[SoC] [pgrouting-dev] [pgRouting] GSoC 2018 Final Report :Making pgRoutingLayer plugin compatible with the new version of QGIS and add GUI support for proposed functions.

Aasheesh Tiwari aasheesht50 at gmail.com
Mon Aug 13 18:06:24 PDT 2018

Making pgRoutingLayer plugin compatible with the new version of QGIS and
add GUI support for proposed functions.
Google Summer of Code 2018

   - Author - Aasheesh Tiwari
   - Mentor 1 - Cayetano Benavent
   - Mentor 2 - Vicky Vergara <https://wiki.osgeo.org/wiki/User:Cvvergara>
   - Organization - OSGeo <http://www.osgeo.org/>, pgRouting
   - Developer Community - pgRouting-dev


pgRoutingLayer is a plugin for QGIS that serves as a GUI for pgRouting
which is a popular routing solution for PostGIS database. The plugin is
written in python . It uses SIP to create python bindings for C/C++
libraries, pycopg2 for interacting with PostGreSQL. Internally
pgRoutingLayer uses pgRouting to provide geospatial routing functionality.
of pgRoutingLayer

A python plugin for QGIS must have the following files:

*init_.py* : The starting point of the plugin . It has the classFactory()
method which makes it known to QGIS . It receives iface (instance of
QgisInterface) which is used to interact with QGIS environment.*init*.py
returns an instance of our plugin. It also has other initialisation code.

*metadata.txt* : It contains general info , version, name and some other
metadata used by plugin’s website and plugin infrastructure.

*UI file* : It stores the user interface configuration for ther plugin,
saved in a XML format. It contains definitions of Qt widgets with slots and
signals. There are two ways to use this file , one is to include the file
with the app and render and parse it directly at runtime using uic . The
other way is to compile the file into python classes and include it in the
python source files. pgRoutingLayer plugin uses the first approach.

*Resource file* : It contains the resources needed by the plugin like
icons,translation file etc. It is an XML based file that lists files on
disk and assigns them a resource name that the application must use to
access the resource.

*pgRoutinLayer.py* : It contains the python code that actually defines the
functionality of the plugin. The pgRoutingLayer plugin breaks the large
code of main.py into modules that are manageable and easy to understand .
Below diagrams introduces the names of files and their dependency.

[image: screen shot 2018-08-13 at 2 09 49 am]
before GSoC 2018:

In 2018 QGIS released QGIS 3.0 which introduced an API break for existing
plugins including pgRoutinLayer.The key changes in QGIS 3.0 are as follows:

   - Updated from Qt4 to Qt5
   - Updated from PyQt4 to PyQt5
   - Updated from Python 2.7 to Python 3.0
   - QGIS API is improved , many classes have been deprecated or renamed.

The above changes have implications that the pgRoutingLayer plugin is no
longer compatible with QGIS 3.0 . The aim of this project was to make the
pgRoutingLayer plugin compatible with the new version of QGIS. Another
objective was to add functionalities for the proposed functions which are
to be released with the next mayor release.
of plugin in QGIS 3.0 before GSoC 2018

[image: screen shot 2018-08-13 at 6 24 17 am]
through this project:

As can be seen above there were 4 major issues which needed to be addressed
in order to make the plugin compatible. I followed the below tasks :

   1. Ported the plugin from python 2.7 to python 3 . For this, python
   future library was used. No library can give perfect result, so after that
   manually made corrections to the code which the library had wrongly ported.
   2. For making Qt4 to Qt5 conversion, changed all the renamed classes,
   removed all deprecated classes and replaced them with new equivalent
   classes, made changes according to the new classes.
   3. For PyQt4 to PyQt5, the same above process was done.
   4. Major part of the code uses QGIS API which was changed. So the task
   was to use the new QGIS classes in the code. QGIS community has released
   'QGIS API break' document which contains all the changes made in the new
   API. So changes to the code were done by following the API break document.
   This was the most crucial part and also the most time taking part. For
   every removed class, I had to find an equivalent class and make changes in
   the code for new class. For every renamed class, needed to change all the
   code with new class name.

The above 4 steps were refined again and again until the code worked.

The second part of the project involved making the plugin ready for the
next major release of pgRouting. First removed all the functions which are
going to be deprecated. Next task was to make changes in the plugin to
accept new parameters for the upcoming functions. So GUI changes were made.
Now code was written for new functions which involved sql queries and
drawing the output. Due to time constraints only 2 functions could be
coded. These functions were unstable so I merged the code into a new
branch. Finally documentation for the code and unit test for some files has
been written. The final status of plugin is that it works in QGIS 3.0 There
are some funtions like pgr_Ksp which needs improvement.
Status of Plugin in QGIS 3.xx : Works Perfectly !!

[image: screen shot 2018-08-13 at 6 42 32 am]

pgRouting has a vast collection of stable functions(probably made by
previous GSoC students). These functions need to be present in
pgRoutingLayer plugin so that QGIS users can be benefitted. For this we
need to add more functionality to the plugin. This is a task on it's own so
it may be a potential topic for GSoC 2019.
see some examples

Link to presentation
to project's OSGeo wiki:

to project code:

   - pgRoutingLayer compatible with QGIS 3.0
   - pgRoutingLayer with Added Functionality

to commit history

All the changes made by me during GSoC 2018 can be followed through the
below link, which directs to commit history. Commit history

   - Tsp function gives the output but it is not rendering.
   - Ksp function needs improvement.
   - Trsp works fine but they are complex to use and tooltips are not well

Best Regards,
*Aasheesh Tiwari*
*MTech | CSRE*
*Indian Institute Of Technology Bombay*
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