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#define INCL_GPIPRIMITIVES
 
LONG GpiPolyFilletSharp(hps, cptl, aptl, afxSharpness)
HPS hps;                /* presentation-space handle                */
LONG cptl;              /* number of points                         */
PPOINTL aptl;           /* array of structures for points           */
PFIXED afxSharpness;    /* array of structures for sharpness values */
 
The GpiPolyFilletSharp function creates one or more fillets. The function
draws the fillets by using the control and end points specified by the aptl
parameter and the fillet sharpness values specified by the afxSharpness
parameter. The function draws the first fillet from the current position to
the first end point, by using the first control point and first sharpness
value to construct the path of the fillet. The second fillet is drawn from
the first end point to the second end point using the second control point
and sharpness values. The function continues with each successive point,
using the last end point as the starting point for the next fillet, until
the function draws one fillet for each control and end-point pair.
 
For each fillet, the array pointed to by aptl contains a control and
end-point pair. The first pair of points is the control and end points for
the first fillet, with the control point given first. The array pointed to
by afxSharpness contains the sharpness values for each fillet, with the
sharpness value for the first fillet given first.
 
The GpiPolyFilletSharp function moves the current position to the end point
of the last fillet.
 
Parameter     Description
────────────────────────────────────────────────────────────────────────────
 
hps           Identifies the presentation space.
 
cptl          Specifies the number of points in the array pointed to by
              aptl. This must be twice the number of fillets since each
              fillet requires a control and end-point pair.
 
aptl          Points to an array of POINTL structures that contain the
              points.
 
afxSharpness  Points to an array of sharpness values giving the sharpness of
              successive fillets. Each value must be a fixed-point value.
              Each value controls the type of curve drawn for the fillet. If
              this value is greater than 1.0, the curve is a hyperbola. If
              the value is 1.0, the curve is a parabola. If the value is
              less than 1.0, the curve is an ellipse.
 
Return Value
 
The return value is GPI_OK or GPI_HITS if the function is successful (it is
GPI_HITS if the detectable attribute is set for the presentation space and a
correlation hit occurs). The return value is GPI_ERROR if an error occurs.
 
Errors
 
Use the WinGetLastError function to retrieve the error value, which may be
one of the following:
 
     PMERR_INV_COORDINATE
     PMERR_INV_HPS
     PMERR_INV_LENGTH_OR_COUNT
     PMERR_INV_SHARPNESS_PARM
     PMERR_PS_BUSY
 
Comments
 
A fillet is a smooth curve whose path is controlled by three points: a start
point, an end point, and a control point. The smoothness of the fillet is
controlled by a sharpness value.
 
The GpiPolyFilletSharp function draws a fillet by first constructing two
imaginary straight lines, one from the start point to the control point and
another from the control point to the end point. The function then draws the
fillet from the start to end point, such that the first imaginary line is
tangent to the fillet at the current position and the second imaginary line
is tangent to the fillet at the end point.
 
GpiPolyFilletSharp uses the control point and the sharpness value to
determine the path of the curve. The function always draws the curve through
a fourth point. It locates the point by constructing two more imaginary
straight lines, one from the start to end point, and another from the
control point to the midpoint of this first line. The fourth point lies on
the imaginary line drawn from the control point to the midpoint. It is
placed such that the ratio of the lengths of the bottom and top pieces of
this line is equal to the sharpness value.
 
The maximum number of fillets allowed depends upon the length of coordinates
and is not less than 2000.
 
Example
 
This example uses the GpiPolyFilletSharp function to draw a curve with a
loop. The curve is drawn within a rectangle. The sharpness values are chosen
to draw the curve close to the control points.
 
POINTL ptlStart = { 0, 0 };
POINTL aptl[4] = { 100, 100, 200, 100, 0, 100, 200, 0 };
FIXED afx[2] = { MAKEFIXED(4, 0), MAKEFIXED(4, 0) };
 
GpiMove(hps, &ptlStart);   /* move to first starting point         */
GpiPolyFilletSharp(hps,    /* presentation-space handle            */
    4L,                    /* 4 points in the array                */
    aptl,                  /* address of array of points           */
    afx);                  /* address of array of sharpness values */
 
See Also
 
GpiMove, GpiPolyFillet, GpiPolyLine, GpiSetAttrs, GpiSetColor,
GpiSetCurrentPosition, GpiSetLineType, POINTL
 
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