Qt 5.15.5 cannot load custom designer plugin

TonyRietwyk

I have been using a custom designer plugin for many versions - most recently 5.12.7 on Windows 10. I've recently installed 5.15.5 downloaded from my Qt account and built the plugin using VS2019 32-bit. Designer starts OK, but the help / plugins shows the custom one failed to load. I have Qt5.15.5/5.15.5/msvc2019/bin in my system path. MS depends.exe takes a loooong time to load the DLL, and then shows very similar error messages to the linked topic. In particular API-MS-WIN-CORE-SYNCH-L1-2-0.DLL seems to be causing a cyclic dependency with KERNEL32.dll.

Does anyone know how to fix this? Does the installed Designer need 64-bit dll's? Is there an environment variable that I can set to get more information on why the load is failing? All of my other Qt apps seem to be building and working fine.

koahnig

@TonyRietwyk

Hi and welcome to open source devnet user forum

Certaily someone might be able to help you from this forum. However, Qt5.15.5 is not part of the open source and you have a paid customer account. Therefore, IMHO you shall contact customer support for help. At least it makes sense to contact them because you paid for the support.

TonyRietwyk

Turns out the problem was fixed by copying zlib1.dll into the 5.15.5\msvc2019\bin folder. Third-party QZStream component needs it. Sorry for the noise!

JKSH

@TonyRietwyk said in Qt 5.15.5 cannot load custom designer plugin:

Does the installed Designer need 64-bit dll's?

Designer or Creator? (Qt Creator has an embedded version of Qt Designer)

Recent releases of Qt Creator are 64-bit. You can check by clicking Help > About Qt Creator...

I'm not sure about the bitness of the stand-alone Qt Designer .

API-MS-WIN-CORE-SYNCH-L1-2-0.DLL seems to be causing a cyclic dependency with KERNEL32.dll.

The API-MS-*.dll are usually false positives. Ignore them.

I have Qt5.15.5/5.15.5/msvc2019/bin in my system path.

This often causes problems... I highly recommend you don't put Qt in your PATH. You can break other apps on your PC that depend on a different version of Qt.

@TonyRietwyk said in Qt 5.15.5 cannot load custom designer plugin:

Turns out the problem was fixed by copying zlib1.dll into the 5.15.5\msvc2019\bin folder

That should go into the folder which contains your plugin, not into your Qt folder.

Again, I recommend you remove Qt from your PATH.