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ArdourCanvas::Line::covers() uses distance_to_segment_squared()

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This commit is contained in:
Paul Davis 2013-12-09 13:39:10 -05:00
parent 4780c84252
commit 77a63c2bf7
1 changed files with 37 additions and 8 deletions
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45
libs/canvas/line.cc
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@ -151,18 +151,47 @@ Line::set_y1 (Coord y1)
bool
Line::covers (Duple const & point) const
{
Duple p = canvas_to_item (point);
const Duple p = canvas_to_item (point);
static const Distance threshold = 2.0;
/* compute area of triangle computed by the two line points and the one
we are being asked about. If zero (within a given tolerance), the
points are co-linear and the argument is on the line.
/* this quick check works for vertical and horizontal lines, which are
* common.
*/
double area = fabs (_points[0].x * (_points[0].y - p.y)) +
(_points[1].x * (p.y - _points[0].y)) +
(p.x * (_points[0].y - _points[1].y));
if (_points[0].x == _points[1].x) {
/* line is vertical, just check x coordinate */
return fabs (_points[0].x - p.x) <= threshold;
}
if (area < 0.001) {
if (_points[0].y == _points[1].y) {
/* line is horizontal, just check y coordinate */
return fabs (_points[0].y - p.y) <= threshold;
}
Duple at;
double t;
Duple a (_points[0]);
Duple b (_points[1]);
const Rect visible (_canvas->visible_area());
/*
Clamp the line endpoints to the visible area of the canvas. If we do
not do this, we have a line segment extending to COORD_MAX and our
math goes wrong.
*/
a.x = min (a.x, visible.x1);
a.y = min (a.y, visible.y1);
b.x = min (b.x, visible.x1);
b.y = 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;
}