GFNTSET()
 Set an already loaded font as active
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 Syntax

     GFNTSET(<aFont>, [<nClipTop>, <nClipBottom>])
        --> aClipInfo

 Arguments

     <aFont> represents the pointer to the VMM region where the .FND font
     is loaded.  <aFont> would have been created with GFNTLOAD().

     <nClipTop> and <nClipBottom> specify how many pixel rows to use
     when displaying standard text output.  This provides the ability to
     display a one pixel frame around a GET.

 Returns

     GFNTSET() returns a two-element array containing font clipping
     information.

 Description

     GFNTSET() sets an already loaded font as active.  When GFNTSET() is
     called, all subsequent DEVOUT() calls will use the new font.  This means
     that you can use multiple .FND fonts at the same time.  To go back to
     the standard ROM font, use GFNTSET( LLG_FNT_ROM ).  You can also use an
     .FND font in a GWRITEAT() as shown in the following code:

        aFndFont := GFNTLOAD("TestFnd.FND")
        nColor   := 3
        GWRITEAT(1, 1, "This is some text", nColor, LLG_MODE_SET, aFndFont)

     GFNTSET() returns a two-element array containing font clipping
     information.  The structure of this array is { nTopPixelRow,
     nBottomPixelRow }.  This feature allows text to fit at a reduced height.
     A common requirement is to draw a frame around a GET without having to
     use a full text line over and under the GET.  When you display a
     character with a DEVOUT() or a GET display method, the background always
     gets overwritten.  So, if a frame is precisely drawn around the GET,
     part of the frame will be overwritten as soon as a single character is
     displayed.

     In general, all regular fonts do not use the top and bottom row of
     pixels.  This allows a displayed character to be clipped or restricted
     so that DEVPOS()/DISPLAY() will only erase the lines 1-14 (instead of 0-
     15) and will preserve the frame previously drawn.

 Examples

     .  This example loads a font file called MyFont.FND:

        FUNCTION ShowOneFont (cString)
           LOCAL aFontBig, aFontSmall
                    // Load a couple of fonts into memory
           aFontBig    := GFNTLOAD("BigFnt.FND")
           aFontSmall  := GFNTLOAD("SmallFnt.FND")
                    // Set the BigFnt.FND to be active.  As soon as
        GFNTSET() is
                    // called, @...SAY, DEVOUT() etc. will use the new
        font.
           GFNTSET(aFontBig)
           @1,1 SAY "This text should appear in the font 'BigFnt.FND'"
                    // Display something in a Big font
           GWRITEAT(X , Y , "Using Big Font...",   nColor, LLG_MODE_SET)
           GWRITEAT(X , Y , "Using Small Font...", nColor, LLG_MODE_SET,;
        aFontSmall)
                    // Set the SmallFnt.FND to be active
           GFNTSET(aFontSmall)
                    // Display something in a Small font
           GWRITEAT(X , Y , "Using Small Font...", nColor, G_MODE_SET)
                    // Use the standard ROM font
           GFNTSET(G_FNT_ROM)
                    // Display something
           GWRITEAT(X , Y , "Using ROM Font...", nColor, G_MODE_SET)
                    // *Important*  You must erase the fonts from memory
        // if it is no
                    // longer used.  This is because CA-Clipper's VMM is
        // unable to free
                    // the memory occupied by aFont
           GFNTERASE(aFontBig)
           GFNTERASE(aFontSmall)
           RETURN  NIL

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