SETPAGE()
 Selects a new screen page
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 Syntax

     SETPAGE(<nScreenPage>,[<lHidden>]) --> lSwitched

 Arguments

     <nScreenPage>  Designates the screen page number to select.  The
     value can be as high as you like, depending on the screen card, its
     mode, and available memory.  The first page is 0.

     <lHidden>  Designates whether or not output is displayed.  If this
     parameter is .T., the output is in the page selected, but is not
     displayed.  If this parameter is .F., the output is displayed.  The
     default value is .F..

 Returns

     SETPAGE() returns .T. when it is possible to physically or virtually
     select the screen page.

 Description

     SETPAGE() allows you to switch to another screen page on the video
     adapter that you use.  If the <lHidden> parameter is not passed (or is
     designated as .F.), the output, and therefore the selected page, is
     visible.  By contrast, if <lHidden> is .T., the output is sent to the
     new page, but the page that was visible when you invoked SETPAGE()
     remains visible.  It is therefore possible to construct hidden screens.

 Notes

     Important!  This function cannot be implemented when windows are
     open.

     .  Virtual screen output cannot be achieved using a string output
        (i.e. SETSCRSTR()).  Use SETSCRSTR() when there is only one page
        available on the screen adapter.

 Examples

     .  Select two pages with the output immediately visible.  The
        output with the returned value is on the new page:

        ? SETPAGE(1)            // .T., if OK

     .  Hide the output:

        SETPAGE(0)              // Displayed
        SETPAGE(1, .T.)         // Output here