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Wed Nov 22 04:40:48 2017

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Auxiliary Storage support in QGIS 3

For those who know how powerful QGIS can be using data defined widgets and expressions almost anywhere in styling and labeling settings, it remains today quite complex to store custom data.

For instance, moving a simple label using the label toolbar is not straightforward, that wonderful toolbar remains desperately greyed-out for manual labeling tweaks

…unless you do the following:

  • Set your vector layer editable (yes, it’s not possible with readonly data)
  • Add two columns in your data
  • Link the X property position to a column and the Y position to another

 

the Move Label map tool becomes available and ready to be used (while your layer is editable). Then, if you move a label, the underlying data is modified to store the position. But what happened if you want to fully use the Change Label map tool (color, size, style, and so on)?

 

Well… You just have to add a new column for each property you want to manage. No need to tell you that it’s not very convenient to use or even impossible when your data administrator has set your data in readonly mode…

A plugin, made some years ago named EasyCustomLabeling was made to address that issue. But it kept being full of caveats, like a dependency to another plugin (Memory layer saver) for persistence, or a full copy of the layer to label inside a memory layer which indeed led to loose synchronisation with the source layer.

Two years ago, the French Agence de l’eau Adour Garonne (a water basin agency) and the Ministry in charge of Ecology asked Oslandia to think out QGIS Enhancement proposals to port that plugin into QGIS core, among a few other things like labeling connectors or curved labels enhancements.

Those QEPs were accepted and we could work on the real implementation, so here we are, Auxiliary storage has now landed in master!

How

The aim of auxiliary storage is to propose a more integrated solution to manage these data defined properties :

  • Easy to use (one click)
  • Transparent for the user (map tools always available by default when labeling is activated)
  • Do not update the underlying data (it should work even when the layer is not editable)
  • Keep in sync with the datasource (as much as possible)
  • Store this data along or inside the project file

As said above, thanks to the Auxiliary Storage mechanism, map tools like Move Label, Rotate Label or Change Label are available by default. Then, when the user select the map tool to move a label and click for the first time on the map, a simple question is asked allowing to select a primary key :

Primary key choice dialog – (YES, you NEED a primary key for any data management)

From that moment on, a hidden table is transparently created to store all data defined values (positions, rotations, …) and joined to the original layer thanks to the primary key previously selected. When you move a label, the corresponding property is automatically created in the auxiliary layer. This way, the original data is not modified but only the joined auxiliary layer!

A new tab has been added in vector layer properties to manage the Auxiliary Storage mechanism. You can retrieve, clean up, export or create new properties from there :

Where the auxiliary data is really saved between projects?

We end up in using a light SQLite database which, by default, is just 8 Ko! When you save your project with the usual extension .qgs, the SQLite database is saved at the same location but with a different extension : .qgd.

Two thoughts with that choice: 

  • “Hey, I would like to store geometries, why no spatialite instead? “

Good point. We tried that at start in fact. But spatialite database initializing process using QGIS spatialite provider was found too long, really long. And a raw spatialite table weight about 4 Mo, because of the huge spatial reference system table, the numerous spatial functions and metadata tables. We chose to fall back onto using sqlite through OGR provider and it proved to be fast and stable enough. If some day, we achieve in merging spatialite provider and GDAL-OGR spatialite provider, with options to only create necessary SRS and functions, that would open news possibilities, like storing spatial auxiliary data.

  • “Does that mean that when you want to move/share a QGIS project, you have to manually manage these 2 files to keep them in the same location?!”

True, and dangerous isn’t it? Users often forgot auxiliary files with EasyCustomLabeling plugin.  Hence, we created a new format allowing to zip several files : .qgz.  Using that format, the SQLite database project.qgd and the regular project.qgs file will be embedded in a single project.zip file. WIN!!

Changing the project file format so that it can embed, data, fonts, svg was a long standing feature. So now we have a format available for self hosted QGIS project. Plugins like offline editing, Qconsolidate and other similar that aim at making it easy to export a portable GIS database could take profit of that new storage container.

Now, some work remains to add labeling connectors capabilities,  allow user to draw labeling paths by hand. If you’re interested in making this happen, please contact us!

