TIP#168 implementation. Based on [Patch 886240]

6 files changed, 470 insertions, 56 deletions

diff --git a/ChangeLog b/ChangeLog
index 949ccfd..0a1180e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,18 @@
+2004-08-19  Donal K. Fellows  <donal.k.fellows@man.ac.uk>
+
+	TIP#168 IMPLEMENTATION
+
+	* generic/tkTrig.c (TkMakeRawCurve, TkMakeRawCurvePostscript):
+	* generic/tkInt.decls: New functions to handle the geometry for
+	"raw" bezier curves.
+	* generic/tkCanvUtil.c (tkRawSmoothMethod, InitSmoothMethods)
+	(TkSmoothParseProc): Add new type of smoothing method, simplify
+	the method initialization, and change the old smoothing method to
+	be called "true" and just keep "bezier" as an alias.
+	* tests/canvas.test (canvas-17.1): Basic test of built-in
+	smoothing method support.
+	* doc/canvas.n: Documentation updates.
+
 2004-08-18  Donal K. Fellows  <donal.k.fellows@man.ac.uk>
 
 	* generic/tkPanedWindow.c (optionSpecs): Add missing GEOMETRY flag
diff --git a/doc/canvas.n b/doc/canvas.n
index a9bee5f..7403907 100644
--- a/doc/canvas.n
+++ b/doc/canvas.n
@@ -6,7 +6,7 @@
 '\" See the file "license.terms" for information on usage and redistribution
 '\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
 '\" 
-'\" RCS: @(#) $Id: canvas.n,v 1.15 2004/08/16 08:24:45 dkf Exp $
+'\" RCS: @(#) $Id: canvas.n,v 1.16 2004/08/19 14:41:52 dkf Exp $
 '\"
 .so man.macros
 .TH canvas n 8.3 Tk "Tk Built-In Commands"
@@ -1396,20 +1396,29 @@ irrelevant.
 .TP
 \fB\-smooth \fIsmoothMethod\fR
 \fIsmoothMethod\fR must have one of the forms accepted by
-\fBTk_GetBoolean\fR or a line smoothing method.  Only \fBbezier\fR is
-supported in the core, but more can be added at runtime.  If a boolean
+\fBTk_GetBoolean\fR or a line smoothing method.  Only \fBtrue\fR and \fBraw\fR are
+supported in the core (with \fBbezier\fR being an alias for \fBtrue\fR), but more can be added at runtime.  If a boolean
 false value or empty string is given, no smoothing is applied.  A boolean
-truth value assumes \fBbezier\fR smoothing.
-It indicates whether or not the line should be drawn as a curve.
-If so, the line is rendered as a set of parabolic splines: one spline
+truth value assumes \fBtrue\fR smoothing.
+If the smoothing method is \fBtrue\fR, this indicates that the line
+should be drawn as a curve, rendered as a set of quadratic splines: one spline
 is drawn for the first and second line segments, one for the second
 and third, and so on.  Straight-line segments can be generated within
 a curve by duplicating the end-points of the desired line segment.
+If the smoothing method is \fBraw\fR, this indicates that the line
+should also be drawn as a curve but where the list of coordinates is
+such that the first coordinate pair (and every third coordinate pair
+thereafter) is a knot point on a cubic Bezier curve, and the other
+coordinates are control points on the cubic Bezier curve.  Straight
+line segments can be venerated within a curve by making control points
+equal to their neighbouring knot points.  If the last point is a
+control point and not a knot point, the point is repeated (one or two
+times) so that it also becomes a knot point.
 .TP
 \fB\-splinesteps \fInumber\fR
 Specifies the degree of smoothness desired for curves:  each spline
 will be approximated with \fInumber\fR line segments.  This
-option is ignored unless the \fB\-smooth\fR option is true.
+option is ignored unless the \fB\-smooth\fR option is true or \fBraw\fR.
 .SH "OVAL ITEMS"
 .PP
 Items of type \fBoval\fR appear as circular or oval regions on
@@ -1516,17 +1525,30 @@ If this option isn't specified then it defaults to \fBmiter\fR.
 .TP
 \fB\-smooth \fIboolean\fR
 \fIBoolean\fR must have one of the forms accepted by \fBTk_GetBoolean\fR
-It indicates whether or not the polygon should be drawn with a
-curved perimeter.
-If so, the outline of the polygon becomes a set of parabolic splines,
-one spline for the first and second line segments, one for the second
-and third, and so on.  Straight-line segments can be generated in a
-smoothed polygon by duplicating the end-points of the desired line segment.
+or a line smoothing method. Only \fBtrue\fR and \fBraw\fR are
+supported in the core (with \fBbezier\fR being an alias for \fBtrue\fR), but more can be added at runtime.  If a boolean
+false value or empty string is given, no smoothing is applied.  A boolean
+truth value assumes \fBtrue\fR smoothing.
+If the smoothing method is \fBtrue\fR, this indicates that the polygon
+should be drawn as a curve, rendered as a set of quadratic splines: one spline
+is drawn for the first and second line segments, one for the second
+and third, and so on.  Straight-line segments can be generated within
+a curve by duplicating the end-points of the desired line segment.
+If the smoothing method is \fBraw\fR, this indicates that the polygon
+should also be drawn as a curve but where the list of coordinates is
+such that the first coordinate pair (and every third coordinate pair
+thereafter) is a knot point on a cubic Bezier curve, and the other
+coordinates are control points on the cubic Bezier curve.  Straight
+line segments can be venerated within a curve by making control points
+equal to their neighbouring knot points.  If the last point is not the
+second point of a pair of control points, the point is repeated (one or two
+times) so that it also becomes the second point of a pair of control
+points (the associated knot point will be the first control point).
 .TP
 \fB\-splinesteps \fInumber\fR
 Specifies the degree of smoothness desired for curves:  each spline
 will be approximated with \fInumber\fR line segments.  This
-option is ignored unless the \fB\-smooth\fR option is true.
+option is ignored unless the \fB\-smooth\fR option is true or \fBraw\fR.
 .PP
 Polygon items are different from other items such as rectangles, ovals
 and arcs in that interior points are considered to be ``inside'' a
diff --git a/generic/tkCanvUtil.c b/generic/tkCanvUtil.c
index ceabca4..ff0d720 100644
--- a/generic/tkCanvUtil.c
+++ b/generic/tkCanvUtil.c
@@ -10,7 +10,7 @@
  * See the file "license.terms" for information on usage and redistribution
  * of this file, and for a DISCLAIMER OF ALL WARRANTIES.
  *
- * RCS: @(#) $Id: tkCanvUtil.c,v 1.11 2004/03/16 19:53:18 hobbs Exp $
+ * RCS: @(#) $Id: tkCanvUtil.c,v 1.12 2004/08/19 14:41:52 dkf Exp $
  */
 
