From c207b78d079803605d8aec2fe63a059fc4bdb2c6 Mon Sep 17 00:00:00 2001
From: Ori Bernstein <ori@eigenstate.org>
Date: Sat, 9 Jan 2021 12:20:49 -0800
Subject: [PATCH] libdraw: add bezierpts

This patch exposes the bezierpts function,
providing a way to get the points on a path,
similar how bezsplinepts gives them for b
splines.
---
 sys/include/draw.h       |  1 +
 sys/man/2/draw           | 12 ++++++++++++
 sys/src/libdraw/bezier.c | 17 ++++++++++++++---
 3 files changed, 27 insertions(+), 3 deletions(-)

diff --git a/sys/include/draw.h b/sys/include/draw.h
index 2200b0243..36a672bb4 100644
--- a/sys/include/draw.h
+++ b/sys/include/draw.h
@@ -436,6 +436,7 @@ extern Point	_string(Image*, Point, Image*, Point, Font*, char*, Rune*, int, Rec
 extern Point	stringsubfont(Image*, Point, Image*, Subfont*, char*);
 extern int		bezier(Image*, Point, Point, Point, Point, int, int, int, Image*, Point);
 extern int		bezierop(Image*, Point, Point, Point, Point, int, int, int, Image*, Point, Drawop);
+extern int		bezierpts(Point, Point, Point, Point, Point**);
 extern int		bezspline(Image*, Point*, int, int, int, int, Image*, Point);
 extern int		bezsplineop(Image*, Point*, int, int, int, int, Image*, Point, Drawop);
 extern int		bezsplinepts(Point*, int, Point**);
diff --git a/sys/man/2/draw b/sys/man/2/draw
index 79e7c0ddf..878ea3c6c 100644
--- a/sys/man/2/draw
+++ b/sys/man/2/draw
@@ -103,6 +103,8 @@ int	bezierop(Image *dst, Point p0, Point p1, Point p2, Point p3,
 		int end0, int end1, int radius, Image *src, Point sp,
 		Drawop op)
 .PB
+int	bezierpts(Point p0, Point p1, Point p2, Point p3, Point **pp)
+.PB
 int	bezspline(Image *dst, Point *pt, int npt, int end0, int end1,
 		int radius, Image *src, Point sp)
 .PB
@@ -603,6 +605,16 @@ corresponds to
 in
 .IR dst .
 .TP
+\f5bezierpts(\f2a\fP, \f2b\fP, \f2c\fP, \f2d\fP, \f2pp\fP)
+.I Bezierpts
+returns in
+.I pp
+a list of points making up the open polygon that
+.I bezier
+would draw.
+The caller is responsible for freeing
+.IR *pp .
+.TP
 \f5bezspline(\f2dst\fP, \f2p\fP, \f2np\fP, \f2end0\fP, \f2end1\fP, \f2thick\fP, \f2src\fP, \f2sp\fP)
 .I Bezspline
 takes the same arguments as
diff --git a/sys/src/libdraw/bezier.c b/sys/src/libdraw/bezier.c
index dca61bc0b..55465226c 100644
--- a/sys/src/libdraw/bezier.c
+++ b/sys/src/libdraw/bezier.c
@@ -98,12 +98,23 @@ bpts(Plist *l, Point p0, Point p1, Point p2, Point p3)
 }
 
 static void
-bezierpts(Plist *l, Point p0, Point p1, Point p2, Point p3)
+_bezierpts(Plist *l, Point p0, Point p1, Point p2, Point p3)
 {
 	bpts(l, p0, p1, p2, p3);
 	appendpt(l, p3);
 }
 
+int
+bezierpts(Point p0, Point p1, Point p2, Point p3, Point **pp)
+{
+	Plist l;
+	l.p = nil;
+	l.np = 0;
+	_bezierpts(&l, p0, p1, p2, p3);
+	*pp = l.p;
+	return l.np;
+}
+
 static void
 _bezsplinepts(Plist *l, Point *pt, int npt)
 {
@@ -167,7 +178,7 @@ bezierop(Image *dst, Point p0, Point p1, Point p2, Point p3, int end0, int end1,
 	Plist l;
 
 	l.np = 0;
-	bezierpts(&l, p0, p1, p2, p3);
+	_bezierpts(&l, p0, p1, p2, p3);
 	if(l.np == -1)
 		return 0;
 	if(l.np != 0){
@@ -211,7 +222,7 @@ fillbezierop(Image *dst, Point p0, Point p1, Point p2, Point p3, int w, Image *s
 	Plist l;
 
 	l.np = 0;
-	bezierpts(&l, p0, p1, p2, p3);
+	_bezierpts(&l, p0, p1, p2, p3);
 	if(l.np == -1)
 		return 0;
 	if(l.np != 0){