[Proj] Getting Proj information after pj_init has been thrown

Frank Warmerdam warmerdam at pobox.com
Mon Jan 5 12:45:13 EST 2009

Gerald I. Evenden wrote:
> On Monday 05 January 2009 11:27:21 am Frank Warmerdam wrote:
>> Till wrote:
>>> Hi all and a very happy new year to anyone.
> 	...
>> Generally speaking internal access to the PJ structure is not encouraged.
> I guess I do not understand this statement as I ask: why?
> One should not alter the contents but examination is encouraged.  That is why 
> there is the -V option in program lproj.  The stucture is the "definition" of 
> the projection operation.  It is the digested result of all the "+args" that 
> have been thrown at the initialization.


I have not considered the PJ structure public as PROJ.4 has evolved.  The
internals are not exposed when using the proj_api.h public include file.
The contents of the structure are not well documented.

Amoung other things, I try to avoid ABI changes in PROJ.4 as much as possible,
but if apps can access the PJ structure contents that makes it part of the ABI
and thus hard to extend without disruption.

None of this prevents a developer from using the contents of the structure
if they want to, but they do so at their own risk and having to work out some
of the details on their own.

Best regards,
I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | Geospatial Programmer for Rent

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