 #include "tkInt.h"
@@ -18,6 +18,45 @@
 #include "tkPort.h"
 #include <assert.h>
 
+/*
+ * Structures defined only in this file.
+ */
+
+typedef struct SmoothAssocData {
+    struct SmoothAssocData *nextPtr;	/* pointer to next SmoothAssocData */
+    Tk_SmoothMethod smooth;		/* name and functions associated with
+					 * this option */
+} SmoothAssocData;
+
+Tk_SmoothMethod tkBezierSmoothMethod = {
+    "true",
+    TkMakeBezierCurve,
+    (void (*) _ANSI_ARGS_((Tcl_Interp *interp, Tk_Canvas canvas,
+	    double *coordPtr, int numPoints, int numSteps)))
+		TkMakeBezierPostscript,
+};
+static Tk_SmoothMethod tkRawSmoothMethod = {
+    "raw",
+    TkMakeRawCurve,
+    (void (*) _ANSI_ARGS_((Tcl_Interp *interp, Tk_Canvas canvas,
+	    double *coordPtr, int numPoints, int numSteps)))
+		TkMakeRawCurvePostscript,
+};
+
+/*
+ * Function forward-declarations.
+ */
+
+static void		SmoothMethodCleanupProc _ANSI_ARGS_((
+			    ClientData clientData, Tcl_Interp *interp));
+static SmoothAssocData *InitSmoothMethods _ANSI_ARGS_((Tcl_Interp *interp));
+static int		DashConvert _ANSI_ARGS_((char *l, CONST char *p,
+			    int n, double width));
+static void		translateAndAppendCoords _ANSI_ARGS_((
+			    TkCanvas *canvPtr, double x, double y,
+			    XPoint *outArr, int numOut));
+
+#define ABS(a) ((a>=0)?(a):(-(a)))
 
