[Qgis-developer] --with-wfs switch

[Tom Elwertowski]

Hi Marco,

>> When building --with-wtf, wfsplugin fails on a Mac when linking. When I
>> remove ../../providers/wfs/libwfsprovider.la from wfsplugin_la_LIBADD,
>> the plugin then links and loads.
> 
> And does the wfs plugin work? My expectation is that connect (GetCapabilities) 
> will fail.
> 

It crashes when the connect is done. Some of the other plugins fail to 
load if needed routines cannot be found so I incorrectly assumed that if 
it loaded, it must have resolved all symbols.


>> On a Mac, a plugin cannot be linked to another plugin. On Ubuntu, there
>> is a warning message that linking wfsplugin against libwfsprovider is
>> not portable.
> 
> Is this a limitation inherent to the Mac platform? If yes, I have to change 
> the plugin and provider a bit.
> The WFS plugin is linked to the WFS provider. This is because of the 
> GetCapabilities request which is implemented as static method 
> QgsWFSProvider::GetCapabilities.
> I think i will just move the GetCapabilities method from the provider to the 
> plugin. I would then also move QgsHttpTransaction to the qgis core library 
> because it is used from wms provider, wfs provider and wfs plugin.

It appears to be a limitation for straight-forward cross-platform code 
and makefiles. It might be possible to do something using 
platform-specific link flags. I don't know.

When I looked at this a year ago for grass, partitioning the grass 
provider into two pieces was an understandable and finite task whereas 
learning the link flags was open-ended with no guarantee for success. 
(The grass provider now contains only the provider API, provider.cpp. 
The other provider files moved to libqgisgrass which is shared by both 
provider and plugin.)

It looks like a Linux plugin has the same capabilities as a library 
while a Mac plugin is a lightweight leaf module that cannot function as 
a library.

Since libtool says using a plugin as a library is non-portable, I am 
trusting the libtool developers who know far more about link flags than 
I do.

Tom