The RECT structure is a combination of four 4-byte numeric values.

typedef struct _RECT {
LONG left; 
LONG top; 
LONG right; 
LONG bottom; 
} RECT, *PRECT;

You can not pass this structure to an API function using a VFP array, since the array element occupies more than four bytes. Use STRING instead.

For example, a numeric value 43981 can be converted into in 4-byte LONG value as

Chr(13) + Chr(12) + Chr(11) + Chr(10)

Why? Because 43981 in hex notation is presented as 0xABCD. This is it. You just assemble four bytes -- from LOwest to HIghest:

0xd = 13
0xc = 12
0xb = 11
0xa = 10

So if you need to assemble the RECT structure with (10,0,100,100) do this:

cRECT = Chr(10) + Chr(0) + Chr(0) + Chr(0) +;
   Chr(0) + Chr(0) + Chr(0) + Chr(0) +;
   Chr(100) + Chr(0) + Chr(0) + Chr(0) +;
   Chr(100) + Chr(0) + Chr(0) + Chr(0)

And such input parameter must be declared as STRING or STRING @. So your declaration should look like the following:

DECLARE INTEGER IS3DrawSmoothTextOnRGB IN ISource30
	INTEGER @ pRGB,;
	LONG      uWidth,;
	LONG      uHeight,;
	LONG      uRowStride,;
	STRING  @ pText,;
	STRING  @ pFontName,;
	LONG      uFontHeight,;
	LONG      uSmoothingFactor,;
	STRING  @ pTextRect,;
	LONG      uDrawFlags,;
	LONG      uFlags,;
	INTEGER   textColor

All parameters passed by reference must be allocated before calling external function.

Here is a sample FoxPro code: Clipping mouse cursor area
http://www.news2news.com/vfp/?example=80

Notice that the ClipCursor accepts RECT structure as an input parameter and the GetClipCursor function returns data in a RECT structure.