 /*
  *----------------------------------------------------------------------
@@ -458,11 +497,6 @@ Tk_CanvasTagsPrintProc(clientData, tkwin, widgRec, offset, freeProcPtr)
     return Tcl_Merge(itemPtr->numTags, (CONST char **) itemPtr->tagPtr);
 }
 
-
-static int	DashConvert _ANSI_ARGS_((char *l, CONST char *p,
-			int n, double width));
-#define ABS(a) ((a>=0)?(a):(-(a)))
-
 /*
  *--------------------------------------------------------------
  *
@@ -557,6 +591,49 @@ TkCanvasDashPrintProc(clientData, tkwin, widgRec, offset, freeProcPtr)
 /*
  *--------------------------------------------------------------
  *
+ * InitSmoothMethods --
+ *
+ *	This procedure is invoked to set up the initial state of the
+ *	list of "-smooth" methods.  It should only be called when the
+ *	list installed in the interpreter is NULL.
+ *
+ * Results:
+ *	Pointer to the start of the list of default smooth methods.
+ *
+ * Side effects:
+ *	A linked list of smooth methods is created and attached to the
+ *	interpreter's association key "smoothMethod"
+ *
+ *--------------------------------------------------------------
+ */
+
+static SmoothAssocData *
+InitSmoothMethods(interp)
+    Tcl_Interp *interp;
+{
+    SmoothAssocData *methods, *ptr;
+
+    methods = (SmoothAssocData *) ckalloc(sizeof(SmoothAssocData));
+    methods->smooth.name = tkRawSmoothMethod.name;
+    methods->smooth.coordProc = tkRawSmoothMethod.coordProc;
+    methods->smooth.postscriptProc = tkRawSmoothMethod.postscriptProc;
+
+    methods->nextPtr = (SmoothAssocData *) ckalloc(sizeof(SmoothAssocData));
+
+    ptr = methods->nextPtr;
+    ptr->smooth.name = tkBezierSmoothMethod.name;
+    ptr->smooth.coordProc = tkBezierSmoothMethod.coordProc;
+    ptr->smooth.postscriptProc = tkBezierSmoothMethod.postscriptProc;
+    ptr->nextPtr = NULL;
+
+    Tcl_SetAssocData(interp, "smoothMethod", SmoothMethodCleanupProc,
+		(ClientData) methods);
+    return methods;
+}
+
+/*
+ *--------------------------------------------------------------
+ *
  * Tk_CreateSmoothMethod --
  *
  *	This procedure is invoked to add additional values
@@ -572,23 +649,6 @@ TkCanvasDashPrintProc(clientData, tkwin, widgRec, offset, freeProcPtr)
  *--------------------------------------------------------------
  */
 
-Tk_SmoothMethod tkBezierSmoothMethod = {
-    "bezier",
-    TkMakeBezierCurve,
-    (void (*) _ANSI_ARGS_((Tcl_Interp *interp, Tk_Canvas canvas,
-	    double *coordPtr, int numPoints, int numSteps)))
-		TkMakeBezierPostscript,
-};
-
-static void SmoothMethodCleanupProc _ANSI_ARGS_((ClientData clientData,
-		Tcl_Interp *interp));
-
-typedef struct SmoothAssocData {
-    struct SmoothAssocData *nextPtr;	/* pointer to next SmoothAssocData */
-    Tk_SmoothMethod smooth;		/* name and functions associated with this
-					 * option */
-} SmoothAssocData;
-
 void
 Tk_CreateSmoothMethod(interp, smooth)
     Tcl_Interp *interp;
@@ -599,6 +659,14 @@ Tk_CreateSmoothMethod(interp, smooth)
 	    (Tcl_InterpDeleteProc **) NULL);
 
     /*
+     * Initialize if we were not previously initialized.
+     */
+
+    if (methods == NULL) {
+	methods = InitSmoothMethods(interp);
+    }
+
+    /*
      * If there's already a smooth method with the given name, remove it.
      */
 
