[Qgis-developer] More towgs84 for a single EPSG

[Radim Blazek]

I would like to add new codes for Krovak/S-JTSK CRS (EPSG 5514,
5221...) especialy because users do not see those codes in WMS/WFS
dialogs. The problem is that those CRS are used in different countries
with different towgs84 params (EPSG 4836, 5239).

It seems that QGIS is not able to manage multiple different towgs84
params for the same EPSG. Current situation:
 - system tbl_srs has UNIQUE INDEX idx_srsauthid on tbl_srs(auth_name,auth_id)
 - GUI for user tbl_srs does not allow to set auth_name nor auth_id
(but it would be ignored anyway)
 - QgsCoordinateReferenceSystem - seems that authid
(auth_name:auth_id) is widely used as a unique identifier, it just
substituted former epsg:
     - used (a lot, also to store CRS in settings): authid(),
createFromOgcWmsCrs()
     - not used setAuthId()
     - not used and deprecated: createFromEpsg(), epsg(), setEpsg()

In theory we could add new 'EPSG' codes for them, but it is not good
solution because:
 - such codes would not be offered to user in WMS/WFS CRS change
dialog (and thus it does not solve the original problem)
 - possible conflicts with other projects

There is a similar ticket for 3003 and 3004 codes:
http://hub.qgis.org/issues/2332

Any ideas how to solve this problem?

Radim