Properly adding custom widget into Qt Designer

[Baltharos]

Hello,

I'm new to Qt, and I've been experimenting with a few things. I'm stuck with adding custom widgets to Qt Designer. I used the example given in Qt 5.3 (D:\Qt\Qt5.3.0\Examples\Qt-5.3\designer\customwidgetplugin), and ran it with release mode. Qt showed the 'find custom executable' dialogbox, which I think is fine (it's plugin anyway). Now, there are a few lines of command like:

TARGET = $$qtLibraryTarget($$TARGET)
 
target.path = $$[QT_INSTALL_PLUGINS]/designer
INSTALLS += target

TARGET = $$qtLibraryTarget($$TARGET)

target.path = $$[QT_INSTALL_PLUGINS]/designer
INSTALLS += target

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I can't find the DLL installed in any 'designer' folder on my installation directory. The custom widget doesn't show up on the left side on Designer either, or pops up when I try to promote a blank widget. When I tried to put the resulting DLL into D:\Qt\Qt5.3.0\Tools\QtCreator\bin\plugins\designer , the designer plugins dialogbox shows that the plugin failed because it used an incompatible library ([5.3.0] release).

Is there anything that I missed?

[wysota]

You need to build the plugin with the same compiler, Qt version and same mode (release) Creator was built with. This might not be the same version you are using for building your programs.

[Baltharos]

You need to build the plugin with the same compiler, Qt version and same mode (release) Creator was built with. This might not be the same version you are using for building your programs.

Yes, I have tried to check with this answer. The problem is, I have never installed another version of Qt before on my machine. Another computer (also installed with Qt 5.3.0 and definitely compiled with mingw) also has the same problem. I used the same source code without any alteration, ran qmake, ran it with release mode, and when I put the resulting .a and .dll files into the plugins/designer folder the same error popped out. The custom widget won't appear on QtCreator-integrated Designer or non-integrated Designer.
On the past documentations, I found a command - Q_EXPORT_PLUGIN2(), which is not in the customwidgetplugin source code example in 5.3. Is this actually required in this version?

[wysota]

As I said you need to build the plugin so that it is binary compatible with your Qt Creator which has its own Qt binaries. You can check the version from Creator's help menu.

Alternatively you can build Creator yourself from sources with the version of Qt you are using for your programs and then you will be able to use the plugin built with the same toolchain.

[Baltharos]

As I said you need to build the plugin so that it is binary compatible with your Qt Creator which has its own Qt binaries. You can check the version from Creator's help menu.

Alternatively you can build Creator yourself from sources with the version of Qt you are using for your programs and then you will be able to use the plugin built with the same toolchain.

The about window says "Qt Creator 3.1.1, based on Qt 5.2.1 (MSVC 2010) 32 bit". So I have to either compile the plugin again to Qt 5.2.1 & MSVC 2010, or compile my own Creator with that version?

[wysota]

Basically yes. It doesn't have to be Qt 5.2.1, it can be any of Qt 5.2.x, but it does have to be 32bit MSVC2010. If you decide to build Qt Creator yourself, you are free to choose any compiler and any supported Qt version.

[Baltharos]

Basically yes. It doesn't have to be Qt 5.2.1, it can be any of Qt 5.2.x, but it does have to be 32bit MSVC2010. If you decide to build Qt Creator yourself, you are free to choose any compiler and any supported Qt version.

Okay, thanks a lot! Also a question again (I'm sorry): I assume that to embed my own widgets/plugins to QtCreator/Designer I have to refer to the Creator build version, but if I want to add custom libraries/plugins to my applications using Qt 5.3 compiled with mingw, I have to build them with version 5.3 + mingw right?

[wysota]

but if I want to add custom libraries/plugins to my applications using Qt 5.3 compiled with mingw, I have to build them with version 5.3 + mingw right?

Yes, that's correct. Just bear in mind that if you split your plugin into two parts -- a library implementing the widget and a plugin itself that uses this library (be it statically or dynamically linked), you can link your application againt that library only.

[Baltharos]

Yes, that's correct. Just bear in mind that if you split your plugin into two parts -- a library implementing the widget and a plugin itself that uses this library (be it statically or dynamically linked), you can link your application againt that library only.

Okay, thanks a lot! It works now, although I have to use version 5.2.1 and version 5.3.0 together. Is it possible to use 5.3.2-compiled library/plugins in 5.3.0-compiled applications? I'm gonna try to shift to online installer (so I can use a single Creator), and the one offered is 5.3.2..

[wysota]

Is it possible to use 5.3.2-compiled library/plugins in 5.3.0-compiled applications?

It should be ok.

[Baltharos]

It should be ok.

Thanks a lot!