VioRegister

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
0	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
0	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:

  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.