ardour/libs/canvas/poly_line.cc

/*
 * Copyright (C) 2012 Carl Hetherington <carl@carlh.net>
 * Copyright (C) 2013-2017 Paul Davis <paul@linuxaudiosystems.com>
 * Copyright (C) 2015-2016 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 <algorithm>

#include "canvas/canvas.h"
#include "canvas/poly_line.h"
#include "canvas/utils.h"

using namespace ArdourCanvas;

PolyLine::PolyLine (Canvas* c)
	: PolyItem (c)
	, _threshold (1.0)
	, _y1 (0)
{
}

PolyLine::PolyLine (Item* parent)
	: PolyItem (parent)
	, _threshold (1.0)
	, _y1 (0)
{
}

void
PolyLine::compute_bounding_box () const
{
	PolyItem::compute_bounding_box ();
	if (_y1 > 0 && _bounding_box) {
		_bounding_box.x0 = 0;
		_bounding_box.x1 = COORD_MAX;
		if (_y1 > _bounding_box.y1) {
			_bounding_box.y1 = _y1;
		}
	}
}

void
PolyLine::set_fill_y1 (double y1)
{
	begin_change ();
	set_bbox_dirty ();
	_y1                 = y1;
	end_change ();
}

void
PolyLine::render (Rect const& area, Cairo::RefPtr<Cairo::Context> context) const
{
	if (_fill && _y1 > 0 && _points.size () > 0) {
		const ArdourCanvas::Rect& vp (_canvas->visible_area ());
		setup_fill_context (context);

		Duple y (0, _y1);
		float y1 = item_to_window (y).y;
		render_path (area, context);
		Duple const& c0 (left_edge ());
		Duple const& c1 (right_edge ());
		if (c1.x < vp.x1) {
			context->line_to (vp.x1, c1.y);
			context->line_to (vp.x1, y1);
		} else {
			context->line_to (vp.x1, y1);
		}
		if (c0.x > vp.x0) {
			context->line_to (vp.x0, y1);
			context->line_to (vp.x0, c0.y);
		} else {
			context->line_to (vp.x0, y1);
		}
		context->close_path ();
		context->fill ();
	}

	if (_outline) {
		setup_outline_context (context);
		render_path (area, context);
		context->stroke ();
	}
}

void
PolyLine::set_steps (Points const& points, bool stepped)
{
	if (!stepped) {
		PolyItem::set (points);
		return;
	}

	Points copy;
	for (Points::const_iterator p = points.begin (); p != points.end ();) {
		Points::const_iterator next = p;
		++next;

		copy.push_back (*p);
		if (next != points.end () && next->x != p->x) {
			copy.push_back (Duple (next->x, p->y));
		}

		p = next;
	}

	PolyItem::set (copy);
}

// Clamp x1 to xmax, and scale y1 accordingly, relative to (x0,y0)
static void
clamp2 (double& x1, double& y1, double x0, double y0, double xmax) {
	if (x1 > xmax) {
		double dx = x1 - x0;
		double dy = y1 - y0;
		double slope = 0;
		// only compute slope if relevant (and safe without overflow / division by zero);
		// the line is on the xmax edge, and barely visible since x1 is far out and dx is small
		if (fabs(dx) > 0.1) {
			slope = dy / dx;
		}
		x1 = xmax;
		double new_dx = x1 - x0;
		y1 = y0 + new_dx * slope;
	}
}

bool
PolyLine::covers (Duple const& point) const
{
	Duple p = window_to_item (point);

	const Points::size_type npoints = _points.size ();

	if (npoints < 2) {
		return false;
	}

	Points::size_type i;
	Points::size_type j;

	double squared_threshold = _threshold + _outline_width;
	squared_threshold *= squared_threshold;

	/* repeat for each line segment */

	const Rect visible (window_to_item (_canvas->visible_area ()));

	for (i = 1, j = 0; i < npoints; ++i, ++j) {
		Duple  at;
		double t;
		Duple  a (_points[j]);
		Duple  b (_points[i]);

		/*
		  Clamp the line endpoints to the visible area of the canvas. If we do
		  not do this, we may have a line segment extending to COORD_MAX and our
		  math goes wrong.
		*/

		clamp2 (a.x, a.y, b.x, b.y, visible.x1);
		clamp2 (a.y, a.x, b.y, b.x, visible.y1);
		clamp2 (b.x, b.y, a.x, a.y, visible.x1);
		clamp2 (b.y, b.x, a.y, a.x, visible.y1);

		double d = distance_to_segment_squared (p, a, b, t, at);

		if (t < 0.0 || t > 1.0) {
			continue;
		}

		if (d < squared_threshold) {
			return true;
		}
	}

	return false;
}

void
PolyLine::set_covers_threshold (double t)
{
	_threshold = t;
}