new canvas item: RectSet

a collection of rectangles, conceptually similar to LineSet

this avoids keeping around N different Canvas::Rectangles and instead
collapses a related set of them down to a single item

libs/canvas/rect_set.cc

@@ -0,0 +1,134 @@
+/*
+ * Copyright (C) 2012 Carl Hetherington <carl@carlh.net>
+ * Copyright (C) 2013-2017 Paul Davis <paul@linuxaudiosystems.com>
+ * Copyright (C) 2015-2017 Robin Gareus <robin@gareus.org>
+ *
+ * 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 <cmath>
+
+#include "canvas/rect_set.h"
+
+using namespace std;
+using namespace ArdourCanvas;
+
+RectSet::RectSet (Canvas* c)
+	: Item (c)
+{
+
+}
+
+RectSet::RectSet (Item* parent)
+	: Item (parent)
+{
+
+}
+
+void
+RectSet::compute_bounding_box () const
+{
+	if (_rects.empty ()) {
+		_bounding_box = Rect ();
+	} else {
+		Rect rb;
+
+		for (auto const & r : _rects) {
+			rb = rb.extend (r);
+		}
+
+		_bounding_box = rb;
+	}
+
+	set_bbox_clean ();
+}
+
+void
+RectSet::render (Rect const & area, Cairo::RefPtr<Cairo::Context> context) const
+{
+	/* area is in window coordinates */
+
+	Rect p (parent()->item_to_window (parent()->bounding_box()).intersection (area));
+
+	for (auto const & r : _rects) {
+
+		Rect self;
+
+		self = item_to_window (r, false);
+		Rect intersection = self.intersection (p);
+
+		if (!intersection) {
+			continue;
+		}
+
+		Gtkmm2ext::set_source_rgba (context, r.color);
+
+		/* XXXX another example of where using COORD_MAX fails
+		 * (presumably at some point Cairo folds from double to an
+		 * integral and overflows). Use a "big number" that isn't too
+		 * big.
+		 *
+		 * We should really find out what the upper limit actually is
+		 * and use that for COORD_MAX.
+		 */
+
+		context->rectangle (intersection.x0, intersection.y0, intersection.width(), intersection.height());
+		context->fill ();
+	}
+}
+
+void
+RectSet::add_rect (int index, Rect const & ra, Gtkmm2ext::Color color)
+{
+	_rects.push_back (ColoredRectangle (index, ra, color));
+}
+
+void
+RectSet::begin_add ()
+{
+	begin_change ();
+}
+
+void
+RectSet::end_add ()
+{
+	set_bbox_dirty ();
+	end_change ();
+}
+
+void
+RectSet::clear ()
+{
+	begin_change ();
+	_rects.clear ();
+	set_bbox_dirty ();
+	end_change ();
+}
+
+bool
+RectSet::covers (Duple const & point) const
+{
+	if (bounding_box().contains (point)) {
+		return true;
+	}
+
+	for (auto const & r : _rects) {
+		if (r.contains (point)) {
+			return true;
+		}
+	}
+
+	return false;
+}