Linking C++ and JS with PYTHON

involving QGIS C++ APIs, PyQGIS, QWebKit and PyQt

Case study: Geosisma a QGIS plugin


Work committed by: Faunalia (www.faunalia.eu)

Who am I

15 year working on Spatial Ground Segments
Landsat, Cryosat, MODIS, Sentinel...

Since 2006 in QGIS/GRASS

QGIS Core developer
WMS Legend support in legend and composer
Saving style in Spatialite
Add SVG support to Mapserver/SLD interface
Bug fixing
Plugin porting and developing

Founder of GFOSS.it
Italian OSGEO Local Chapter

Co-Author of Mastering QGIS
















Reviewer for

QGIS Python Programming Cookbook
















QGIS (mainly C++)

QT  (C++)
http://qt-project.org/

SIP (Python2C++/C binder)

What is QGIS


Geographic Information System

What is Geosisma


Online/Offline Earthquake Damage Inventory Tool

Offline Functional Specifications 

  • Cache preparing integrating other project code

  • Download "Requests" based on User Credentials using REST APIs

  • Fill "Safety report" with "Request" data

  • Associate Cadastral Polygon to "Safety report"

  • Edit Cadastral Polygons

  • The same  Online behavior (zooming, auto-complete, data validation)  

  • Upload "Safety reports" and cadastral poligons using public REST APIs



I'm a lazy developer


reuse, reuse, reuse,  reuse,  reuse,  reuse,  reuse          

What About HTML5?


Main usable feature for Geosisma Offline


  • Caching (Offline capability)

  • Persistence (Session and Local storage)

  • Platform Independent


Re-use Online Form


  • Created using Django
  • Complex specification (Form validation and logic)
  • Re-using final form rendering
  • Minimal modifications
  • Follow evolution (next will be mobile)

....SO....

Insert the Online form inside QGIS

...Brighton 10th QGIS Hackfest...


"first" (secret) prototype

tech available since 2011

QgisD3 by Luca Casagrande


credits: Anita Graser: http://www.flickr.com/photos/48244569@N02/9930490423/in/pool-2286344@N25/

QgisD3 Python Plugin

a never published plugin

The architecture

Container

  • Instantiate WebView

  • Configure WebView (QWebSettings)

  • Instantiate Bridge class

  • (optional) add listener to Bridges's events

  • Inject Bridge in JS (addToJavaScriptWindowObject)

  • inject JS code to evaluate (eg. a JS bridge methods - evaluateJavaScript)


WebView2Container Bridge


  • Def PY slots called by JS
        @pyqtSlot(<params definition>)
        def slotName(self, records):

  • (optional) define out signals - pyqtSignal()



WebView (JS)


sourcing JS bridge (Container2WebView bridge)

Results

Luigi Pirelli

luipir@gmail.com - @ginetto



Work committed by: Faunalia (www.faunalia.eu)
Licence: (CC BY-SA 3.0)

QGIS: Linking C++ and JS with Python

By Luigi Pirelli

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QGIS: Linking C++ and JS with Python

"Geosisma offline" is QGIS plugin in which Python is used to link QGIS(c++) with web technologies (JS). Main tech used involve C++, Qt, PyQT, SIP, PyQGIS and QWebKit

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