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livetrax/libs/canvas/poly_line.cc

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/*
Copyright (C) 2011-2013 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 "canvas/poly_line.h"
#include "canvas/canvas.h"
#include "canvas/utils.h"
using namespace ArdourCanvas;
PolyLine::PolyLine (Group* parent)
: Item (parent)
, PolyItem (parent)
{
}
void
PolyLine::render (Rect const & area, Cairo::RefPtr<Cairo::Context> context) const
{
if (_outline) {
setup_outline_context (context);
render_path (area, context);
context->stroke ();
}
}
bool
PolyLine::covers (Duple const & point) const
{
Duple p = canvas_to_item (point);
const Points::size_type npoints = _points.size();
if (npoints < 2) {
return false;
}
Points::size_type i;
Points::size_type j;
/* repeat for each line segment */
const Rect visible (_canvas->visible_area());
static const double threshold = 2.0;
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.
*/
a.x = std::min (a.x, visible.x1);
a.y = std::min (a.y, visible.y1);
b.x = std::min (b.x, visible.x1);
b.y = std::min (b.y, visible.y1);
double d = distance_to_segment_squared (p, a, b, t, at);
if (t < 0.0 || t > 1.0) {
return false;
}
if (d < threshold) {
return true;
}
}
return false;
}