 

 

More information

A full video showing auxiliary storage capabilities:

 

QEP: https://github.com/qgis/QGIS-Enhancement-Proposals/issues/27

PR New Zip format: https://github.com/qgis/QGIS/pull/4845

PR Editable Joined layers: https://github.com/qgis/QGIS/pull/4913

PR Auxiliary Storage: https://github.com/qgis/QGIS/pull/5086

Increasing the stability of processing algorithms

Processing just got a new testing framework to improve the long-term stability of this important plugin. And you can help to improve it, even if you are not a software developer! This is yet another piece in our never-stopping crusade to

Passing android Intents to Qt

Working on QField I had the necessity of passing values from the QtActivity.java to the Qt cpp world, here how I did it using an Intent that is sent to the QtActivity (the one you should not edit that comes with

QGIS Crowdfunding: 2.5D Rendering

2.5D rendering

Build and deploy c++ QGIS custom application on windows

After a lot of troubles, I managed to compile and deploy a QGIS c++ app on windows. This small guide will describe the steps I followed. This has been tested on win xp and windows 7, both in 32 bits.

Development environment

Your app must be built using MSVC 9.0 (2008) since QGIS in OSGeo’s package was built with it. Hence, MinGW cannot be used.

  1. Install Microsoft Visual Studio Express 2008.
  2. Install QGIS and Qt libs using OSGeo4W installer
  3. Install Qt Creator
  4. If you want a debugger,you should install CDB. This can be achieved by installing Windows SDK environment. In the installation process, only select Debugging toos for windows.

I wasn’t able to use the compiler yet, so I am not 100% sure about 4.

Now, if you want to build using Qt Creator, it must be started in a proper environment. Adapt this batch to launch Qt Creator:

ECHO Setting up QGIS DEV ENV

set PYTHONPATH=

set OSGEO4W_ROOT=C:\OSGeo4W
call "%OSGEO4W_ROOT%\bin\o4w_env.bat"

@set QMAKESPEC=win32-msvc2008
@set PATH=%OSGEO4W_ROOT%\bin;%OSGEO4W_ROOT%\apps\qgis-dev\bin;%PATH%

@set INCLUDE=%INCLUDE%;%OSGEO4W_ROOT%\include;%OSGEO4W_ROOT%\apps\qgis-dev\include
@set LIB=%LIB%;%OSGEO4W_ROOT%\lib;%OSGEO4W_ROOT%\apps\qgis-dev\lib

path %OSGEO4W_ROOT%\bin;%SYSTEMROOT%\System32;%SYSTEMROOT%;%SYSTEMROOT%\System32\wbem;C:\Progra~1\Git\bin;C:\Qt\qtcreator-3.0.1\bin;%PATH%

set VS90COMNTOOLS=C:\Program Files\Microsoft Visual Studio 9.0\Common7\Tools\
call "C:\Program Files\Microsoft Visual Studio 9.0\VC\vcvarsall.bat" x86

start "Qt Creator" /B C:\Qt\qtcreator-3.0.1\bin\qtcreator.exe %*

Then, you need to configure a proper kit in Qt Creator.

  1. Go to Options -> Build & Run -> Compilers and check that Microsoft Visual C++ Compiler 9.0 is correctly detected.
  2. Then in Qt Versions tab, add Qt from the OSGeO installation, normally c:\OSGeo4W\bin\qmake.exe
  3. In Debuggers tab, add cdb.exe found in c:\Debugging tools for windows\ 
  4. Finally, check in Kits that it is properly configured.

Building the application

This is what looks like an application project file.

QT += core gui xml
greaterThan(QT_MAJOR_VERSION, 4): QT += widgets
TARGET = hfp
TEMPLATE = app
SOURCES += YOURSOURCES
HEADERS +=YOUR HEADERS
FORMS += YOUR FORMS
RESOURCES += images/images.qrc

