

When an application registers a replacement for VioPopUp within a session, the registered routine is only invoked when that session is in the foreground. If VioPopUp is issued when that session is in the background, the OS/2 default routine is invoked.

An alternate video subsystem should be designed so the routines registered do not cause any hard errors when they are invoked. Otherwise, a system lockout occurs. Code and data segments of registered routines, that might be loaded from diskette, must be preloaded.

All VIO functions within a session are serialized on a thread basis. That is, when an alternate video subsystem receives control, it can safely assume that it is not called again from the same session until the current call has completed.

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