[Qt-creator] designer plugins

[Uwe Rathmann]

Hi all,

I have to confess, that I don't use the creator myself much, but as 
maintainer of the Qwt library ( http://qwt.sf.net ) I have to deal with a 
lot of frustration concerning being unable to load the Qwt designer plugin 
in the creator - especially on Windows.

So finally I set up a Windows system and tried myself, to find out what 
the reasons are why so many fail:

1) 
Probably the most important one is, that the designer plugin needs to be 
compiled with the same Qt version and compiler version as the Creator - 
what is often a different one, than the combination the user wants to 
build his application with.

Surprisingly I had to note, that even the Creator inside the MinGW binary 
package of Qt comes with its own libs - incompatible to the libs of the 
package.

2)
Qwt users are often engineers or students not always experienced software 
developers. Setting environment variables seems to be a problem. 

Unfortunately I couldn't find a way how to tell the creator where to look 
for plugins beside setting QT_PLUGIN_PATH - or copying the plugin into 
the default directories of creator and designer.

3) 
When loading the designer plugin, the creator also needs to find the Qwt 
library itself. As it is not possible to compile the install path into 
the plugin ( rpath ) on Windows the PATH variable needs to be configured.

--

What I can and will do on my side is to modify the Qwt makefiles to 
compile the Qwt libs statically into the plugin ( to avoid 3) and to 
offer precompiled versions of the Qwt designer plugin that are compatible 
with the current binary packages of the Creator ( to improve 1) ).

On the Creator side I can imagine 3 things to be helpful:

a) 
The information in "About Creator" could be extended to show all relevant 
information, so that a user can identify how a plugin needs to be 
compiled: f.e MinGW vs. MSVC is missing.

b) 
When the plugin has been compiled properly, but I didn't do 3), the 
creator is able to show the information, that the plugin has been found, 
but loading it failed. For all other issues the plugin was silently 
ignored.

Maybe it is possible to improve the diagnostics about why a plugin was 
not loaded - even the simple information that a DLL has been neglected 
without further information is better than nothing.

c)
To avoid 2) it would be nice if the Creator makes it possible to edit a 
search path for where to look for plugins in its user interface. Maybe it 
is even possible to configure versions of the Creator individually - like 
it can be done with the path where to look for feature files with "qmake -
set QMAKEFEATURES ...".

Uwe