From a6c1a3d9d0af4aefa73178272c470fd35b57b68d Mon Sep 17 00:00:00 2001
From: Paul Davis <paul@linuxaudiosystems.com>
Date: Wed, 21 Jun 2023 16:18:14 -0600
Subject: [PATCH] lollis: potentially clip circle with a bounding parent

---
 libs/canvas/canvas/lollipop.h |  3 +++
 libs/canvas/lollipop.cc       | 23 +++++++++++++++++++++--
 2 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/libs/canvas/canvas/lollipop.h b/libs/canvas/canvas/lollipop.h
index 714fb89404..4b6545924f 100644
--- a/libs/canvas/canvas/lollipop.h
+++ b/libs/canvas/canvas/lollipop.h
@@ -54,10 +54,13 @@ public:
 	Coord y0 () const { return _center.y; }
 	Coord y1 () const { return _center.y + _length; }
 
+	void set_bounding_parent (Item*);
+
   private:
 	Duple _center;
 	Coord _radius;
 	Coord _length;
+	Item* bounding_parent;
 };
 
 }
diff --git a/libs/canvas/lollipop.cc b/libs/canvas/lollipop.cc
index 140a3455fa..c2335e62f8 100644
--- a/libs/canvas/lollipop.cc
+++ b/libs/canvas/lollipop.cc
@@ -33,6 +33,7 @@ Lollipop::Lollipop (Canvas* c)
 	: Item (c)
 	, _radius (8)
 	, _length (0)
+	, bounding_parent (0)
 {
 }
 
@@ -40,9 +41,16 @@ Lollipop::Lollipop (Item* parent)
 	: Item (parent)
 	, _radius (8)
 	, _length (0)
+	, bounding_parent (0)
 {
 }
 
+void
+Lollipop::set_bounding_parent (Item* bp)
+{
+	bounding_parent = bp;
+}
+
 void
 Lollipop::compute_bounding_box () const
 {
@@ -67,10 +75,17 @@ Lollipop::render (Rect const & area, Cairo::RefPtr<Cairo::Context> context) cons
 	/* the line */
 
 	context->move_to (l.x, l.y + _radius);
-	context->line_to (l.x, l.y + _length - _radius);
+	context->line_to (l.x, l.y + _length);
 	context->stroke ();
 
-	/* the circle */
+	/* the circle: clip to avoid weirdness at top and bottom of parent */
+
+	if (bounding_parent) {
+		context->save ();
+		Rect b (bounding_parent->item_to_window (bounding_parent->bounding_box()));
+		context->rectangle (b.x0, b.y0, b.width(), b.height());
+		context->clip();
+	}
 
 	context->arc (p.x, p.y, _radius, 0.0 * (M_PI/180.0), 360.0 * (M_PI/180.0));
 
@@ -88,6 +103,10 @@ Lollipop::render (Rect const & area, Cairo::RefPtr<Cairo::Context> context) cons
 		context->stroke ();
 	}
 
+	if (bounding_parent) {
+		context->restore ();
+	}
+
 	render_children (area, context);
 }