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Problem with TextEdit

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  • K Offline
    K Offline
    kay2e4
    wrote on last edited by
    #1

    I have created a software to receive packets from another pc, the software is to read the raw data of the packet, it works, it can receive packets. However, some of the text are not shown, as in, when then text is shown, a while later the text will disappear and to reveal the text, I have to highlight that area, I am trying to append the raw data received as string, is there any other widgets that are suitable for appending or shown huge number of string other than TextEdit, because I wish to see all the data instead of the white spaces and I have to highlight the white spaces to see the oncoming packets.

    P.S: I am using the append function to append all the raw data on to the TextEdit, is it the problem lies with me using the wrong function? So should I use append?

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    • C Offline
      C Offline
      CreMindES
      wrote on last edited by
      #2

      Could you post some code snippet to highlight ( :D ) your problem's roots?

      Maybe you coud use QTextView if you do not want to edit your data, and for this aplication QPlainTextEdit is also good, but the latter is almost the same as QTextEdit, it's just for plain text.

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      • A Offline
        A Offline
        andre
        wrote on last edited by
        #3

        Just from the description, it sounds like a bussy loop receiving the updates, and then not letting the eventloop do it's job of making sure the widget gets repainted... However, I might be completely off, not having seen a single line of relevant code.

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        • K Offline
          K Offline
          kay2e4
          wrote on last edited by
          #4

          Ok I will post the codes here but it is a bit wordy, and i have tried using plain text edit, it didnt even display the packets, unlike the textedit, but due to some lines of data suddenly disappear or didnt even show, I have to show them by selecting the empty areas

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          • K Offline
            K Offline
            kay2e4
            wrote on last edited by
            #5

            @while (1) {
            // Call recvfrom() to get it then display the received data...
            ByteReceived = recvfrom(ReceivingSocket, ReceiveBuf, BufLength,
            0, (SOCKADDR *)&SenderAddr, &SenderAddrSize);

            if (ByteReceived > 0)
            m_pReceiver->PrintInfo("\n\nServer: Total Bytes received: "
            + QString(ByteReceived)
            + "\nServer: The data is: "
            + QString(ReceiveBuf));
            else if (ByteReceived <= 0)
            m_pReceiver->PrintInfo("Server: Connection closed with error code: "
            + WSAGetLastError());
            else
            m_pReceiver->PrintInfo("Server: recvfrom() failed with error code: "
            + WSAGetLastError());
            @

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            • A Offline
              A Offline
              andre
              wrote on last edited by
              #6

              [quote author="kay2e4" date="1340719017"]
              @
              while (1)

              {
              // Call recvfrom() to get it then display the received data...
              ByteReceived = recvfrom(ReceivingSocket, ReceiveBuf, BufLength,
              0, (SOCKADDR *)&SenderAddr, &SenderAddrSize);

              if (ByteReceived > 0)
              m_pReceiver->PrintInfo("\n\nServer: Total Bytes received: "
              + QString(ByteReceived)
              + "\nServer: The data is: "
              + QString(ReceiveBuf));
              else if (ByteReceived <= 0)
              m_pReceiver->PrintInfo("Server: Connection closed with error code: "
              + WSAGetLastError());
              else
              m_pReceiver->PrintInfo("Server: recvfrom() failed with error code: "
              + WSAGetLastError());
              @
              [/quote]

              edit: Please use @ tags around code sections; Andre

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              • K Offline
                K Offline
                kay2e4
                wrote on last edited by
                #7

                done thanks for the advice, this is just a sample of the codes, so once i receive a packet from the sender it will display the raw data as string. I will try to post a picture of the software when running tomorrow in my school pc

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                • A Offline
                  A Offline
                  andre
                  wrote on last edited by
                  #8

                  It is exactly what I thought: you're not letting the event loop do it's work. Don't use a
                  @
                  while (1) { }
                  @
                  construct. Network communications in Qt are supposed to asynchronous.

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                  • K Offline
                    K Offline
                    kay2e4
                    wrote on last edited by
                    #9

                    i think i show u the entire set of codes just in case....

