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Thread: Qt4 plugin path problem

  1. #1

    Default Qt4 plugin path problem

    I have a problem with QT4 plugin path which is hard-coded into QtCore4.dll directly. I have tried to use addLibraryPath or setLibraryPaths but both didn't work. The only way I can make it work is change the hard-coded path in QtCore4.dll using a hex editor but I don't think it is a good way. Does anyone have a good solution on it?

    Thanks

  2. #2
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    Default Re: Qt4 plugin path problem

    When do you invoke that method? QCoreApplication loads plugins when you create its instance. Adding a path after the plugins were loaded won't help.

    Also Qt docs say:
    You can also use a qt.conf file to override the hard-coded paths that are compiled into the Qt library. For more information, see the Using qt.conf documentation. Yet another possibility is to set the QT_PLUGIN_PATH environment variable before running the application. If set, Qt will look for plugins in the paths (separated by the system path separator) specified in the variable.

  3. #3

    Default Re: Qt4 plugin path problem

    I invoked the function right after QApplication a(argc, argv);
    Here is my code:

    QApplication a(argc, argv);
    QString path;
    path = QCoreApplication::applicationDirPath();
    QCoreApplication::addLibraryPath(path);

    I tried to call that function before initiating the qApplication:
    path = QCoreApplication::applicationDirPath();
    QCoreApplication::addLibraryPath(path);

    QApplication a(argc, argv);

    But I got the following error message:
    QCoreApplication::applicationDirPath: Please instantiate the QApplication object first

    That's all I got so far.

  4. #4
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    Default Re: Qt4 plugin path problem

    You don't have to add applicationDirPath() to library paths --- it's already there. Just make sure that plugins are in proper subdirectories.

    Which plugins do you need?

  5. #5

    Default Re: Qt4 plugin path problem

    I need gif and jpeg plugins which are stored in \QTDIR\plugins\imageformat directory. Actually these plugins are called by QtCore4.dll, instead of my program. I want to put all these DLLs to the program folder when I deploy the application. Now, I have to change the hard-corded plugpath in QtCore4.dll and install the plugin dll into a fixed folder such as c:\qt4\plugins.

    My goal is to put plugin DLLs to the folder that stores my exe file. That's why I add applicatioon path to the LibraryPath.

    Thanks for your help:-)

    David

  6. #6
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    Default Re: Qt4 plugin path problem

    Quote Originally Posted by david.corinex View Post
    My goal is to put plugin DLLs to the folder that stores my exe file.
    If xxx is one of the "library" paths, Qt will look for image plugins in xxx/imageformats subdirectory.

    What does QCoreApplication::libraryPaths() return on your system?

  7. #7

    Default Re: Qt4 plugin path problem

    Oh my....

    I forgot QtCore4.dll will search plugins in /newpathdir/imageformats directory. I will try this today:-)

    Thanks for your great hints!
    David

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