[Proj] PROJ 4.8.0, projects.h and projPJ struct

[Eric Miller]

I think that being able to interrogate the projection definition to know
if it has an inverse is useful, so a function should be added to
proj_api.h.

Perhaps:

int pj_has_inverse(projPJ);

And in pj_utils.c

/******************************************************************/
/*                                 pj_has_inverse()                    
            */
/*                                                                     
                   */
/*            Return TRUE if this coordinate system object has     */
/*            and inverse projection method.                           
  */
/*****************************************************************/
int pj_has_inverse( PJ *pj )
{
         return pj != NULL && pj->inv != NULL;
}

-- 

Eric G. Miller
Software Developer
CA Dept. of Fish & Game


>>> On 4/11/2012 at  3:30 AM, José Luis García Pallero
<jgpallero at gmail.com>
wrote:
> Hello:
> 
> As it is said in NEWS files from PROJ 4.8.0 now proj_api.h file
should
> be included in programs instead projects.h. I've tried to compile my
> old code (that has no problems with 4.7.0) and I've obtained a
warning
> and an error.
> In my code I have a declaration like
> 
> projPJ proyec;
> 
> and I use them later as
> 
> proyec = pj_init_plus(param);
> 
> and more later, in order to check if a projections has inverse step:
> 
> if(proyec->inv==0)
> {
> ......
> }
> 
> If I compile the program using 4.8.0 version I obtain a warning and
an 
> error:
> 
> geocproj.c:202:14: warning: dereferencing *void ** pointer
[enabled by
> default]
> geocproj.c:202:14: error: request for member *inv* in something
not a
> structure or union
> 
> Looking proj_api.h file, in both versions 4.7.0 and 4.8.0 I can see
the 
> block
> 
> for 4.7.0
> 
> #if !defined(PROJECTS_H)
>     typedef struct { double u, v; } projUV;
>     typedef void *projPJ;
>     #define projXY projUV
>     #define projLP projUV
> #else
>     typedef PJ *projPJ;
> #   define projXY	XY
> #   define projLP       LP
> #endif
> 
> for 4.8.0
> 
> #if !defined(PROJECTS_H)
>     typedef struct { double u, v; } projUV;
>     typedef void *projPJ;
>     #define projXY projUV
>     #define projLP projUV
>     typedef void *projCtx;
> #else
>     typedef PJ *projPJ;
>     typedef projCtx_t *projCtx;
> #   define projXY	XY
> #   define projLP       LP
> #endif
> 
> Both are the same (except for the ctx context). In both if
PROJECTS_H
> is not defined (i.e. if projects.h was not included) the type projPJ
> is defined as void* instead PJ*. PJ is defined in projects.h. But in
> the include/ folder of 4.8.0 project.h was not copied, so it's
> impossible to use it. So I can't use the 'inv' field and I suppone
no
> PJ struct at all as projPJ was defined as void*. Then which is the
> correct way in order to use the new PROJ 4.8.0 version?
> 
> 
> 
> On the other hand, suppose that 4.8.0 works well in my case only
> including proj_api.h. Then my problem is that if I have not
knowledge
> about the version of PROJ in one computer, how can I proceed in
order
> to use the correct include depending versions.
> First of all, can I use version 4.7.0 (for example) with only
> #include<proj_api.h>? In my case the answer is NO because I obtain
the
> same warning and error that in 4.8.0. Then I try:
> 
> #include<proj_api.h>
> #if PJ_VERSION<480
> #include<projects.h>
> #endif
> 
> PJ_VERSION is defined in proj_api.h. I check if version is older
than
> 4.8.0 and try to include then projects.h. But I obtain some errors:
> 
> /usr/include/projects.h:139:33: error: conflicting types for
*projUV*
> /usr/include/proj_api.h:54:37: note: previous declaration of
*projUV*
> was here
> geocproj.c: In function *ProjFwd*:
> geocproj.c:120:9: error: incompatible type for argument 1 of
*pj_fwd*
> /usr/include/proj_api.h:66:8: note: expected *projUV* but
argument is
> of type *projUV*
> geocproj.c: In function *ProjInv*:
> geocproj.c:202:14: warning: dereferencing *void ** pointer
[enabled by
> default]
> geocproj.c:202:14: error: request for member *inv* in something
not a
> structure or union
> geocproj.c:223:9: error: incompatible type for argument 1 of
*pj_inv*
> /usr/include/proj_api.h:67:8: note: expected *projUV* but
argument is
> of type *projUV*
> 
> We can see conflicting type errors due to definitions of projUV in
> proj_api.h and projects.h.
> 
> Opinions about?
> 
> Cheers