win32:CONFIG(Release, Debug|Release) {
 LIBS += -L"C:/OSGeo4W/lib/" -lQtCore4
 LIBS += -L"C:/OSGeo4W/lib/" -lQtGui4
 LIBS += -L"C:/OSGeo4W/lib/" -lQtXml4
 LIBS += -L"C:/OSGeo4W/apps/qgis-dev/lib/" -lqgis_core
 LIBS += -L"C:/OSGeo4W/apps/qgis-dev/lib/" -lqgis_gui
}
else:win32:CONFIG(Debug, Debug|Release) {
 PRE_TARGETDEPS += C:/OSGeo4W/lib/QtCored4.lib
 PRE_TARGETDEPS += C:/OSGeo4W/lib/QtGuid4.lib
 PRE_TARGETDEPS += C:/OSGeo4W/lib/QtXmld4.lib
 LIBS += -L"C:/OSGeo4W/lib/" -lQtCored4
 LIBS += -L"C:/OSGeo4W/lib/" -lQtGuid4
 LIBS += -L"C:/OSGeo4W/lib/" -lQtXmld4
 LIBS += -L"C:/OSGeo4W/apps/qgis-dev/lib/" -lqgis_core
 LIBS += -L"C:/OSGeo4W/apps/qgis-dev/lib/" -lqgis_gui
}
win32:{
 INCLUDEPATH += C:/OSGeo4W/include
 DEPENDPATH += C:/OSGeo4W/include
 INCLUDEPATH += C:/OSGeo4W/apps/qgis-dev/include
 DEPENDPATH += C:/OSGeo4W/apps/qgis-dev/include
 DEFINES += GUI_EXPORT=__declspec(dllimport) CORE_EXPORT=__declspec(dllimport)
}
unix {
 LIBS += -L/usr/local/lib/ -lqgis_core -lqgis_gui
 LIBS += -L/usr/local/lib/qgis/plugins/ -lgdalprovider
 INCLUDEPATH += /usr/local/include/qgis
 DEFINES += GUI_EXPORT= CORE_EXPORT=
}

Remarks

  • GUI_EXPORT and CORE_EXPORT must be set to __declspec(dllimport). I don’t know exactly what it means, but I found out reading this thread, with some hazardous tries. If you don’t set these, you won’t be able to call any variable defined as extern in QGIS (e.g. cursors).
  • Qt release libraries shall not be mixed up with debug config in your project. In other words, use release libs for release mode and debug libs for debug mode.

With this, you should be able to compile your QGIS application in Qt Creator!

You can find some coding examples on github which are a bit old but still useful to start.

Now, to get the whole potential of QGIS libs, you must initialize the QgsApplication in your main window class:

#if defined(Q_WS_WIN)
  QString pluginPath = "c:\\OSGeo4W\\apps\\qgis-dev\\plugins";
  QString prefixPath = "c:\\OSGeo4W\\apps\\qgis-dev\\";
#else
  QString pluginPath = "/usr/local/lib/qgis/plugins/";
  QString prefixPath = "/usr/local";
#endif

  QgsApplication::setPluginPath( pluginPath );
  QgsApplication::setPrefixPath( prefixPath, true);
  QgsApplication::initQgis();

Deploying on windows

Since QGIS is not to be installed on the target computer, the built app will not be able to find the path declared in previous code.
There is probably a better approach, but here is a way to solve this:
Change the path to

  QString pluginPath = "c:\\myapp\\qgis\plugins";
  QString prefixPath = "c:\\myapp\\qgis";

This means you must deploy the app to this exact location: c:\myapp. In this directory, you need to create a qgis folder in which you will copy c:\OSGeo4W\apps\qgis-dev\resources and c:\OSGeo4W\apps\qgis-dev\plugins.

Besides, this you will need to copy some DLLs to be able to run the applications. You might want to use the dependency walker to find which are needed.

The batch file hereafter creates a folder on the building machine that will contain all the needed files in my case (it might be different in your case).

rmdir c:\myapp /Q /S
mkdir c:\myapp
mkdir c:\myapp\iconengines
mkdir c:\myapp\qgis
mkdir c:\myapp\qgis\resources
mkdir c:\myapp\qgis\plugins

copy PATHTOMYAPP\build-myapp-Desktop-Release\release\myapp.exe c:\myapp\
copy c:\OSGeo4W\bin\QtCore4.dll c:\myapp\
copy c:\OSGeo4W\bin\QtGui4.dll c:\myapp\
copy c:\OSGeo4W\bin\QtXml4.dll c:\myapp\
copy c:\OSGeo4W\bin\QtNetwork4.dll c:\myapp\
copy c:\OSGeo4W\bin\QtSvg4.dll c:\myapp\
copy c:\OSGeo4W\bin\QtWebKit4.dll c:\myapp\

