GSPenProtocol Protocol Reference
Tasks

– moveTo:
required method 
– lineTo:
required method 
– curveTo:off1:off2:
required method 
– qCurveTo:
required method 
– closePath
required method 
– endPath
required method 
– startGlyph:
Instance Methods
closePath
Close the current sub path. You must call either pen.closePath() or pen.endPath() after each sub path.
 (void)closePath
curveTo:off1:off2:
Draw a cubic bezier with an arbitrary number of control points.
 (void)curveTo:(NSPoint)pt off1:(NSPoint)off1 off2:(NSPoint)off2
Discussion
The last point specified is oncurve, all others are offcurve (control) points. If the number of control points is > 2, the segment is split into multiple bezier segments. This works like this:
Let n be the number of control points (which is the number of arguments to this call minus 1). If n==2, a plain vanilla cubic bezier is drawn. If n==1, we fall back to a quadratic segment and if n==0 we draw a straight line. It gets interesting when n>2: n1 PostScriptstyle cubic segments will be drawn as if it were one curve. See decomposeSuperBezierSegment().
The conversion algorithm used for n>2 is inspired by NURB splines, and is conceptually equivalent to the TrueType “implied points” principle. See also decomposeQuadraticSegment().
endPath
End the current sub path, but don’t close it. You must call either pen.closePath() or pen.endPath() after each sub path.
 (void)endPath
moveTo:
Begin a new sub path, set the current point to ‘pt’. You must end each sub path with a call to pen.closePath() or pen.endPath().
 (void)moveTo:(NSPoint)pt
qCurveTo:
Draw a whole string of quadratic curve segments.
 (void)qCurveTo:(NSArray *)Points
Discussion
The last point specified is oncurve, all others are offcurve points.
This method implements TrueTypestyle curves, breaking up curves using ‘implied points’: between each two consequtive offcurve points, there is one implied point exactly in the middle between them. See also decomposeQuadraticSegment().
The last argument (normally the oncurve point) may be None. This is to support contours that have NO oncurve points (a rarely seen feature of TrueType outlines).