Yes thanks I know the maths for that, the problem being it's going to be
calculated for all lines every time the user touches the mouse.
Just to share here is my routine to calculate a QPointF distance to a
QLineF:
#define DIST(P1, P2) ((P1.x() - P2.x()) * (P1.x() - P2.x()) + (P1.y() -
P2.y()) * (P1.y() - P2.y()))
double Util::distToSegment(const QPointF &point,const QLineF &line)
{
const double d1 = DIST(line.p1(),line.p2());
if(d1 == 0.0)
return qSqrt(DIST(point, line.p1()));
const double t = ((point.x() - line.p1().x()) * (line.p2().x() -
line.p1().x())
+ (point.y() - line.p1().y()) * (line.p2().y() -
line.p1().y())) / d1;
if(t < 0)
return qSqrt(DIST(point, line.p1()));
if(t>1)
return qSqrt(DIST(point, line.p2()));
return qSqrt(DIST(point, QPointF(line.p1().x() + t * (line.p2().x()
- line.p1().x()),
line.p1().y() + t * (line.p2().y() -
line.p1().y()))));
}
I doubt there is a faster solution, still it's heavy if you need to do
that on each mouse move, for all lines/segments you need to iterate to
find the smallest.
Philippe Lelong
Le 07-03-2019 20:28, Jérôme Godbout a écrit :
Just throwing an idea, maybe you could convert the mouse click or
hover to coordinate on the Map::toCoordinate() and interpolate the
coordinate to see with parameter to the line vector and then find the
distance to that line parameter point or min/max point. This is not
super fast but could be quick enough. Maybe doing the inverted
converting the coordinate to point would make the computation easier.
http://mathworld.wolfram.com/Point-LineDistance2-Dimensional.html
-----Original Message-----
From: Interest <interest-boun...@qt-project.org> On Behalf Of maitai
Sent: March 7, 2019 12:33 PM
To: Interest@qt-project.org
Subject: [Interest] QtLocation MapPolyLine and MouseArea
Hi,
I need to trigger various actions whenever a MapPolyLine is hovered or
pressed, such as displaying a tooltip, a menu, etc.
I have put a MouseArea on it with anchors.fills: parent, but the
problem is that the mouse area does not represent the line, but the
polygon made by the line. For instance if you have a L shape, entered
event and so on is triggered when you enter the bounding rectangle of
the line, not when you hover over the line itself.
On a QGraphicsScene we had the shape() protected method for that kinds
of case, for instance with a QPainterPathStroker to give some
thickness to the line's "mousearea".
I will probably end with a custom property that will carry the pixel
distance between the line segments and the mouse coordinates, but this
is going to be heavy to compute (I have potentially hundreds of
complicated lines on the map).
Is there a better way or even better a standard way to do that?
Thanks
Philippe Lelong
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