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         BIT   REGISTERED FUNCTION

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

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

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.