[Qgis-developer] Build plugins for use with Mac binary

Peter Ersts ersts at amnh.org
Thu Jan 22 14:51:25 EST 2009

QGIS can deal ok with third party plugins, but there is room for 
improvement. However, my problems are largely a mac specific packaging 
issue, i.e., I can't easily link to the shared libraries that are being 
distributed with the application.

Nonetheless I have found a solution (which I don't think is acceptable 
but it works). I took all of the libs out of the 
__app/Contents/MacOS/lib and placed then in my development directory ( 
/Users/pete/devel/libhack), then using install_name_tool changed all of 
the @executable_path/lib/ to /Users/pete/devel/libhack. Then I compiled 
my plugin and linked to the hacked libs, which works just fine because 
they are after all shared libs, the problem is that the linker can't 
deal with the @exe.. reference.


William Kyngesburye wrote:
> PS. Something occurred to me about distributing a plugin binary - Qgis 
> isn't properly setup for 3rd-party plugins. This requires (on OSX, but 
> not necessarily other platforms):
> - an external plugin dir, like in the user's home folder. It's not a 
> good idea to install 3rd-party plugins inside an application's bundle 
> on OSX. I don't know if Qgis has this option, but it's dependent on 
> the next requirement.
> - it can handle an arbitrary location for the Qgis application. Users 
> can and will move and/or rename the Qgis application.
> This relocation flexibility has a couple parts:
> - the plugin is compiled with the -bundle flag, which is true now
> - the plugin does NOT reference any library inside the Qgis 
> application package. And there's the problem. Normally, the -bundle 
> flag gets around the problem of linking the main binary of a program 
> (qgis) because that binary is assumed to be loaded already, but Qgis 
> plugins also link the Qgis *libraries* and the Qt frameworks.
> I'm not sure if the -bundle flag works for secondary linked libraries 
> (ie qgiscore as linked from qgis), but I think it should. It would be 
> worth trying to compile your plugin by linking only GEOS and GDAL, no 
> qgis or Qt, something like:
> -bundle -undefined dynamic_lookup -framework GEOS -framework GDAL
> This would also solve the problem of the incorrect library versions in 
> the all-in-one build.
> Heck, if we figure that qgis also loads the GEOS and GDAL libraries, 
> you could also leave those out, then there wouldn't be the GEOS 
> version problem. You just have to assume that builds of Qgis will use 
> the same GEOS and GDAL major versions, which could be dangerous.
> (The safe way would be to compile separate plugin binaries for each 
> Qgis distro.)
> On Jan 21, 2009, at 2:25 PM, William Kyngesburye wrote:
>> But really, it shouldn't matter what Qgis itself uses for extra 
>> dependencies - external libraries or frameworks, or bundled. And it's 
>> not really up to Qgis to provide these itself (bundled).
>> You can make your plugin with whatever dependencies you like, 
>> independent of what Qgis uses. You just need to make sure that they 
>> are available somehow, either packaged with the plugin (or linked as 
>> static libraries, which is good for oddball libraries), or in Qgis 
>> (not recommended, except for Qt and Qgis libraries) or separately 
>> (like my frameworks).
>> Just build the plugin, ie with my frameworks, and don't change those 
>> references, just the Qgis and Qt references. Though there is 
>> something wrong in the all-in-one build with the Qgis library 
>> versions, which should be fixed for it to work at all.
> -----
> William Kyngesburye <kyngchaos*at*kyngchaos*dot*com>
> http://www.kyngchaos.com/
> "We are at war with them. Neither in hatred nor revenge and with no 
> particular pleasure I shall kill every ___ I can until the war is 
> over. That is my duty."
> "Don't you even hate 'em?"
> "What good would it do if I did? If all the many millions of people of 
> the allied nations devoted an entire year exclusively to hating the 
> ____ it wouldn't kill one ___ nor shorten the war one day."
> <Ha, ha> "And it might give 'em all stomach ulcers."
> - Tarzan, on war

Peter J. Ersts, Project Specialist
American Museum of Natural History
Center for Biodiversity and Conservation
Central Park West at 79th Street
New York, New York 10024
Tel: Home Office (518)-632-4745 or NYC Office (212)-496-3488
Web: http://biodiversityinformatics.amnh.org
Web: http://cbc.amnh.org

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