From: dooglus <dooglus@1f10aa63-cdf2-0310-b900-c93c546f37ac>
Date: Fri, 1 Feb 2008 01:58:45 +0000 (+0000)
Subject: I still think it would be great to get rid of reference counting - read the new comme... 
X-Git-Url: https://git.pterodactylus.net/?a=commitdiff_plain;h=9fa49a5c11359714a62afc430499897538b59cc4;p=synfig.git

I still think it would be great to get rid of reference counting - read the new comment in layer_pastecanvas.h and you'll almost certainly agree!


git-svn-id: http://svn.voria.com/code@1542 1f10aa63-cdf2-0310-b900-c93c546f37ac
---

diff --git a/synfig-core/trunk/src/synfig/layer_pastecanvas.cpp b/synfig-core/trunk/src/synfig/layer_pastecanvas.cpp
index 04ed8b9..edc3d0b 100644
--- a/synfig-core/trunk/src/synfig/layer_pastecanvas.cpp
+++ b/synfig-core/trunk/src/synfig/layer_pastecanvas.cpp
@@ -85,7 +85,8 @@ Layer_PasteCanvas::Layer_PasteCanvas():
 	origin(0,0),
 	depth(0),
 	zoom(0),
-	time_offset(0)
+	time_offset(0),
+	extra_reference(false)
 {
 	children_lock=false;
 	muck_with_time_=true;
@@ -103,6 +104,7 @@ Layer_PasteCanvas::~Layer_PasteCanvas()
 	set_sub_canvas(0);
 
 	//if(canvas && (canvas->is_inline() || !get_canvas() || get_canvas()->get_root()!=canvas->get_root()))
+	//if(extra_reference)
 	//	canvas->unref();
 }
 
@@ -186,7 +188,8 @@ Layer_PasteCanvas::set_sub_canvas(etl::handle<synfig::Canvas> x)
 	if(canvas && muck_with_time_)
 		remove_child(canvas.get());
 
-	if(canvas && (canvas->is_inline() || !get_canvas() || get_canvas()->get_root()!=canvas->get_root()))
+	// if(canvas && (canvas->is_inline() || !get_canvas() || get_canvas()->get_root()!=canvas->get_root()))
+	if (extra_reference)
 		canvas->unref();
 
 	child_changed_connection.disconnect();
@@ -209,7 +212,12 @@ Layer_PasteCanvas::set_sub_canvas(etl::handle<synfig::Canvas> x)
 		add_child(canvas.get());
 
 	if(canvas && (canvas->is_inline() || !get_canvas() || get_canvas()->get_root()!=canvas->get_root()))
+	{
 		canvas->ref();
+		extra_reference = true;
+	}
+	else
+		extra_reference = false;
 
 	if(canvas)
 		on_canvas_set();
diff --git a/synfig-core/trunk/src/synfig/layer_pastecanvas.h b/synfig-core/trunk/src/synfig/layer_pastecanvas.h
index 0aa3d6b..1dc9506 100644
--- a/synfig-core/trunk/src/synfig/layer_pastecanvas.h
+++ b/synfig-core/trunk/src/synfig/layer_pastecanvas.h
@@ -70,6 +70,33 @@ private:
 	mutable Rect bounds;
 
 	sigc::connection child_changed_connection;
+
+	// Nasty hack: Remember whether we called an extra ref() when
+	// setting the canvas, so we know whether to call an extra unref()
+	// when finished with the canvas.
+	//
+	// Here's the story:
+	//
+	// The root canvas is destructed first.  That sets the
+	// Layer::canvas_ (the parent canvas) of any PasteCanvas layer it
+	// contains to nil, due to a call to Layer::set_canvas(0),
+	// triggered by the connection made when Layer::set_canvas
+	// originally set its canvas_ member to point to the root canvas.
+	// ~Canvas does begin_delete() which triggers that connection.
+	//
+	// After ~Canvas has run, the members of the root canvas are
+	// freed, including its children_ list.  If this was the last
+	// reference to the child canvas that the pastecanvas uses, that
+	// child canvas will Layer_PasteCanvas::set_sub_canvas(0) on the
+	// PasteCanvas layer to set its canvas (the child, pasted canvas)
+	// not to refer to the soon-to-be destroys child canvas.  But
+	// set_sub_canvas() originally looked at the value of
+	// Layer::canvas_ (the parent canvas, obtained via
+	// Layer::get_canvas()) to decide whether to do an extra ref() on
+	// canvas (the child canvas).  We need to unref() it now if we
+	// did, but we've forgotten whether we did.  So we use this
+	// 'extra_reference' member to store that decision.
+	bool extra_reference;
 public:
 
 	virtual void on_canvas_set();