From e616324683b33d7e911745a19cf202d1f609dfc4 Mon Sep 17 00:00:00 2001
From: Paul Davis <paul@linuxaudiosystems.com>
Date: Fri, 20 Jan 2017 12:08:58 +0100
Subject: [PATCH] add basic data members and methods for adding an explicit
 size allocation for Canvas::Item

---
 libs/canvas/canvas/item.h | 14 +++++++++++++-
 libs/canvas/item.cc       | 14 +++++++++++++-
 2 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/libs/canvas/canvas/item.h b/libs/canvas/canvas/item.h
index 517b4401ba..a480ec38a1 100644
--- a/libs/canvas/canvas/item.h
+++ b/libs/canvas/canvas/item.h
@@ -136,7 +136,18 @@ public:
 
 	ScrollGroup* scroll_parent() const { return _scroll_parent; }
 
-	Rect bounding_box () const;
+	/* item implementations can override this if they need to */
+	virtual Rect size_request() const { return bounding_box (true); }
+	void size_allocate (Rect const&);
+
+	/** bounding box is the public API to get the size of the item.
+	   If @param for_own_purposes is false, then it will return the
+	   allocated bounding box (if there is one) in preference to the
+	   one that would naturally be computed by the item.
+	*/
+	Rect bounding_box (bool for_own_purposes = false) const;
+	Rect allocation() const { return _allocation; }
+
         Coord height() const;
         Coord width() const;
 
@@ -281,6 +292,7 @@ protected:
 	mutable Rect _bounding_box;
 	/** true if _bounding_box might be out of date, false if its definitely not */
 	mutable bool _bounding_box_dirty;
+	Rect _allocation;
 
 	/* XXX: this is a bit grubby */
 	std::map<std::string, void *> _data;
diff --git a/libs/canvas/item.cc b/libs/canvas/item.cc
index 06ad24f2e6..589f1214b7 100644
--- a/libs/canvas/item.cc
+++ b/libs/canvas/item.cc
@@ -571,9 +571,15 @@ Item::grab_focus ()
 	/* XXX */
 }
 
+void
+Item::size_allocate (Rect const & r)
+{
+	_allocation = r;
+}
+
 /** @return Bounding box in this item's coordinates */
 ArdourCanvas::Rect
-Item::bounding_box () const
+Item::bounding_box (bool for_own_purposes) const
 {
 	if (_bounding_box_dirty) {
 		compute_bounding_box ();
@@ -581,6 +587,12 @@ Item::bounding_box () const
 		add_child_bounding_boxes ();
 	}
 
+	if (!for_own_purposes) {
+		if (_allocation) {
+			return _allocation;
+		}
+	}
+
 	return _bounding_box;
 }
 
-- 
2.30.2