[SOLVED]Failed to load platform plugin "windows"

hskoglund

Hi your Qt version of mingw48_32 is 5.2.1 and your Qt version of msvc2012_opengl is 5.3.

Copying files from these releases together in one folder is alright, problem arises for the subfolders, in this case the platforms subfolder.

I'm guessing the files in there comes from the 5.2.1 version of Qt, and when qwindows.dll requests a Qt5xxx.dll it will fail because all the Qt5xxx.dlls are from the 5.3 version of Qt. Hence the "plugin" error.

EDIT: what I mean, the main problem is mixup of mingw48_32 and msvc2012 compiler technology, i.e. for a single .exe, it cannot both use .dlls from ming48_32 compiler and msvc2012_compiler.

abraker95

The only DLL's I copied from the mingw48_32 folder is the platform since it's the only qWindows.dll I found. The rest of the DLL's come from the msvc2012_opengl folder and the QtCreator's bin folder (such as libEGL.dll).

hskoglund

Hmmm, I also have msvc2012_opengl installed and it has a qwindows.dll for sure.

Also, never copy anything from QtCreator's bin folder, because QtCreator for Qt version 5.3 is built with msvc2010 and Qt version 5.2.1. Best is to think about QtCreator's bin folder as private.

abraker95

Then where do I copy libEGL.dll from? Many people claim it to have solved the platform error.

EDIT: libGLESv2.dll is also located there. The application requests that DLL and it is not located within the msvc2012_opengl's bin folder.

hskoglund

libEGL.dll and libGLESv2.dll are not needed for the msvc2012_opengl compiler.

If you want, you can read more about this in my "blog post":http://www.tripleboot.org/?p=138 scroll down to "msvc2012_opengl".

abraker95

Regardless, I still have the same error even after following your blog post (I posted a comment regarding that on your blog some time earlier).

abraker95

In your blog you write,
"This deployment is almost the same as the non-OpenGL versions above, but actually easier since there is no libEGL.dll and libGLESv2.dll dependencies."

Yet I get this when using msvc2012_opengl with no libGLESv2.dll in the directory of the file:
!http://i62.tinypic.com/10424w0.jpg(compile)!

abraker95

Update:

I reinstalled Qt and corrected all the kit's compilers and Qt's. Using Microsoft Visual C++ Compiler 12.0 (x86) and Qt 5.3.0 (msvc2013) I was able to solve the error. However now the program crashes when run. While it runs within Qt, it still shows a crash error in the application output:

"The instruction at 0x5b175f0d referenced memory at 0x00000000. The memory could not be read.
Click on OK to terminate the program"

Edit: Qt shows this:
"QWindowsWindow::setGeometry: Unable to set geometry 75x23+480+190 on QWidgetWindow/'QPushButtonClassWindow'. Resulting geometry: 124x23+480+190 (frame: 8, 31, 8, 8, custom margin: 0, 0, 0, 0, minimum size: 0x0, maximum size: 16777215x16777215).
Problem creating accessible interface for: QPushButton(0x88fd18)
Make sure to deploy Qt with accessibility plugins."

EDIT 2:
After adding the "Accessible" folder from the plugins directory the program works fine in Qt. It still crashes when not running from Qt, however.

EDIT 3:
I rebuilt the debug version of the application and it still shows the platform error. I have no idea why the debug and release versions are showing different results.

JKSH

[quote author="abraker95" date="1402618312"]And no it doesn’t work in Qt.[/quote]If it doesn't work in Qt Creator, then it won't work when you try to deploy it. You need to get it to work in Qt Creator first.

By the way, "Qt" is the name of the library. "Qt Creator" is the name of the IDE that uses the Qt library.

[quote author="abraker95" date="1402618312"]The only DLL’s I copied from the mingw48_32 folder is the platform since it’s the only qWindows.dll I found. The rest of the DLL’s come from the msvc2012_opengl folder...[/quote]You must not mix DLLs. Only take from the folder that matches your compiler. DLLs that don't match your compiler will break your program.

[quote author="abraker95" date="1402618312"]Yet I get this when using msvc2012_opengl with no libGLESv2.dll in the directory of the file[/quote]I'm guessing this happened because you copied the MinGW DLLs (which DO need libEGL.dll/libGLESv2.dll), and Qt tried to load the non-OpenGL DLLs. Like I said before, don't mix.

[quote author="abraker95" date="1402618312"]Qt shows this:
“QWindowsWindow::setGeometry: Unable to set geometry 75×23+480+190 on QWidgetWindow/‘QPushButtonClassWindow’. Resulting geometry: 124×23+480+190 (frame: 8, 31, 8, 8, custom margin: 0, 0, 0, 0, minimum size: 0×0, maximum size: 16777215×16777215).[/quote]This message is safe and doesn't cause crashes. It appeared because you didn't specify a size for the QPushButton.

[quote]Problem creating accessible interface for: QPushButton(0×88fd18)
Make sure to deploy Qt with accessibility plugins.”[/quote]This message is safe and doesn't cause crashes. It won't stop your program from running.

