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 DISPBOX()
 Display a box on the screen
------------------------------------------------------------------------------
 Syntax

     DISPBOX(<nTop>, <nLeft>, <nBottom>, <nRight>,
        [<cnBoxString>], [<cColorString>]) --> NIL

 Arguments

     <nTop>, <nLeft>, <nBottom>, and <nRight> define the
     coordinates of the box.  DISPBOX() draws a box using row values from
     zero to MAXROW(), and column values from zero to MAXCOL().  If <nBottom>
     and <nRight> are larger than MAXROW() and MAXCOL(), the bottom-right
     corner is drawn off the screen.

     <cnBoxString> is a numeric or character expression that defines the
     border characters of the box.  If specified as a numeric expression, a
     value of 1 displays a single-line box and a value of 2 displays a
     double-line box.  All other numeric values display a single-line box.

     If <cnBoxString> is a character expression, it specifies the characters
     to be used in drawing the box.  This is a string of eight border
     characters and a fill character.  If <cnBoxString> is specified as a
     single character, that character is used to draw the whole box.

     If this argument is not specified, a single-line box is drawn.

     <cColorString> defines the display color of the box that is drawn.
     If not specified, the box is drawn using the standard color setting of
     the current system color as defined by SETCOLOR().

 Returns

     DISPBOX() always returns NIL.

 Description

     DISPBOX() is a screen function that draws a box at the specified display
     coordinates in the specified color.  If you specify <cnBoxString>,
     DISPBOX() draws a box on the screen using configurable border and fill
     characters.  DISPBOX() draws the box using <cnBoxString> starting from
     the upper left-hand corner, proceeding clockwise and filling the screen
     region with the ninth character.  If the ninth character is not
     specified, the screen region within the box is not painted.  Existing
     text and color remain unchanged.

     In cases where cnBoxString respects CA-Clipper conventions, the behavior
     of DISPBOX() is unchanged.  The behavior of this function can easily be
     modified to take advantage of graphic mode.  For example, you can
     replace the standard window frames using single or double lines with new
     graphical frames that have an impressive 3-D look.  Simply replace the
     cBoxString parameter using the following:

     CHR(2) + CHR(nColor+1) // draws a box of thickness 16x8x16x8
     CHR(3) + CHR(nColor+1) // draws a box of thickness 8x8x8x8
     CHR(4) + CHR(nColor+1) // draws a box of thickness

                            // 16x16x16x16
     CHR(5) + CHR(nColor+1) // draws a box of thickness 16x8x8x8

     Note that <nColor> is a numeric color representation.  You must add 1 to
     this value.

     In general, CHR(2) + CHR(nColor+1) can be used instead of CA-Clipper's
     B_SINGLE or B_DOUBLE defines.

     CA-Clipper graphics comes with two #defines LLG_BOX_GRAY_STD and
     LLG_BOX_GRAY_SQUARE to allow gray (nColor=7) boxes of width 16x8 or
     16x16.

     You can completely customize the box by passing chr(1) + ... as the
     first parameter:

     CHR(1)             + ;  // Box entirely defined
     CHR(nBackColor+1)  + ;  // Color used as background fill
     CHR(nLightColor+1) + ;  // Color used to lighten the frame
     CHR(nDarkColor+1)  + ;  // Color used to darken the frame
     CHR(nWidthUp)      + ;  // Thickness of upper edge of box
     CHR(nWidthRight)   + ;  // Thickness of right edge of box
     CHR(nWidthDown)    + ;  // Thickness of lower edge of box
     CHR(nWidthLeft)         // Thickness of left edge of box

     After DISPBOX() executes, the cursor is located in the upper corner of
     the boxed region at <nTop> + 1 and <nLeft> + 1.  ROW() and COL() are
     also updated to reflect the new cursor position.

     Note that Box.ch, located in \CLIP53\INCLUDE, provides constants for
     various border configurations.

 Notes

     The number of colors available depends on the current video mode setting
     ( SET VIDEOMODE ).

 Examples

     .  This code example displays a double-line box using a numeric
        value to specify the box border:

        #define B_SINGLE   1
        #define B_DOUBLE   2
        //
        DISPBOX(1, 1, 10, 10, B_DOUBLE, "BG+/B")

     .  This example displays a single-line top and double-line side
        box by specifying border characters with a manifest constant defined
        in Box.ch:

        #include "Box.ch"
        //
        DISPBOX(1, 1, 10, 10, B_SINGLE_DOUBLE, "BG+/B")

     .  This example displays a box with a 3-D look.  It can be used
        for graphic mode:

        // Display a box with a 3D look of constant width 16x16x16x16
        DISPBOX( nTop, nLeft, nBottom, nRight, LLG_BOX_GRAY_SQUARE )
        // Write some transparent text in the 3D frame
        GWRITEAT(  nLeft * GMODE()[LLG_MODE_FONT_COL] ,;
        nTop  * GMODE()[LLG_MODE_FONT_ROW] ,;
        "This is some Text...",;
        4,;
        LLG_MODE_SET; )

 Files   Library is LLIBG.LIB, header file is Llibg.ch.