copy c:\OSGeo4W\bin\zlib_osgeo.dll c:\myapp\
copy c:\OSGeo4W\bin\msvcr71.dll c:\myapp\
copy c:\OSGeo4W\bin\phonon4.dll c:\myapp\
copy c:\OSGeo4W\bin\proj.dll c:\myapp\
copy c:\OSGeo4W\bin\geos_c.dll c:\myapp\
copy c:\OSGeo4W\bin\gdal110.dll c:\myapp\
copy c:\OSGeo4W\bin\ogdi_32b1.dll c:\myapp\
copy c:\OSGeo4W\bin\libexpat.dll c:\myapp\
copy c:\OSGeo4W\bin\xerces-c_3_1.dll c:\myapp\
copy c:\OSGeo4W\bin\LIBPQ.dll c:\myapp\
copy c:\OSGeo4W\bin\SSLEAY32.dll c:\myapp\
copy c:\OSGeo4W\bin\LIBEAY32.dll c:\myapp\
copy c:\OSGeo4W\bin\krb5_32.dll c:\myapp\
copy c:\OSGeo4W\bin\comerr32.dll c:\myapp\
copy c:\OSGeo4W\bin\k5sprt32.dll c:\myapp\
copy c:\OSGeo4W\bin\gssapi32.dll c:\myapp\
copy c:\OSGeo4W\bin\hdf_fw.dll c:\myapp\
copy c:\OSGeo4W\bin\mfhdf_fw.dll c:\myapp\
copy c:\OSGeo4W\bin\jpeg_osgeo.dll c:\myapp\
copy c:\OSGeo4W\bin\jpeg12_osgeo.dll c:\myapp\
copy c:\OSGeo4W\bin\netcdf.dll c:\myapp\
copy c:\OSGeo4W\bin\geotiff.dll c:\myapp\
copy c:\OSGeo4W\bin\libtiff.dll c:\myapp\
copy c:\OSGeo4W\bin\sqlite3.dll c:\myapp\
copy c:\OSGeo4W\bin\spatialite4.dll c:\myapp\
copy c:\OSGeo4W\bin\freexl.dll c:\myapp\
copy c:\OSGeo4W\bin\iconv.dll c:\myapp\
copy c:\OSGeo4W\bin\libxml2.dll c:\myapp\
copy c:\OSGeo4W\bin\LIBMYSQL.dll c:\myapp\
copy c:\OSGeo4W\bin\hdf5.dll c:\myapp\
copy c:\OSGeo4W\bin\szip.dll c:\myapp\
copy c:\OSGeo4W\bin\libcurl.dll c:\myapp\
copy c:\OSGeo4W\bin\zlib1.dll c:\myapp\
copy c:\OSGeo4W\bin\openjp2.dll c:\myapp\
copy c:\OSGeo4W\bin\spatialindex1.dll c:\myapp\
copy c:\OSGeo4W\bin\qwt5.dll c:\myapp\

copy c:\OSGeo4W\apps\qt4\plugins\iconengines\qsvgicon4.dll c:\myapp\iconengines\

copy C:\Progra~1\Git\bin\libiconv-2.dll c:\myapp\
copy C:\Progra~1\Git\bin\libintl-8.dll c:\myapp\

copy c:\OSGeo4W\apps\qgis-dev\bin\qgis_Core.dll c:\myapp\
copy c:\OSGeo4W\apps\qgis-dev\bin\qgis_gui.dll c:\myapp\
copy c:\OSGeo4W\apps\qgis-dev\bin\msvcp90.dll c:\myapp\

copy c:\windows\system32\msvcp100.dll c:\myapp\
copy c:\windows\system32\msvcr100.dll c:\myapp\

copy C:\OSGeo4W\apps\qgis-dev\resources\* c:\myapp\qgis\resources
copy C:\OSGeo4W\apps\qgis-dev\plugins\* c:\myapp\qgis\plugins

To be able to run the app, on a fresh windows XP, I had to install:

And copy the whole folder c:\myapp from the building machine to the target machine.

It seems that from Vista, the 2005 redistributable package is included. So, no need to install it.

And voilà!


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