SlippyMapTileViewer - permission problem with temporary directories

[dl8dtl]

JOSM apparently creates temporary directories where it wants to store
private data. These directories have a system-wide name, so the first
user within a system to run JOSM creates them. Subsequently, when a
different user runs JOSM, it fails to use these directories:

Failed to save ETag: /var/tmp/JMapViewerTiles/Mapnik/13_4329_2539.etag (Permission denied)
Failed to save ETag: /var/tmp/JMapViewerTiles/Mapnik/13_4329_2538.etag (Permission denied)
Failed to save ETag: /var/tmp/JMapViewerTiles/Mapnik/13_4330_2539.etag (Permission denied)
Failed to save ETag: /var/tmp/JMapViewerTiles/Mapnik/13_4330_2538.etag (Permission denied)
Failed to save tile content: /var/tmp/JMapViewerTiles/Mapnik/13_4329_2538.png (Permission denied)
Failed to save tile content: /var/tmp/JMapViewerTiles/Mapnik/13_4329_2539.png (Permission denied)
Failed to save tile content: /var/tmp/JMapViewerTiles/Mapnik/13_4330_2538.png (Permission denied)
Failed to save tile content: /var/tmp/JMapViewerTiles/Mapnik/13_4330_2539.png (Permission denied)

[stoecker]

This is a problem of the SlippyMapChooser tile viewer code which is not directly part of JOSM.

[jpstotz]

I changed the default path where JMapViewer places it's tile disk cache: added user name.
Hence on Linux the default temp path changes to

/tmp/JMapViewerTiles_$username$