@@ -680,7 +748,7 @@ TkSmoothParseProc(clientData, interp, tkwin, value, widgRec, offset)
     int offset;				/* Offset into item. */
 {
     register Tk_SmoothMethod **smoothPtr =
-	(Tk_SmoothMethod **) (widgRec + offset);
+	    (Tk_SmoothMethod **) (widgRec + offset);
     Tk_SmoothMethod *smooth = NULL;
     int b;
     size_t length;
@@ -693,10 +761,22 @@ TkSmoothParseProc(clientData, interp, tkwin, value, widgRec, offset)
     length = strlen(value);
     methods = (SmoothAssocData *) Tcl_GetAssocData(interp, "smoothMethod",
 	    (Tcl_InterpDeleteProc **) NULL);
+    /*
+     * Not initialized yet; fix that now.
+     */
+    if (methods == NULL) {
+	methods = InitSmoothMethods(interp);
+    }
+    /*
+     * Backward compatability hack
+     */
+    if (strncmp(value, "bezier", length) == 0) {
+	smooth = &tkBezierSmoothMethod;
+    }
     while (methods != (SmoothAssocData *) NULL) {
 	if (strncmp(value, methods->smooth.name, length) == 0) {
 	    if (smooth != (Tk_SmoothMethod *) NULL) {
-		Tcl_AppendResult(interp, "ambigeous smooth method \"", value,
+		Tcl_AppendResult(interp, "ambiguous smooth method \"", value,
 			"\"", (char *) NULL);
 		return TCL_ERROR;
 	    }
@@ -707,15 +787,8 @@ TkSmoothParseProc(clientData, interp, tkwin, value, widgRec, offset)
     if (smooth) {
 	*smoothPtr = smooth;
 	return TCL_OK;
-    } else if (strncmp(value, tkBezierSmoothMethod.name, length) == 0) {
-	/*
-	 * We need to do handle the built-in bezier method.
-	 */
-	*smoothPtr = &tkBezierSmoothMethod;
-	return TCL_OK;
     }
 
-
     if (Tcl_GetBoolean(interp, (char *) value, &b) != TCL_OK) {
 	return TCL_ERROR;
     }
diff --git a/generic/tkInt.decls b/generic/tkInt.decls
index ebfae12..12a560d 100644
--- a/generic/tkInt.decls
+++ b/generic/tkInt.decls
@@ -9,7 +9,7 @@
 # See the file "license.terms" for information on usage and redistribution
 # of this file, and for a DISCLAIMER OF ALL WARRANTIES.
 # 
-# RCS: @(#) $Id: tkInt.decls,v 1.35 2004/03/17 18:15:43 das Exp $
+# RCS: @(#) $Id: tkInt.decls,v 1.36 2004/08/19 14:41:52 dkf Exp $
 
 library tk
 
@@ -630,7 +630,18 @@ declare 148 generic {
 
 declare 149 generic {
     CONST Tk_OptionSpec * TkGetOptionSpec (CONST char *name,
-					   Tk_OptionTable optionTable)
+	    Tk_OptionTable optionTable)
+}
+
+# TIP#168
+declare 150 generic {
+    int TkMakeRawCurve (Tk_Canvas canvas,
+	    double *pointPtr, int numPoints, int numSteps,
+	    XPoint xPoints[], double dblPoints[])
+}
+declare 151 generic {
+    void TkMakeRawCurvePostscript (Tcl_Interp *interp,
+	    Tk_Canvas canvas, double *pointPtr, int numPoints)
 }
 
 ##############################################################################
diff --git a/generic/tkTrig.c b/generic/tkTrig.c
index b8a88e7..f3561b1 100644
--- a/generic/tkTrig.c
+++ b/generic/tkTrig.c
@@ -12,7 +12,7 @@
  * See the file "license.terms" for information on usage and redistribution
  * of this file, and for a DISCLAIMER OF ALL WARRANTIES.
  *
- * RCS: @(#) $Id: tkTrig.c,v 1.4 1999/12/14 06:52:33 hobbs Exp $
+ * RCS: @(#) $Id: tkTrig.c,v 1.5 2004/08/19 14:41:52 dkf Exp $
  */
 
