My 5 cent of Olivers suggestion:

A possible use and implementation case could be:

Use case I:
- Read the track into QMS
- Create 1 to n waypoints near the track for possible new track start
points
- The waypoints will be recognized internally as "assigned track
waypoints" within a threshold of 50m
- Maybe rename the waypoints by proper names

Implementation:
- Development of a new track filter "Reassign start point", maybe in
the section "Miscellaneous"
- GUI could be very simple: One Combobox with the list of the names of
the assigned track waypoints and the "Compute" pushbutton
- The track vector of the given points has internally be reordered from
"n" to "end point" from "end point" "to start point" from "start point"
to "n"

Use Case II:
- Select an assigned track waypoint from Combobox list and push the
button of "Compute"
- Then track points will be reordered beginning with the selected track
waypoint

Still to be consider:
- Implementation will be consider "all" kind of tracks, a non circle
track will be then linked from end to start point, may be a long
straight line from end to start point will be the shown
- Tracks with internal multiple segments will be transformed to one
internal segment
- How to handle history (I am not experienced in that)?
- Timestamps of the track points has maybe reassign by a new starting
date and time (has to reflect a bit more in detail)

Hope it helps.

Karl ...


Am Dienstag, den 13.03.2018, 19:08 +0100 schrieb Oliver Eichler:
> Ah, ok I recall the stuff. 
> 
> 
> I do not know of a library to read GPX files written in C or C++. In
> the first 
> place you need an XML parser and writer. There are libraries for that
> task. Qt 
> has one, too. That's what I use in QMS. 
> 
> Of course you can extract the code from QMS. But the GPX and track
> classes and 
> their sub-classes are quite some beasts. After all tracks are
> incredible 
> complex GIS items. 
> 
> So you might end up like Karl, writing your own track filter in QMS.
> By that 
> you can focus on the task without dealing too much with GPX, drawing
> stuff 
> etc..
> 
> 
> Oliver
> 
> 
> 
> 
> 
> Am Dienstag, 13. März 2018, 14:07:43 CET schrieben Sie:
> > 
> > -------- Weitergeleitete Nachricht --------
> > Betreff:    Fwd: Re: [Qlandkartegt-users] Shift the Startpoint
> > from a
> > track to another point; Programming an own tool
> > Datum:      Tue, 13 Mar 2018 14:03:35 +0100
> > Von:        APM <apschwim...@apmland.de>
> > An:         Qmapshack mailing list <qlandkartegt-users@lists.source
> > forge.net>
> > 
> > 
> > 
> > Note: I got a SMTP error for my first mail, second try.
> > 
> > Hi Oliver,
> > 
> > 
> > yes of course!
> > 
> > We mainly use circle hiking paths, the tracks are given. The track
> > starts and end at the same point.
> > 
> > But from time to time we start and finish at another point on the
> > circle.
> > 
> > Problem: If I use my Garmin  GPS with this track, the "journey-
> > computer"
> > (in German menue 'Reisecomputer') shows me the remaining distance
> > and
> > time to the end of the track, which is not the endpoint we really
> > have
> > and the remaining distance and time are 'wrong'.
> > 
> > My idea is to manipulate the track in this way, that I define a new
> > startpoint and the c++ programm change the trackpoints in
> > accordance to
> > the new startpoint.
> > 
> > So far as I know, the Garmin GPS can't do a shift of a startpoint
> > from a
> > track.
> > 
> > 
> > Kind regards
> > 
> > 
> > Axel
> > 
> > Am 13.03.2018 um 12:57 schrieb Oliver Eichler:
> > > 
> > > Can you explain again what you want to do? It sounds like moving
> > > trackpoints without changing the timestamp or other properties.
> > > 
> > > Oliver
> > > 
> > > > 
> > > > Gesendet: Dienstag, 13. März 2018 um 10:09 Uhr
> > > > Von: APM <apschwim...@apmland.de>
> > > > An: "Qmapshack mailing list" <qlandkartegt-users@lists.sourcefo
> > > > rge.net>
> > > > Betreff: [Qlandkartegt-users] Shift the Startpoint from a track
> > > > to
> > > > another point; Programming an own tool
> > > > 
> > > > Dear all,
> > > > 
> > > > for a couple of month I asked in this list how to shift a
> > > > startpoint
> > > > from a given track without to cut and assemble the track.
> > > > 
> > > > It's a pity, but I have no solution until now or do not
> > > > understand what
> > > > to do in this case.
> > > > 
> > > > My idea is to progamm a tool in C++ of my own, but I'm
> > > > inexperienced.
> > > > 
> > > > My question is, if there's a class in the libary I can use  or
> > > > maybe a
> > > > similar tool is already present?
> > > > 
> > > > 
> > > > Thank you very much!
> > > > 
> > > > 
> > > > Kind regards
> > > > 
> > > > 
> > > > Axel
> > > > 
> > > > 
> > > > 
> > > > 
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