The QT program developed under win10 runs incorrectly on win7

[JonB]

@bergerac
While you wait for a specific solution from @hskoglund .

Whenever you get "no Qt platform plugin could be initialized", to diagnose set environment variable QT_DEBUG_PLUGINS=1 in a shell/terminal and then run your application. You should get a stream of diagnostic output. Look right near the end for whatever the cause of your final problem is.

[hskoglund]

Hi @bergerac most likely you successfully replaced Qt6Core.dll and Qt6Gui.dll but not qwindows.dll.
If you look in your C:\Qt\Tools\QtCreator\bin\plugins\platforms folder, the original qwindows.dll is from November 23, 2021 with a size of 780568 bytes.
My patched version is from December 21. 2021 with a size of 763904 bytes.

If you have the one from November that could explain the error "The application failed..."
Otherwise you can try following the advice from @JonB

[bergerac]

Hi @JonB @hskoglund
I checked the qwindows.dll again and confirmed that it had been replaced.
Then i use @JonB method to run QT creator.exe by cmd, but did not get any output report.Did I miss something?

[hskoglund]

To see the output you need to start DbgView

[JonB]

@hskoglund
Ah, I'm not a Windows Qt user. So it doesn't just output to stdout/err under Windows if run from a Command prompt?

[hskoglund]

@JonB No that would be too easy, but DbgView to the rescue.

[JonB]

@hskoglund
:) When I am advising people of this, do they have to download that DbgView, will it be there if they have MSVC or MinGW only?

[bergerac]

Hi @hskoglund @JonB
DbgView.exe shows the information
"[28200] qt.qpa.plugin: Could not load the Qt platform plugin "windows" in "" even though it was found.
[28200] This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem.
[28200] Available platform plugins are: direct2d, minimal, offscreen, windows."

[hskoglund]

@JonB Again, that would be too easy. One of the first things I do a new Windows PC is to download the complete SysInternals suite.

[hskoglund]

@bergerac Please include the text before "...[28200] qt.qpa.plugin: Could not load the Qt platform plugin "windows" in "" even though it was found.""

[JonB]

@bergerac
What did you do for

to diagnose set environment variable QT_DEBUG_PLUGINS=1 in a shell/terminal and then run your application.

because your output looks just like it was?

[bergerac]

Hi @hskoglund @JonB
@hskoglund There was nothing else before that information.
@JonB I open cmd, enter "set qt_debug_plugins = 1", and then locate to the installation directory to run QT Creator.exe.

[hskoglund]

Hi, the output should be a couple of thousand lines, the first one should be:

1  0.00000  [28200] QFactoryLoader::QFactoryLoader() checking directory path "C:/Qt/Tools/QtCreator/bin/plugins/platforms" ...

don't need all thousands of lines, just say the 40 at the end...

[JonB]

@bergerac
There ought be preceding output.

Try SET QT_DEBUG_PLUGINS=1, just in case capitals matter, though I suspect not under Windows, but don't know.

locate to the installation directory to run QT Creator.exe.

That is not what I said. I said run the executable, not Creator. It is not apparent to me the variable will necessarily be passed to the application when run from there. If you do it that way you should look inside Creator where you see the "runtime environment variables" set up. Which is why running the program directly from the Command prompt is simpler.

[bergerac]

Hi @JonB @hskoglund
I run QT creator.exe directly , and then can see the debugging information
"[28668] QFactoryLoader::QFactoryLoader() checking directory path "E:/Qt/Tools/QtCreator/bin/platforms" ...
[28668] Cannot load library E:\Qt\Tools\QtCreator\bin\plugins\platforms\qwindows--.dll: The specified program could not be found.
[28668] QLibraryPrivate::loadPlugin failed on "E:/Qt/Tools/QtCreator/bin/plugins/platforms/qwindows--.dll" : "Cannot load library E:\Qt\Tools\QtCreator\bin\plugins\platforms\qwindows--.dll: The specified program could not be found."
I renamed the old library as qwindows--.dll and put the new library in.Debugging information indicates that QT creator is still looking for old library when it runs.

[JonB]

@bergerac
Is you problem you reported earlier when you run Creator or when you run your application?
I think I had misunderstood, I thought it was your program, now I think it is Creator you cannot run, but it is not clear.

[bergerac]

Hi @JonB
My topic is the problem of running the developed application. Later, @hskoglund provided the modified Qt library and asked me to
build the development environment directly on win7 and develop application with QT creator. Therefore, the error later was the running error of Creator.
I'm sorry I didn't make it clear. Thank you again.

[JonB]

@bergerac I see. Then i must leave you in his hands for Qt6 issues.

[hskoglund]

Hi @bergerac sorry that it didn't work out as planned.

I think best solution is to install on older version of Qt Creator that uses Qt5, i.e. has no problems (and requires no patching :-) to run on your Windows 7.

A download of Qt Creator 5.0.3 you can find here (the first link).

When you start Qt Creator 5.0.3 the first time, a yellow box will be shown: "Link with a Qt installation to automatically register..." just click Yes (and I think you have to click Yes one more time). Then you can use that version of Qt Creator the normal way.

[bergerac]

Hi @hskoglund
I will follow your advice.
Thanks again for your help @JonB and @hskoglund