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Q35519: PCOPY & Multiple Pages Not Supported in MS OS/2 Protected Mode

Article: Q35519
Product(s): See article
Version(s): 6.00 6.00b 7.00
Operating System(s): OS/2
Keyword(s): ENDUSER | SR# G880910-3123 docerr | mspl13_basic
Last Modified: 2-FEB-1990

Multiple video pages are not supported in the protected mode of MS
OS/2. As stated on Page 40 of the "Microsoft BASIC Compiler 6.0:
User's Guide" and on Page 522 of the "Microsoft BASIC 7.0:
Programmer's Guide," the SCREEN function ignores the active and visual
page parameters.

Since multiple pages are not supported, the PCOPY function is not
allowed in MS OS/2 protected mode. This fact needs to be added to the
section on BASIC language changes for MS OS/2 protected mode.

Through BASIC, there is no way to manipulate the video buffer directly
in MS OS/2 protected mode. However, it can be done through the use of
OS/2 API calls. The following API calls can be used to modify the
video buffer:

   VioGetBuf
   VioShowBuf
   VioGetPhysBuf
   VioScrLock
   VioScrUnLock

The VioGetBuf function retrieves the address and length of the logical
video buffer (LVB). The address of the buffer is returned in a long.
The high 2 bytes are the segment and the low 2 bytes are the offset,
as in the following example:

   x = VioGetBuf(pointer, length, 0)
   segment& = pointer / &H10000
   offset& = pointer MOD &H10000

To modify the buffer, change the segment to the segment value returned
and use PEEK and POKE to read and modify the information. Once the
information is changed, VioShowBuf is used to display the changes.

The VioGetPhysBuf function retrieves the selector of the physical
video buffer. The physical video buffer contains the current screen
image. To modify the screen, change the segment to the selector
returned and use PEEK and POKE to read and modify the screen. This
method is faster than using VioGetBuf/VioShowBuf because you are
directly modifying the screen.

For more information about these VIO API calls, please refer to your
OS/2 documentation. Listed below are two sample programs that use the
methods discussed above.

Code Examples
-------------

'The following program uses VioGetPhysBuf:
DEFINT A-Z
TYPE PhysBufData
     bufstart AS LONG
     buflength AS LONG
     selector1 AS INTEGER
     selector2 AS INTEGER
END TYPE

DECLARE FUNCTION VioGetBuf (_
   SEG p1 AS LONG,_
   SEG p2 AS INTEGER,_
   BYVAL p3 AS INTEGER)

DECLARE FUNCTION VioShowBuf (_
   BYVAL p1 AS INTEGER,_
   BYVAL p2 AS INTEGER,_
   BYVAL p3 AS INTEGER)

DECLARE FUNCTION VioGetPhysBuf (_
   SEG p1 AS PhysBufData,_
   BYVAL p2 AS INTEGER)

DECLARE FUNCTION VioScrLock (_
   BYVAL p1 AS INTEGER,_
   SEG p2 AS INTEGER,_
   BYVAL p3 AS INTEGER)

DECLARE FUNCTION VioScrUnLock (_
   BYVAL p1 AS INTEGER)

CLS
FOR i = 1 TO 10
    PRINT "This is a test"
NEXT i
DIM stuff AS PhysBufData
x = VioScrLock(1, status, 0)
PRINT
PRINT "Lock Status: "; status
stuff.bufstart = &HB8000
stuff.buflength = 43 * 80 * 2
x = VioGetPhysBuf(stuff, 0)
IF (x) THEN
    PRINT "Error: "; x; " occurred."
    END
ELSE
    PRINT
    PRINT "Start: "; HEX$(stuff.bufstart)
    PRINT "Length: "; stuff.buflength
    PRINT "Selector1: "; stuff.selector1
    PRINT "Selector2: "; stuff.selector2
    PRINT
    PRINT
    PRINT "Enter a key to begin changing..."
    WHILE INKEY$ = "": WEND
    offset = 0
    DEF SEG = stuff.selector1
    FOR i = offset TO offset& + stuff.buflength - 1 STEP 2
       POKE i, 65     'Character
       POKE i + 1, &H17'Attribute
    NEXT i
    DEF SEG
    x = VioScrUnLock(0)
END IF
PRINT "Enter a key to quit..."
WHILE INKEY$ = "": WEND
END

'The following program uses VioGetBuf/VioShowBuf:
DEFINT A-Z
TYPE PhysBufData
     bufstart AS LONG
     buflength AS LONG
     selector1 AS INTEGER
     selector2 AS INTEGER
END TYPE

DECLARE FUNCTION VioGetBuf (_
   SEG p1 AS LONG,_
   SEG p2 AS INTEGER,_
   BYVAL p3 AS INTEGER)

DECLARE FUNCTION VioShowBuf (_
   BYVAL p1 AS INTEGER,_
   BYVAL p2 AS INTEGER,_
   BYVAL p3 AS INTEGER)

DECLARE FUNCTION VioGetPhysBuf (_
   SEG p1 AS PhysBufData,_
   BYVAL p2 AS INTEGER)

DECLARE FUNCTION VioScrLock (_
   BYVAL p1 AS INTEGER,_
   SEG p2 AS INTEGER,_
   BYVAL p3 AS INTEGER)

DECLARE FUNCTION VioScrUnLock (_
   BYVAL p1 AS INTEGER)

CLS
FOR i = 1 TO 10
    PRINT "This is a test"
NEXT i
DIM pointer AS LONG
DIM length AS INTEGER
DIM handle AS INTEGER
x = VioGetBuf(pointer, length, 0)
segment& = pointer / &H10000
offset& = pointer MOD &H10000
IF (x) THEN
    PRINT "Error: "; x; " occurred."
    END
ELSE
    PRINT "POINTER = "; HEX$(pointer)
    PRINT "LENGTH = "; length
    PRINT
    PRINT "SEGMENT = "; HEX$(segment&)
    PRINT "OFFSET = "; HEX$(offset&)
    PRINT
    PRINT "Enter a key to begin changing the buffer..."
    WHILE INKEY$ = "": WEND
    CLS
    DEF SEG = segment&
    FOR i = offset TO offset& + length - 1 STEP 2
      POKE i, 65     'Character
      POKE i + 1, &H17'Attribute
    NEXT i
    DEF SEG
    PRINT "Enter a key to see the changes..."
    WHILE INKEY$ = "": WEND
    x = VioShowBuf(0, length, 0)
END IF
PRINT "Enter a key to quit..."
WHILE INKEY$ = "": WEND
END

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