Anyway, I recommend:

Uninstall the versions of Qt that you don't need. Only keep the one that matches your compiler.

Remove Qt from your PATH (if you put it there before)

Remove MinGW from your PATH (if you put it there before)

Delete the build-Hello_World-Desktop-Release folder

Start a new project using the Qt Creator wizard: File -> New File or Project... -> Applications -> Qt Widgets Application

JKSH

[quote author="abraker95" date="1402618312"]
EDIT 2:
After adding the "Accessible" folder from the plugins directory the program works fine in Qt. It still crashes when not running from Qt, however.[/quote]That doesn't sound right. If you click the "Run" button, Qt Creator will find the DLLs automatically. You shouldn't need to copy anything.

Where did you copy the folder into?

After you follow the steps in my previous post, please post a screenshot of Tools -> Options -> Build & Run -> Kits

abraker95

I copied the folder to where the application is.

Here:
!http://i59.tinypic.com/xgigj9.jpg(Kit)!

hskoglund

Hi, I see on your computer, MinGW and Visual Studio are both installed, this will invariably lead to problems. I think, if you want to have 2 different compilers, you need to have 2 different computers.

JKSH

@abraker95: I'm surprised that you don't have anything auto-detected. How did you install Qt? What packages did you download?

[quote author="hskoglund" date="1402630458"]Hi, I see on your computer, MinGW and Visual Studio are both installed, this will invariably lead to problems. I think, if you want to have 2 different compilers, you need to have 2 different computers. [/quote]That in itself isn't an issue. I have Qt for both MinGW and MSVC 2013 on my computer; they can coexist just fine.

However, abraker95 has done manual configuration for his kits, so they might not have been set up correctly. That why I recommended removing Qt and MinGW from the PATH, and uninstalling unneeded copies.

abraker95

I finally got both the debug and release versions of the applications working from Qt and from the folders when the appropriate DLL's are copied. However, as you have said, Qt doesn't want to auto-detect anything.

These are the environment variables I found relating to Qt in the projects tab on the left:
PATH: C:\Qt\5.3\msvc2013\bin
QTDIR: C:\Qt\5.3\msvc2013

I found no environment variables relating to MingW (I do have it installed, though). More confusing, why doesn't the application run from Qt when clearly the path to the Qt version is set without the copied DLL's?

abraker95

I finally solved that problem too!
Thank this thread: "Fix":http://qt-project.org/forums/viewthread/29372

So to get the application to be run from Qt without copying DLL's over, you will have to add an environment variable to the project's settings. Note that I'm using msvc2013 in this example, so replace that with what you are using. Here are the baby steps on doing this:

Head over to the projects tab on the left
On the top you will see the kit(s) you are using to build the project with. Click on run (which is right next to "build"). This will bring you to a similar, yet a little different page.
Scroll down until you see Run Environment
Click on details on the right to expand the section
Click on the add button on right
Type or Copy/Paste QT_QPA_PLATFORM_PLUGIN_PATH as the variable name on the lest column.
In the right column, type in the directory in which you platform is in. In my case, it is "C:\Qt\5.3\msvc2013\plugins\platforms".
Run the project

Edit: For step 7, "$(QTDIR)\plugins\platforms" should be able to automatically point to the needed directory. Thank this thread: "link":http://qt-project.org/forums/viewthread/26001

If you are getting any errors relating to DLL's or something like so:
"The instruction at 0×5b175f0d referenced memory at 0×00000000. The memory could not be read.
Click on OK to terminate the program"
Then you probably don't have an environment variable pointing to the bin directory of the compiler you are using.

I wish the process would have been simpler. hskoglund, perhaps you might include this in your blog as well?

hskoglund

Hi, it's in "my blog":http://www.tripleboot.org/?p=536 (scroll down to bonus contents) but I had a spelling error: -QT_QPA_PLUGIN_PATH- fixed now.

Good it worked for you, but using QT_ QPA_PLATFORM_PLUGIN_PATH I think has 2 disadvantages:

If your app depends on other plugins/subdirectories, for example imageformats or sqldrivers, then this environment variable has no effect
if you deploy your app to another computer then you must remember to set the environment variable on that computer as well.

abraker95

I wonder why the IDE doesn't set the platform directory by default.

hskoglund

It does when you install Qt, the installer writes the plugin path into Qt5Core.dll and qmake.exe.

frankiefrank

hskoglund - that last comment really helped me out! I was changing Qt versions, copied my DLLs (including Qt5Cored.dll) to the deployment target location. After a while I needed to reinstall the Qt version and I didn't have a clue why it wouldn't work - until I read your comment about the installer's change.

silviutp

I have also had headakes with my app which worked in Qt Creator and on my computer but not on other computer.
The problem was that I was not using the correct qwindows.dll. I used the version from P:\Qt\Qt5.1.1-mingw\Tools\QtCreator\bin\plugins\platforms.
The correct version is in P:\Qt\Qt5.1.1-mingw\5.1.1\mingw48_32\plugins\platforms
As hskoglund said, you should'n probably use dlls from qtcreator folder.