[Qgis-developer] Module dependencies

[Vincent Picavet]

Hello,

Le mardi 23 septembre 2014 12:35:41, Régis Haubourg a écrit :
> Hi all,
> I didn't mention the option to port Mem Layer saver to core for two
> reasons: 
> - that doesn't solve the proble of general plugin dependencies

Actually the general plugin dependencies problem is a distribution problem, 
and should not be solved inside QGIS. We really do not want to reimplement a 
multi-platform package management software.

As stated before, auto-installing packages should also be done with great 
care, which is as well why package management software exist in the first 
place.

There are a few possibilities to improve the current situation :
* Make it clear for the user that additional packages are needed for a plugin, 
and show him a page explaining how to install them, according to its platform.

* Have a stricter policy on plugins regarding external dependencies (e.g. do 
not accept plugins in official repo which have dependencies on packages not 
included in osgeo4w, or default qgis binaries)

* Have these dependency informations available in the plugin's metadata

* Have a better plugin architecture, which makes it easier to deal with 
dependencies, using tools made for that purpose (i.e. make qgis plugins real 
python packages installable with pip install).

I think the main point is first to warn the user and guide him for further 
install steps, instead of getting python "import failed" errors.

> - we already discussed how to port Mem Layer Saver to core on list, and
> ended up to the conclusion that we needed to modify qgs format from a xml
> text file to a zip container of project properties + datas + resources
> (symbols svg for instance)
> 
> Porting that plugin to core is allright to me, but we will make qgis the
> only soft to write data files along data project file, with high risks of
> data loss (because user will forget it or trash it). Do we really want it?
> 
> + to port, only if we clearly understand the impacts. I would prefer a new
> qgs format.

Porting the new memory layer feature + promping the user to save unsaved 
memory layers when closing the project would already be a first step, without 
the need for data storage in qgis project file.

Vincent