stub constraint-based packer for canvas

libs/canvas/canvas/constraint_packer.h

@@ -0,0 +1,51 @@
+/*
+ * Copyright (C) 2020 Paul Davis <paul@linuxaudiosystems.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#ifndef __CANVAS_CONSTRAINT_PACKER_H__
+#define __CANVAS_CONSTRAINT_PACKER_H__
+
+#include "canvas/item.h"
+
+namespace ArdourCanvas
+{
+
+class Rectangle;
+
+class LIBCANVAS_API ConstraintPacker : public Item
+{
+public:
+	ConstraintPacker (Canvas *);
+	ConstraintPacker (Item *);
+
+	void compute_bounding_box () const;
+	void render (Rect const & area, Cairo::RefPtr<Cairo::Context> context) const;
+
+  protected:
+	void child_changed ();
+
+  private:
+	Rectangle *self;
+	bool collapse_on_hide;
+
+	void reset_self ();
+	void reposition_children ();
+};
+
+}
+
+#endif

libs/canvas/constraint_packer.cc

@@ -0,0 +1,90 @@
+/*
+ * Copyright (C) 2020 Paul Davis <paul@linuxaudiosystems.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include "kiwi/kiwi.h"
+
+#include "canvas/constraint_packer.h"
+#include "canvas/rectangle.h"
+
+using namespace ArdourCanvas;
+
+ConstraintPacker::ConstraintPacker (Canvas* canvas)
+	: Item (canvas)
+{
+}
+
+ConstraintPacker::ConstraintPacker (Item* parent)
+	: Item (parent)
+{
+}
+
+void
+ConstraintPacker::render (Rect const & area, Cairo::RefPtr<Cairo::Context> context) const
+{
+	Item::render_children (area, context);
+}
+
+void
+ConstraintPacker::compute_bounding_box () const
+{
+	_bounding_box = Rect();
+
+	if (_items.empty()) {
+		_bounding_box_dirty = false;
+		return;
+	}
+
+	add_child_bounding_boxes (!collapse_on_hide);
+
+	_bounding_box_dirty = false;
+}
+
+void
+ConstraintPacker::reset_self ()
+{
+	if (_bounding_box_dirty) {
+		compute_bounding_box ();
+	}
+
+	if (!_bounding_box) {
+		self->hide ();
+		return;
+	}
+
+	Rect r (_bounding_box);
+
+	/* XXX need to shrink by margin */
+
+	self->set (r);
+}
+
+void
+ConstraintPacker::reposition_children ()
+{
+	_bounding_box_dirty = true;
+	reset_self ();
+}
+void
+ConstraintPacker::child_changed ()
+{
+	/* catch visibility and size changes */
+
+	Item::child_changed ();
+	reposition_children ();
+}
+