Download along track doesn't completely download areas along the track

[GerdP]

What steps will reproduce the problem?

1. Load attached gpx file
2. Right click on layer and select "Download from OSM along this track"
3. Select 20m, 5 km² and track only in the popup
4. Click Download -> 9 should require individual download request
5. Click OK

What is the expected result?

The downloaded areas should completely cover the track

What happens instead?

Sometimes you see gaps, e.g. jump to

to see

Please provide any additional information below. Attach a screenshot if possible.

When I convert the gpx track to "data layer" and use "Download along way" from the download_along plugin the result looks correct.

Build-Date:2019-04-02 08:23:01
Revision:14953
Is-Local-Build:true

Identification: JOSM/1.5 (14953 SVN en) Windows 10 64-Bit
OS Build number: Windows 10 Home 1803 (17134)
Memory Usage: 529 MB / 1753 MB (392 MB allocated, but free)
Java version: 1.8.0_191-b12, Oracle Corporation, Java HotSpot(TM) 64-Bit Server VM
Screen: \Display0 1920x1080
Maximum Screen Size: 1920x1080
VM arguments: [-agentlib:jdwp=transport=dt_socket,suspend=y,address=localhost:55839, -Dfile.encoding=UTF-8]
Program arguments: [--debug]

Plugins:
+ FastDraw (34949)
+ OpeningHoursEditor (34867)
+ apache-commons (34506)
+ buildings_tools (34904)
+ continuosDownload (82)
+ download_along (34869)
+ ejml (34389)
+ geotools (34513)
+ jaxb (34678)
+ jts (34524)
+ o5m (34867)
+ opendata (34911)
+ pbf (34867)
+ poly (34867)
+ reltoolbox (34867)
+ reverter (34958)
+ undelete (34919)
+ utilsplugin2 (34932)

Last errors/warnings:
- W: No configuration settings found.  Using hardcoded default values for all pools.

[GerdP]

Although DownloadAlongTrackAction and DownloadAlongWayAction should do more or less the same the sources are very different.
The code in DownloadAlongWayAction provides the better solution using the private methods calcBetween()and calcScale().
I think it would be best to move all the code that calculates the areas into the base class DownloadAlongAction.

[GerdP]

Patch which duplicates code from DownloadAlongWayAction