 #include <stdio.h>
@@ -918,7 +918,7 @@ TkIncludePoint(itemPtr, pointPtr)
  * TkBezierScreenPoints --
  *
  *	Given four control points, create a larger set of XPoints
- *	for a Bezier spline based on the points.
+ *	for a Bezier curve based on the points.
  *
  * Results:
  *	The array at *xPointPtr gets filled in with numSteps XPoints
@@ -969,7 +969,7 @@ TkBezierScreenPoints(canvas, control, numSteps, xPointPtr)
  * TkBezierPoints --
  *
  *	Given four control points, create a larger set of points
- *	for a Bezier spline based on the points.
+ *	for a Bezier curve based on the points.
  *
  * Results:
  *	The array at *coordPtr gets filled in with 2*numSteps
@@ -1019,10 +1019,12 @@ TkBezierPoints(control, numSteps, coordPtr)
  *	parabolic splines to the line segments connecting the original
  *	points.  Produces output points in either of two forms.
  *
- *	Note: in spite of this procedure's name, it does *not* generate
- *	Bezier curves.  Since only three control points are used for
- *	each curve segment, not four, the curves are actually just
- *	parabolic.
+ *	Note: the name of this procedure should *not* be taken to 
+ *	mean that it interprets the input points as directly defining
+ *	Bezier curves.  Rather, it internally computes a Bezier curve
+ *	representation of each parabolic spline segment. (These 
+ *	Bezier curves are then flattened to produce the points 
+ *	filled into the output arrays.)
  *
  * Results:
  *	Either or both of the xPoints or dblPoints arrays are filled
@@ -1196,6 +1198,185 @@ TkMakeBezierCurve(canvas, pointPtr, numPoints, numSteps, xPoints, dblPoints)
 /*
  *--------------------------------------------------------------
  *
+ * TkMakeRawCurve --
+ *
+ *	Interpret the given set of points as the raw knots and
+ *	control points defining a sequence of cubic Bezier curves.
+ *	Create a new set of points that fit these Bezier curves.
+ *	Output points are produced in either of two forms.
+ *
+ * Results:
+ *	Either or both of the xPoints or dblPoints arrays are filled
+ *	in.  The return value is the number of points placed in the
+ *	arrays.
+ *
+ * Side effects:
+ *	None.
+ *
+ *--------------------------------------------------------------
+ */
+
+int
+TkMakeRawCurve(canvas, pointPtr, numPoints, numSteps, xPoints, dblPoints)
+    Tk_Canvas canvas;			/* Canvas in which curve is to be
+					 * drawn. */
+    double *pointPtr;			/* Array of input coordinates:  x0,
+					 * y0, x1, y1, etc.. */
+    int numPoints;			/* Number of points at pointPtr. */
+    int numSteps;			/* Number of steps to use for each
+					 * curve segment (determines
+					 * smoothness of curve). */
+    XPoint xPoints[];			/* Array of XPoints to fill in (e.g.
+					 * for display.  NULL means don't
+					 * fill in any XPoints. */
+    double dblPoints[];			/* Array of points to fill in as
+					 * doubles, in the form x0, y0,
+					 * x1, y1, ....  NULL means don't
+					 * fill in anything in this form.
+					 * Caller must make sure that this
+					 * array has enough space. */
+{
+    int outputPoints, i;
+    int numSegments = (numPoints+1)/3;
+    double *segPtr;
+
+    /*
+     * The input describes a curve with s Bezier curve segments if
+     * there are 3s+1, 3s, or 3s-1 input points. In the last two
+     * cases, 1 or 2 initial points from the first curve segment
+     * are reused as defining points also for the last curve segment.
+     * In the case of 3s input points, this will automatically close
+     * the curve.
+     */
+
+    if (!pointPtr) {
+	/*
+	 * If pointPtr == NULL, this function returns an upper limit.
+	 * of the array size to store the coordinates. This can be
+	 * used to allocate storage, before the actual coordinates
