add initial (untested) implementation of canvas ruler item

libs/canvas/canvas/ruler.h

@@ -0,0 +1,80 @@
+/*
+    Copyright (C) 2014 Paul Davis
+
+    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., 675 Mass Ave, Cambridge, MA 02139, USA.
+*/
+
+#ifndef __CANVAS_RULER_H__
+#define __CANVAS_RULER_H__
+
+#include <string>
+#include <vector>
+
+#include "canvas/item.h"
+#include "canvas/fill.h"
+#include "canvas/outline.h"
+
+namespace ArdourCanvas
+{
+	
+class LIBCANVAS_API Ruler : virtual public Item, public Fill, public Outline
+{
+public:
+	struct Mark {
+		enum Style {
+			Major,
+			Minor,
+			Micro
+		};
+		std::string label;
+		double position;
+		Style  style;
+	};
+	
+	struct Metric {
+		Metric () : units_per_pixel (0) {}
+		virtual ~Metric() {}
+
+		double units_per_pixel;
+
+		/* lower and upper and sample positions, which are also canvas coordinates
+		 */
+		
+		virtual int get_marks (std::vector<Mark>&, double lower, double upper, int maxchars) const = 0;
+	};
+	
+	Ruler (Group *, const Metric& m);
+	
+	void set_range (double lower, double upper);
+	void set_size (Rect const&);
+
+	void render (Rect const & area, Cairo::RefPtr<Cairo::Context>) const;
+	void compute_bounding_box () const;
+	
+private:
+	const Metric& _metric;
+	Rect          _rect;
+
+	/* lower and upper and sample positions, which are also canvas coordinates
+	 */
+
+	Coord         _lower;
+	Coord         _upper;
+};
+
+}
+
+
+#endif

libs/canvas/ruler.cc

@@ -0,0 +1,117 @@
+/*
+    Copyright (C) 2014 Paul Davis
+    Author: Carl Hetherington <cth@carlh.net>
+
+    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., 675 Mass Ave, Cambridge, MA 02139, USA.
+*/
+
+#include <algorithm>
+#include <cairomm/context.h>
+#include "pbd/compose.h"
+#include "canvas/ruler.h"
+#include "canvas/types.h"
+#include "canvas/debug.h"
+#include "canvas/utils.h"
+#include "canvas/canvas.h"
+
+using namespace std;
+using namespace ArdourCanvas;
+
+Ruler::Ruler (Group *p, const Metric& m)
+	: Item (p)
+	, Fill (p)
+	, Outline (p)
+	, _metric (m)
+{
+}
+
+void
+Ruler::set_range (double l, double u)
+{
+	_lower = l;
+	_upper = u;
+}
+
+void
+Ruler::set_size (Rect const & area)
+{
+	if (_rect != area) {
+		begin_visual_change ();
+		_rect = area;
+		_bounding_box_dirty = true;
+		end_visual_change ();
+	}
+}
+
+void
+Ruler::compute_bounding_box () const
+{
+	if (!_rect.empty()) {
+		_bounding_box = _rect;
+	}
+
+	_bounding_box_dirty = false;
+}
+
+void
+Ruler::render (Rect const & area, Cairo::RefPtr<Cairo::Context> cr) const
+{
+	Rect self (item_to_window (_rect));
+	boost::optional<Rect> i = self.intersection (area);
+	if (!i) {
+		return;
+	}
+
+	Rect intersection (i.get());
+
+	vector<Mark> marks;
+	Distance height = self.height();
+
+	_metric.get_marks (marks, _lower, _upper, 50);
+
+	/* draw background */
+
+	setup_fill_context (cr);
+	cr->rectangle (intersection.x0, intersection.y0, intersection.width(), intersection.height());
+	cr->fill ();
+
+	/* draw ticks */
+	
+	setup_outline_context (cr);
+
+	for (vector<Mark>::const_iterator m = marks.begin(); m != marks.end(); ++m) {
+		Duple pos;
+
+		pos.x = self.x0 + ((m->position - _lower) / _metric.units_per_pixel);
+		pos.y = self.y1; /* bottom edge */
+		
+		cr->move_to (pos.x, pos.y);
+		
+		switch (m->style) {
+		case Mark::Major:
+			cr->rel_move_to (0, -height);
+			break;
+		case Mark::Minor:
+			cr->rel_move_to (0, -(height/2.0));
+			break;
+		case Mark::Micro:
+			cr->rel_move_to (0, pos.y-(height/4.0));
+			break;
+		}
+		cr->stroke ();
+	}
+
+	/* done! */
+}