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"Not responsing..." window when using lots of data

  • I develop a program which cipher and decipher any file (Project "CryptoFiler". After some experiments i figured out that there is a "not responsing..." at the window when I load a program with 5 MB or more. I was thinking about using QThread, but I'm not very confident with multithreading yet.

    I have to wait until the algorithm is done with (de)cipher progress, then I can continue with it. I fear that some users may try to quit the program by force when the program can't respond. Any suggestions?

    lg enforcer

    PS: As an improvement I thought about adding a progress bar. After the first test (2 KB) it took longer than without one. If you have a solution for that then very thank you.

  • Show the user a message - "Work in progress - don't close the application. It may take a few minutes." The simplest things are often the best :)

  • Have a look at QCoreApplication::processEvents() . It's much simpler than multithreading.

  • Because I think it won't be easy to break up the decryption into smaller blocks, I think using a thread is your best bet. Note that you could use one of high-level primitives. Instead of using a QThread directly, you could consider using QtConcurrent::run. That returns a [[doc:QFuture]], on which you can create a [[doc:QFutureWatcher]] to get a signal when the task is done.

  • Thanks for your suggestions. I will try all of them and choose the one I think is the best.

    When the application is ready after some tests I will create a Linux (and maybe a Mac OS) version of it. The algorithm uses binary mode for reading/writing.

    To Hostel:
    That sure is the simplest way ^^

    To john_god:
    I never thought about using a different process, though I used it in a Raytracing algorithm for computer graphics to safe time (1920x1080 sure takes its time).

    To Andre:
    I can't break them up. If I do, the application might write data blocks in wrong order.
    I read a block from std::ifstream, cipher it and write it into std::ofstream. That way I don't have to allocate anything into the memory (25 MB was highest according to Microsoft Task Manager).

  • I still need to try the QThread way. I found two different ways to create threads:

    Create a QObject which has at least one signal to show that the thread is finished and connect it to a thread (Zander's link). Then use QThread::start();

    Create a class which is derived from QThread and write the function into protected "run" method. Then use QThread::start();

    Two different parties and all of them says that the other one it the wrong way. What shall I believe now.

    To Hostel:
    I tried to create a QMessageBox with a message that it might take longer. A message box appeared, but except for the titel there only was a blank window without a text (see code below). As another solution I could use a QLabel which says "Please wait..." during the process and disappears afterwards.
    @QMessageBox msg(QMessageBox::NoIcon, "Cipher process", "Process may take some time. Please wait...");
    msg.setInformativeText("Process may take some time. Please wait...");
    bool ok = crypto_->cipher(...);

    To john_god:
    I somehow can't manage to create another process where the cryptic process occures. it's different from <windows.h> library. I might get problems when i try to export this to Linux/Mac OS.

  • The suggestion to use signals is from the creator of the thread classes himself;

    I agree with him, you practically never want to subclass QThread.

  • [quote author="Thomas Zander" date="1360153191"]The suggestion to use signals is from the creator of the thread classes himself;

    I agree with him, you practically never want to subclass QThread.[/quote]

    Ok, thanks for info. I have one last question:

    The project's/program's name is "CryptoFiler". 2 days ago I heard that there already is a software called "Acid Cryptofiler" developed by french military [1]. I don't know now if I can use the name or if there is a patent. Is there a website where I can find this out without payment?

    [1] "":

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