Application failed to start because it could not find or load the QT platform plugin "windows"

Question

I have looked through all of the questions that appear to be related on stack overflow, and none of the solutions seem to help me.

I am building a Qt application with this setup:

• Windows 7 Professional x64
• Visual Studio 2012
• Qt 5.2.0 built with configure -developer-build -debug-and-release -opensource -nomake examples -nomake tests -platform win32-msvc2012 -no-opengl
• Project uses QtSingleApplication (qt-solutions)
• Application is a 32 bit application
• qmake run with the following: -makefile -spec win32-msvc2012
• .pri uses QMAKE_CXX += /D_USING_V110_SDK71_

I can build and run my program fine on my development machine (noted above); I can also install and run the package from Program Files directory on dev machine.

When I install and run on a Windows Vista machine (multiple machines)

• VC++ redist 2012 11.0.61030.0 installed
• VC++ redist 2010 10.0.40219 installed
• plus 2005, 2008 versions of redist

(also fails on a clean install of Windows 7)

I get:

Application failed to start because it could not find or load the QT platform plugin "windows"

So I followed the instructions and added a .platforms/ directory, and added qwindows.dll (also added qminimal.dll and qoffscreen.dll); I also added libEGL.dll, libGLESv2.dll (even though I shouldn't need them I don't think)

Once I added qoffscreen.dll I now get the additional message: Available platform plugins are: offscreen

If I run through Dependency Walker I get this error listed:

GetProcAddress(0x76CA0000 [KERNEL32.DLL], "GetCurrentPackageId") called from "MSVCR110.DLL" at address 0x6AC6FDFA and returned NULL. Error: The specified procedure could not be found (127). 

and then further down get the:

GetProcAddress(0x745A0000 [UXTHEME.DLL], "BufferedPaintUnInit") called from "COMCTL32.DLL" at address 0x745FFBF8 and returned 0x745AE18C. This application failed to start because it could not find or load the Qt platform plugin "windows".  Available platform plugins are: offscreen.  Reinstalling the application may fix this problem. 

Any ideas how to fix this dll issue?

Answer 1

The error is caused because the program can't find qwindows.dll

qwindows.dll has to be in a folder named platforms so that the path from your executable to the dll is platforms/qwindows.dll

Whereas this wasn't enough in my case. I had also to add following line at the beginning of my main()

QCoreApplication::addLibraryPath("./"); 

Then everything worked.