Q21987: ON KEY Trap Fails If CAPS/NUM LOCK Active; Need Separate KEY

Article: Q21987
Product(s): See article
Version(s): 2.00 2.01 3.00 4.00 4.00b 4.50
Operating System(s): MS-DOS
Keyword(s): ENDUSER | B_BasicCom docerr | mspl13_basic
Last Modified: 15-JAN-1990

This article describes a necessary addition to the "Microsoft
QuickBASIC Compiler" manual for Versions 2.00, 2.01, and 3.00. This
information is already covered in the documentation for QuickBASIC
Versions 4.00, 4.00b, and 4.50, Microsoft BASIC Compiler Versions
6.00, 6.00b, and Microsoft BASIC Professional Development System (PDS)
Version 7.00. The information below also applies to these versions.

Key trapping does not function while the CAPS LOCK key or NUM LOCK key
is activated, unless you specifically set up special user-defined keys
for that key combination. The program below (and the similar program
on Page 317 of the "Microsoft QuickBASIC Compiler" manual for Versions
2.00, 2.01, and 3.00) demonstrates the ignored key trapping when CAPS
LOCK or NUM LOCK is active.

The following program correctly traps CTRL+C when CAPS LOCK and NUM
LOCK are NOT active, but does NOT trap CTRL+C if either CAPS LOCK or
NUM LOCK (or both) is activated:

   key 15,chr$(&H04)+chr$(&H2E)
   key(15) on
   on key(15) gosub test
   while x$<>chr$(27)
   x$=inkey$
   if x$<>"" the print x$,asc(x$)
   wend
   end
   test:
   print "Control-C has been trapped"
   return

This behavior is not a problem in the compiler. The following notes
should be added to Page 317 of the "Microsoft QuickBASIC Compiler"
manual for Versions 2.0x and 3.00; these notes also apply to
QuickBASIC Versions 4.00, 4.00b, and 4.50, BASIC Compiler Versions
6.00, 6.00b, and BASIC PDS Version 7.00.

To trap the desired key in combination with the CAPS LOCK or NUM LOCK
key active, a different keyboard flag must be used for each
combination. A value of &H20 hex must be added to the keyboard flag if
you want to trap a key while the NUM LOCK key is down. An &H40 must be
added to the keyboard flag if you want to trap a key while the CAPS
LOCK key is down. For example, a KEY 16 can be added to the above
program to trap CTRL+C while the CAPS LOCK key is down, as in the
following:

   KEY 16, CHR$(&H44)+CHR$(&H2E)
   ON KEY (16) GOSUB TEST

The &H44 above reflects the sum of &H40 (for CAPS LOCK active) and
&H04 (the keyboard flag for CTRL).

A KEY 17 can be added to the above program to trap CTRL+C when both
CAPS LOCK and NUM LOCK are pressed down, as in the following:

   KEY 17, CHR$(&H64)+CHR$(&H2E)
   ON KEY (17) GOSUB TEST

The keyboard flag &H64 above reflects the sum of &H40 (for CAPS LOCK
active), &H20 (for NUM LOCK active), and &H04 (the keyboard flag for
CTRL).

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