+	 * are calculated.
+	 */
+	return 1 + numSegments * numSteps;
+    }
+
+    outputPoints = 0;
+    if (xPoints != NULL) {
+	Tk_CanvasDrawableCoords(canvas, pointPtr[0], pointPtr[1],
+		&xPoints->x, &xPoints->y);
+	xPoints += 1;
+    }
+    if (dblPoints != NULL) {
+	dblPoints[0] = pointPtr[0];
+	dblPoints[1] = pointPtr[1];
+	dblPoints += 2;
+    }
+    outputPoints += 1;
+
+    /*
+     * The next loop handles all curve segments except one that
+     * overlaps the end of the list of coordinates.
+     */
+
+    for (i=numPoints,segPtr=pointPtr ; i>=4 ; i-=3,segPtr+=6) {
+	if (segPtr[0]==segPtr[2] && segPtr[1]==segPtr[3] &&
+		segPtr[4]==segPtr[6] && segPtr[5]==segPtr[7]) {
+	    /*
+	     * The control points on this segment are equal to
+	     * their neighbouring knots, so this segment is just
+	     * a straight line. A single point is sufficient.
+	     */
+	    if (xPoints != NULL) {
+		Tk_CanvasDrawableCoords(canvas, segPtr[6], segPtr[7],
+			&xPoints->x, &xPoints->y);
+		xPoints += 1;
+	    }
+	    if (dblPoints != NULL) {
+		dblPoints[0] = segPtr[6];
+		dblPoints[1] = segPtr[7];
+		dblPoints += 2;
+	    }
+	    outputPoints += 1;
+	} else {
+	    /*
+	     * This is a generic Bezier curve segment.
+	     */
+	    if (xPoints != NULL) {
+		TkBezierScreenPoints(canvas, segPtr, numSteps, xPoints);
+		xPoints += numSteps;
+	    }
+	    if (dblPoints != NULL) {
+		TkBezierPoints(segPtr, numSteps, dblPoints);
+		dblPoints += 2*numSteps;
+	    }
+	    outputPoints += numSteps;
+	}
+    }
+
+    /*
+     * If at this point i>1, then there is some point which has not
+     * yet been used. Make another curve segment.
+     */
+
+    if (i>1) {
+	int j;
+	double control[8];
+
+	/*
+	 * Copy the relevant coordinates to control[], so that
+	 * it can be passed as a unit to e.g. TkBezierPoints.
+	 */
+
+	for (j=0; j<2*i; j++) {
+	    control[j] = segPtr[j];
+	}
+	for (; j<8; j++) {
+	    control[j] = pointPtr[j-2*i];
+	}
+
+	/*
+	 * Then we just do the same things as above.
+	 */
+
+	if (control[0]==control[2] && control[1]==control[3] &&
+		control[4]==control[6] && control[5]==control[7]) {
+	    /*
+	     * The control points on this segment are equal to
+	     * their neighbouring knots, so this segment is just
+	     * a straight line. A single point is sufficient.
+	     */
+	    if (xPoints != NULL) {
+		Tk_CanvasDrawableCoords(canvas, control[6], control[7],
+			&xPoints->x, &xPoints->y);
+		xPoints += 1;
+	    }
+	    if (dblPoints != NULL) {
+		dblPoints[0] = control[6];
+		dblPoints[1] = control[7];
+		dblPoints += 2;
+	    }
+	    outputPoints += 1;
+	} else {
+	    /*
+	     * This is a generic Bezier curve segment.
+	     */
+	    if (xPoints != NULL) {
+		TkBezierScreenPoints(canvas, control, numSteps, xPoints);
+		xPoints += numSteps;
+	    }
+	    if (dblPoints != NULL) {
+		TkBezierPoints(control, numSteps, dblPoints);
+		dblPoints += 2*numSteps;
+	    }
+	    outputPoints += numSteps;
+	}
+    }
+
+    return outputPoints;
+}
+
+/*
+ *--------------------------------------------------------------
+ *
  * TkMakeBezierPostscript --
  *
  *	This procedure generates Postscript commands that create
@@ -1293,6 +1474,108 @@ TkMakeBezierPostscript(interp, canvas, pointPtr, numPoints)
 /*
  *--------------------------------------------------------------
  *
+ * TkMakeRawCurvePostscript --
+ *
+ *	This procedure interprets the input points as the raw knot
+ *	and control points for a curve composed of Bezier curve
+ *	segments, just like TkMakeRawCurve. It generates Postscript
+ *	commands that create a path corresponding to this given curve.
+ *
+ * Results:
+ *	None.  Postscript commands to generate the path are appended
+ *	to the interp's result.
+ *
