Leftover segment after breaking track generation by right-click

[JFritzle]

Describe the bug

Generating a track segment from A to B may take some time, e.g. long distant hiking segment.
When breaking router's segment calculation by right-click, we notice two cases:

• the usual and normal one:
  • latest clicked track endpoint B gets discarded
  • no track segment from A to B is drawn
  • starting point of a new track segment becomes again green marked starting point A
• the rare unexpected one:
  • latest clicked track endpoint B gets discarded
  • track segment from A to B is already drawn into map because segment calculation has finished during right-click
  • starting point of a new track segment becomes again green marked starting point A
  • leftover segment keeps visible until a new track segment gets generated or track generation gets aborted

What have you done to circle down the problem?

To Reproduce

1. Generate a long distant and time consuming track segment from point A to point B
2. Break track segment generation almost simultaneously when router's track segment calculation to point B finishes
3. You may notice that point B gets discarded although track segment from A to B is already calculated and drawn
4. If not, repeat steps 1 and 2

Expected behavior

Either: Point B does not get discarded if track segment from A to B is already drawn.
Or: If point B gets discarded, leftover already drawn track segment from A to B gets withdrawn from map.

Screenshots

Green marked point on the left has been starting point A and became again starting point A after breaking track segment generation by right-click while segment to endpoint B is already calculated and drawn:

Notice: Track distance in Track Metrics box is 0.0 m, which is the correct distance from A to A.

Attachments

Tracebacks

Desktop

• OS: any
• QMapShack Version: dev version
• Window Manager: -

Additional context

[JFritzle]

I can not decide, but perhaps it is the same or a similar race condition:

To generate track, points marked by digits 1 to 6 have been left-clicked.
While point 5 has not been marked by black square as waypoint although left-clicked, point ? is being marked as waypoint although not left-clicked.

[kiozen]

Imho if we really want to fix that properly we need to find out what's happening in the code. The real root cause. If that is 100% understood a fix is probably easy. So far I failed to understand it properly.