[Qt-creator] Custom widget not showing in Qt Designer on Linux

[Friedemann Kleint]

Hi,

here is an extract from the documentation we are planning to add to shed some 
light onto the Qt Designer plugin issue. I hope it helps:

"...You can use Qt APIs to create plugins that extend Qt Designer. Qt Designer 
fetches plugins from the standard locations and loads the plugins that match 
its build key. For more information on how to create and locate plugins and to 
change the default plugin path, see {How to Create Qt Plugins}.

Qt Designer is integrated into  Qt Creator and in addition comes as a 
standalone application. The correct folder to place the plugins depends on 
which you use. The integrated Qt Designer fetches plugins from the 
%SDK%\bin\designer folder on Windows and Linux and 
QtCreator.app/Contents/MacOS/designer folder on Mac. Choose Tools > Form 
Editor > About Qt Designer Plugins.

The standalone Qt Designer is part of the Qt library used for building 
projects, located under %SDK%/qt. Therefore, it fetches plugins from the 
following folder: %SDK%\qt\plugins\designer. To check which plugins where 
loaded successfully and which failed, choose Help > About Plugins in the Qt 
Creator.

The Qt Creator that is included in pre-built SDK packages on Windows is built 
with the Microsoft Visual Studio compiler, whereas the version of Qt shipped 
for building applications is configured and built to use the MinGW/g++ 
compiler. Plugins built by using this version of Qt cannot be loaded by Qt 
Creator because the build-keys do not match. The plugins can only be used in 
the standalone version of Qt Designer. Choose Help > About Qt Creator to check 
the Qt version Qt Creator was built with.

If you want to use Qt Designer plugins that were built for the shipped Qt 
version, you need to make sure that Qt Creator is built with the same compiler 
by either recompiling Qt Creator using MinGW or recompiling Qt with Microsoft 
Visual Studio, depending on which configuration you want to use for your 
applications."

Regards,
Friedemann
-- 
Friedemann Kleint
Nokia, Qt Development Frameworks