Q63956: How to Scroll Text in BASIC Protected Mode Program Using API
Article: Q63956
Product(s): See article
Version(s): 6.00 6.00b 7.00 7.10
Operating System(s): OS/2
Keyword(s): ENDUSER | SR# S900710-57 | mspl13_basic
Last Modified: 17-JAN-1991
This article describes how protected mode BASIC programs compiled with
Microsoft BASIC Compiler versions 6.00 and 6.00b or Microsoft BASIC
Professional Development System (PDS) version 7.00 or 7.10 can scroll
text on the screen by calling the OS/2 API functions VioScrollUp(),
VioScrollDn(), VioScrollLf(), and VioScrollRt(). A full example of
using these routines is provided below.
This information applies to Microsoft BASIC Compiler versions 6.00 and
6.00b for MS OS/2 and to Microsoft BASIC Professional Development
System (PDS) versions 7.00 and 7.10 for MS OS/2.
BASIC 6.00 and 6.00b and BASIC PDS 7.00 and 7.10 can directly call
OS/2 API functions by linking with the appropriate library. This
library is called DOSCALLS.LIB for BASIC 6.00 and 6.00b and OS2.LIB
for BASIC PDS 7.00 and 7.10.
The API functions VioScrollUp(), VioScrollDn(), VioScrollLf(), and
VioScrollRt() all require the following parameters:
Parameter Description
--------- -----------
WORD y (row) coordinate of upper left corner
WORD x (column) coordinate of upper left corner
WORD y (row) coordinate of lower right corner
WORD x (column) coordinate of lower right corner
WORD Number of lines or columns to scroll
PTR WORD Contains character (lower byte) and attribute
(upper byte) used to fill blanked lines or columns
WORD Video handle (0 = default)
The first four parameters specify the rectangle in which the scrolling
is to take place. Any area outside this rectangle is not scrolled. The
sixth parameter specifies the character and attribute to use for the
new lines or columns created behind the scrolling text. Note that a
WORD in BASIC is an INTEGER, and any parameters preceded by the word
"PTR" must be passed using the SEG clause in the DECLARE statement;
BYVAL is used otherwise. The default for BASIC is to pass by reference
(not BYVAL).
The following program (SCROLL.BAS) displays a message on the screen
and allows you to scroll the message up, down, left, or right using
the cursor keys. Note that this example uses only the cursor keys on
the numeric keypad, not the extended cursor keys. Any part of the
message that is scrolled off the screen is lost. Press the ESC key to
terminate execution.
To compile and link the program, enter the following lines at the OS/2
command prompt:
bc scroll /v ;
link scroll;
Code Example
------------
'SCROLL.BAS
DEFINT A-Z
'Declarations for OS/2's Vio scroll functions.
DECLARE FUNCTION VioScrollUp (BYVAL Y1 AS INTEGER,_
BYVAL X1 AS INTEGER,_
BYVAL Y2 AS INTEGER,_
BYVAL X2 AS INTEGER,_
BYVAL Lines AS INTEGER,_
SEG FillNew AS INTEGER,_
BYVAL Handle AS INTEGER)
DECLARE FUNCTION VioScrollLf (BYVAL Y1 AS INTEGER,_
BYVAL X1 AS INTEGER,_
BYVAL Y2 AS INTEGER,_
BYVAL X2 AS INTEGER,_
BYVAL Lines AS INTEGER,_
SEG FillNew AS INTEGER,_
BYVAL Handle AS INTEGER)
DECLARE FUNCTION VioScrollRt (BYVAL Y1 AS INTEGER,_
BYVAL X1 AS INTEGER,_
BYVAL Y2 AS INTEGER,_
BYVAL X2 AS INTEGER,_
BYVAL Lines AS INTEGER,_
SEG FillNew AS INTEGER,_
BYVAL Handle AS INTEGER)
DECLARE FUNCTION VioScrollDn (BYVAL Y1 AS INTEGER,_
BYVAL X1 AS INTEGER,_
BYVAL Y2 AS INTEGER,_
BYVAL X2 AS INTEGER,_
BYVAL Lines AS INTEGER,_
SEG FillNew AS INTEGER,_
BYVAL Handle AS INTEGER)
Y1 = 0 'Set the coordinates of the window scrolling area to define
X1 = 0 'the whole screen (assuming 25 rows and 80 columns).
Y2 = 24
X2 = 79
Lines = 1 'Scroll one line at a time.
FillNew = 20010 'Fill the new lines/columns with yellow asterisks
'on a red background.
Handle = 0 'Specifies the default OS/2 screen group.
CLS 'Clear screen and display the message to scroll.
LOCATE 12, 30
PRINT "Use arrows on numeric keypad to scroll."
PRINT "Hit Esc to quit."
ON KEY(11) GOSUB UpArrow 'Setup event handlers for key trapping.
ON KEY(12) GOSUB LeftArrow 'Keys 11-14 are the arrow keys on the
ON KEY(13) GOSUB RightArrow 'numeric keypad.
ON KEY(14) GOSUB DownArrow
KEY(11) ON 'Turn key trapping on.
KEY(12) ON
KEY(13) ON
KEY(14) ON
DO UNTIL INKEY$ = CHR$(27) 'Loop until the ESC key is pressed.
LOOP
END
'Event handlers for key traps.
UpArrow: E = VioScrollUp (Y1, X1, Y2, X2, Lines, FillNew, Handle)
RETURN
LeftArrow: E = VioScrollLf (Y1, X1, Y2, X2, Lines, FillNew, Handle)
RETURN
RightArrow: E = VioScrollRt (Y1, X1, Y2, X2, Lines, FillNew, Handle)
RETURN
DownArrow: E = VioScrollDn (Y1, X1, Y2, X2, Lines, FillNew, Handle)
RETURN
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