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                                Using Paths
 
You can use path functions to perform the following tasks:
 
♦  Draw a geometric line.
 
♦  Draw a filled polygon.
 
♦  Create a clip path.
 
Drawing a Geometric Line
 
To draw a geometric line, you must perform the following steps:
 
1  Set the geometric-line width by calling the GpiSetLineWidthGeom
   function.
 
2  Set the geometric-line-end style calling the GpiSetLineEnd function.
 
3  Start a path by calling the GpiBeginPath function.
 
4  Draw the line(s) by calling the GpiMove and GpiLine functions.
 
5  End the path by calling the GpiEndPath function.
 
6  Draw the line by calling the GpiStrokePath function.
 
The following code fragment shows how to draw a straight line that is 10
units wide and has round ends:
 
GpiSetLineWidthGeom(hps, 10L);      /* sets line width to 10  */
GpiSetLineEnd(hps, LINEEND_ROUND);  /* sets line end to round */
GpiBeginPath(hps, 1L);              /* begins path            */
ptl.x = 7; ptl.y = 15;
GpiMove(hps, &ptl);                 /* sets current position  */
ptl.x = 450; ptl.y = 15;
GpiLine(hps, &ptl);                 /* draws line             */
GpiEndPath(hps);                    /* ends path              */
GpiStrokePath(hps, 1L, 0L);         /* draws wide line        */
 
Drawing a Filled Polygon
 
To draw a filled polygon, you must perform the following steps:
 
1  Start a path by calling the GpiBeginPath function.
 
2  Move to the starting point by calling the GpiMove function.
 
3  Draw the boundary lines by calling the appropriate line-drawing
   function.
 
4  End the path by calling the GpiEndPath function.
 
5  Specify a fill mode and fill the path by calling the GpiFillPath
   function.
 
The following code fragment shows how to draw an empty triangle within a
solid rectangle:
 
POINTL aptl1 [4] = {           /* array of points for triangle  */
    50, 50,
    100, 100,
    150, 50,
    50, 50 };
 
POINTL aptl2[5] = {            /* array of points for rectangle */
    25, 25,
    25, 200,
    200, 200,
    200, 25,
    25, 25 };
 
GpiBeginPath(hps, 1L);                 /* begins path     */
GpiMove(hps, aptl1);      /* sets current position        */
GpiPolyLine(hps, 4,
    aptl1);               /* plots points for triangle    */
GpiMove(hps, aptl2);      /* sets current position        */
GpiPolyLine(hps, 5,
    aptl2);               /* plots points for rectangle   */
GpiEndPath(hps);          /* ends path                    */
GpiFillPath(hps, 1L,
    FPATH_ALTERNATE);     /* draws triangle and rectangle */
 
Creating a Clip Path
 
To create a clip path, you must perform the following steps:
 
1  Start a path by calling the GpiBeginPath function.
 
2  Draw the border of the path by calling the appropriate line or arc
   functions.
 
3  End the path by calling the GpiEndPath function.
 
4  Create the clip path by calling the GpiSetClipPath function.
 
The following code fragment shows how to create a triangular clip path and
then write text into it:
 
POINTL aptl[4] = {            /* array of points for triangle */
    35, 45,
    100, 100,
    200, 45,
    35, 45 };
 
GpiBeginPath(hps, 1L);       /* begins path bracket                 */
GpiMove(hps, aptl);          /* sets current position               */
GpiPolyLine(hps, 4, aptl);   /* plots points for triangle           */
GpiEndPath(hps);             /* ends path bracket                   */
 
GpiSetClipPath(hps, 1L, SCP_ALTERNATE | SCP_AND); /* sets clip path */
 
ptlStart.x = 50;
for (i = 50; i < 110; i = i + 10) {
    ptlStart.y = i;
 
    /* write the text */
 
    GpiCharStringAt(hps, &ptlStart, 18, "?!String of text!?");
  }
 
 
                                      ♦