From 77a63c2bf75d4c8fa6948981a246806453bef95c Mon Sep 17 00:00:00 2001 From: Paul Davis Date: Mon, 9 Dec 2013 13:39:10 -0500 Subject: [PATCH] ArdourCanvas::Line::covers() uses distance_to_segment_squared() --- libs/canvas/line.cc | 45 +++++++++++++++++++++++++++++++++++++-------- 1 file changed, 37 insertions(+), 8 deletions(-) diff --git a/libs/canvas/line.cc b/libs/canvas/line.cc index fcc190a705..61acf89252 100644 --- a/libs/canvas/line.cc +++ b/libs/canvas/line.cc @@ -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. + */ + + if (_points[0].x == _points[1].x) { + /* line is vertical, just check x coordinate */ + return fabs (_points[0].x - p.x) <= threshold; + } + + 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. */ - 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)); + 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); - if (area < 0.001) { + 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; }