DSETWINDOW()
 Reroutes external functions and programs to a window
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 Syntax

     DSETWINDOW([<lNewDisplayMode>]) --> lOldDisplayMode

 Argument

     <lNewDisplayMode>  Designates whether the screen output from
     external programs or other language UDF's displays in the current
     window.

 Returns

     When called without a parameter, the function returns the current
     setting for DSETWINDOW().  If a parameter is passed, it returns the
     previous setting.

 Description

     DSETWINDOW() allows you to determine if only CA-Clipper screen outputs
     should appear in a window, or if all outputs (all external modules and
     programs, including DOS) should appear.  If you would like to implement
     a subroutine for screen handling with CA-Clipper Tools window functions,
     you can use this switch to turn off these functions for a short time.

     Important!  Before you call external programs using RUN, you should
     set DSETWINDOW() to .F.; if you do not, some programs will not run
     correctly.

 Notes

     Important!  The standard setting for DSETWINDOW() is on.  This means
     that all program output, not written directly into the screen memory,
     displays in the currently active window.

     .  CA-Clipper screen output is always written in a window if one
        is open and active.  Only screen output from external routines (like
        Assembler or C UDF's, or external programs called using RUN) can be
        affected.  CA-Clipper Tools functions are also viewed as foreign or
        external.

     .  If you call DSETWINDOW() with .T., a change in cursor position
        in an external module or program also affects the cursor position in
        CA-Clipper.  If you do not want to change the cursor position in
        CA-Clipper, then set DSETWINDOW() to .F. so that the CA-Clipper
        cursor position remains unchanged.  If you still want to pass the
        cursor position to CA-Clipper, then use the SETRC() function without
        parameters.

     .  Some CA-Clipper Tools functions ignore this switch because
        they work directly with the physical screen memory.

     .  CA-Clipper Tools has a public variable available for your own
        Assembler or C routines to affect the DSETWINDOW() function.  It can
        be addressed as follows:

        EXTR _WINDOW:WORD
        MOV  _WINDOW, 0               // Window functions OFF, all
                                      // other values switched ON!

     .  If the switch is set to on, then interrupt 16 (10h, video) and
        function 19 (13h, write string), normally only available on AT's,
        become available on PC XT's.

 Examples

     .  Do not reroute other program output to the selected window:

        DSETWINDOW(.F.)

     .  Do a test to see if ANSI.SYS has been linked in to CONFIG.SYS:

        lVar  :=  DSETWINDOW(.F.)
        ? ISANSI()
        DSETWINDOW(lVar)              // Reset to old status