+ * Side effects:
+ *	None.
+ *
+ *--------------------------------------------------------------
+ */
+
+void
+TkMakeRawCurvePostscript(interp, canvas, pointPtr, numPoints)
+    Tcl_Interp *interp;			/* Interpreter in whose result the
+					 * Postscript is to be stored. */
+    Tk_Canvas canvas;			/* Canvas widget for which the
+					 * Postscript is being generated. */
+    double *pointPtr;			/* Array of input coordinates:  x0,
+					 * y0, x1, y1, etc.. */
+    int numPoints;			/* Number of points at pointPtr. */
+{
+    int i;
+    double *segPtr;
+    char buffer[200];
+
+    /*
+     * Put the first point into the path.
+     */
+
+    sprintf(buffer, "%.15g %.15g moveto\n",
+	    pointPtr[0], Tk_CanvasPsY(canvas, pointPtr[1]));
+    Tcl_AppendResult(interp, buffer, (char *) NULL);
+
+    /*
+     * Loop through all the remaining points in the curve, generating
+     * a straight line or curve section for every three of them.
+     */
+
+    for (i=numPoints-1,segPtr=pointPtr ; i>=3 ; i-=3,segPtr+=6) {
+	if (segPtr[0]==segPtr[2] && segPtr[1]==segPtr[3] &&
+		segPtr[4]==segPtr[6] && segPtr[5]==segPtr[7]) {
+	    /*
+	     * The control points on this segment are equal to
+	     * their neighbouring knots, so this segment is just
+	     * a straight line.
+	     */
+	    sprintf(buffer, "%.15g %.15g lineto\n",
+		    segPtr[6], Tk_CanvasPsY(canvas, segPtr[7]));
+	} else {
+	    /*
+	     * This is a generic Bezier curve segment.
+	     */
+	    sprintf(buffer, "%.15g %.15g %.15g %.15g %.15g %.15g curveto\n",
+		    segPtr[2], Tk_CanvasPsY(canvas, segPtr[3]),
+		    segPtr[4], Tk_CanvasPsY(canvas, segPtr[5]),
+		    segPtr[6], Tk_CanvasPsY(canvas, segPtr[7]));
+	}
+	Tcl_AppendResult(interp, buffer, (char *) NULL);
+    }
+
+    /*
+     * If there are any points left that haven't been used,
+     * then build the last segment and generate Postscript in
+     * the same way for that.
+     */
+
+    if (i>0) {
+	int j;
+	double control[8];
+
+	for (j=0; j<2*i+2; j++) {
+	    control[j] = segPtr[j];
+	}
+	for (; j<8; j++) {
+	    control[j] = pointPtr[j-2*i-2];
+	}
+
+	if (control[0]==control[2] && control[1]==control[3] &&
+		control[4]==control[6] && control[5]==control[7]) {
+	    /* Straight line */
+	    sprintf(buffer, "%.15g %.15g lineto\n",
+		    control[6], Tk_CanvasPsY(canvas, control[7]));
+	} else {
+	    /* Bezier curve segment */
+	    sprintf(buffer, "%.15g %.15g %.15g %.15g %.15g %.15g curveto\n",
+		    control[2], Tk_CanvasPsY(canvas, control[3]),
+		    control[4], Tk_CanvasPsY(canvas, control[5]),
+		    control[6], Tk_CanvasPsY(canvas, control[7]));
+	}
+	Tcl_AppendResult(interp, buffer, (char *) NULL);
+    }
+}
+
+/*
+ *--------------------------------------------------------------
+ *
  * TkGetMiterPoints --
  *
  *	Given three points forming an angle, compute the
diff --git a/tests/canvas.test b/tests/canvas.test
index efa6b16..84f18b3 100644
--- a/tests/canvas.test
+++ b/tests/canvas.test
@@ -6,7 +6,7 @@
 # Copyright (c) 1998-2000 Ajuba Solutions.
 # All rights reserved.
 #
-# RCS: @(#) $Id: canvas.test,v 1.19 2004/06/15 21:06:40 dkf Exp $
+# RCS: @(#) $Id: canvas.test,v 1.20 2004/08/19 14:41:52 dkf Exp $
 
 package require tcltest 2.1
 eval tcltest::configure $argv
@@ -476,6 +476,16 @@ test canvas-16.1 {arc coords check} {
     .c itemcget $id -start
 } {33.0}
 
+test canvas-17.1 {default smooth method handling} {
+    destroy .c; canvas .c
+    set id [.c create line {0 0 1 1 2 2 3 3 4 4 5 5 6 6}]
+    set result [.c itemcget $id -smooth]
+    foreach smoother {yes 1 bezier raw r b} {
+	.c itemconfigure $id -smooth $smoother
+	lappend result [.c itemcget $id -smooth]
+    }
+} {0 true true true raw raw true}
+
 destroy .c
 
 # cleanup