                    @int ReceiverThread::StartReceiver()
                    {
                    WSADATA wsaData;
                    SOCKET ReceivingSocket;
                    SOCKADDR_IN ReceiverAddr, SenderAddr;
                    int SenderAddrSize = sizeof(SenderAddr), Port = 5150, BufLength = 6000,
                    ByteReceived = 5, SelectTiming, ErrorCode;
                    char ReceiveBuf[6000];

                    // Initialize Winsock version 2.2
                    if( WSAStartup(MAKEWORD(2,2), &wsaData) != 0)
                    {
                        m_pReceiver->PrintInfo("Server: WSAStartup failed with error %ld\n"
                                               + WSAGetLastError());
                        return -1;
                    }
                    else
                        m_pReceiver->PrintInfo("Server: The Winsock DLL status is "
                                               + QString(wsaData.szSystemStatus));
                    
                    // Create a new socket to receive datagrams on.
                    ReceivingSocket = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
                    
                    if (ReceivingSocket == INVALID_SOCKET)
                    {
                        m_pReceiver->PrintInfo("Server: Error at socket(): " + WSAGetLastError());
                        WSACleanup();
                        // Exit with error
                        return -1;
                    }
                    else
                        m_pReceiver->PrintInfo("Server: socket() is OK!");
                    
                    // Set up a SOCKADDR_IN structure that will tell bind that we want to
                    // receive datagrams from all interfaces using port 5150.
                    
                    // The IPv4 family
                    ReceiverAddr.sin_family = AF_INET;
                    // Port no. 5150
                    ReceiverAddr.sin_port = htons(Port);
                    // From all interface (0.0.0.0)
                    ReceiverAddr.sin_addr.s_addr = htonl(INADDR_ANY);
                    
                    // Associate the address information with the socket using bind.  At this
                    // point you can receive datagrams on your bound socket.
                    if (bind(ReceivingSocket, (SOCKADDR *)&ReceiverAddr, sizeof(ReceiverAddr))
                        == SOCKET_ERROR)
                    {
                        m_pReceiver->PrintInfo("Server: bind() failed! Error: " + WSAGetLastError());
                        closesocket(ReceivingSocket);
                        WSACleanup();
                        // and exit with error
                        return -1;
                    }
                    else
                        m_pReceiver->PrintInfo("Server: bind() is OK!");
                    
                    // Some info on the receiver side...
                    getsockname(ReceivingSocket, (SOCKADDR *)&ReceiverAddr, (int *)sizeof(ReceiverAddr));
                    
                    m_pReceiver->PrintInfo("Server: Receiving IP(s) used: "
                                           + QString(inet_ntoa(ReceiverAddr.sin_addr))
                                           + "\nServer: Receiving port used: "
                                           + QString(htons(ReceiverAddr.sin_port))
                                           + "\nServer: I\'m ready to receive a datagram...");
                    
                    SelectTiming = RecvFromTimeoutUDP(ReceivingSocket, RCV_TIMEOUT, 0);
                    
                    switch (SelectTiming)
                    {
                    case 0:
                        // Timed out, do whatever you want to handle this situation
                        m_pReceiver->PrintInfo("Server: Timeout while waiting for client!...");
                        break;
                    case -1:
                        // Error occurred, maybe we should display an error message?  Need more
                        // tweaking here and the recvfromTimeOutUDP()...
                        m_pReceiver->PrintInfo("Server: Some error encountered with code number: "
                                               + WSAGetLastError());
                        break;
                    default:
                        while (1) {
                            // Call recvfrom() to get it then display the received data...
                            ByteReceived = recvfrom(ReceivingSocket, ReceiveBuf, BufLength,
                                                    0, (SOCKADDR *)&SenderAddr, &SenderAddrSize);
                    

                    if (ByteReceived > 0)
                    m_pReceiver->PrintInfo("\n\nServer: Total Bytes received: "
                    + QString(ByteReceived)
                    + "\nServer: The data is: "
                    + QString(ReceiveBuf));
                    else if (ByteReceived <= 0)
                    m_pReceiver->PrintInfo("Server: Connection closed with error code: "
                    + WSAGetLastError());
                    else
                    m_pReceiver->PrintInfo("Server: recvfrom() failed with error code: "
                    + WSAGetLastError());

                            // Some info on the sender side
                            getpeername(ReceivingSocket, (SOCKADDR *)&SenderAddr, &SenderAddrSize);
                            m_pReceiver->PrintInfo("Server: Sending IP used: "
                                                   + QString(inet_ntoa(SenderAddr.sin_addr))
                                                   + "Server: Sending port used: "
                                                   + QString(htons(SenderAddr.sin_port)));
                        }
                    }
                    
                    // When your application is finished receiving datagrams close the socket.
                    m_pReceiver->PrintInfo("Server: Finished receiving. Closing the listening socket...");
                    if (closesocket(ReceivingSocket) != 0)
                        m_pReceiver->PrintInfo("Server: closesocket() failed! Error code: "
                                               + WSAGetLastError());
                    else
                        m_pReceiver->PrintInfo("Server: closesocket() is OK...");
                    
                    // When your application is finished call WSACleanup.
                    m_pReceiver->PrintInfo("Server: Cleaning up...");
                    if(WSACleanup() != 0)
                        m_pReceiver->PrintInfo("Server: WSACleanup() failed! Error code: "
                                               + WSAGetLastError());
                    else
                        m_pReceiver->PrintInfo("Server: WSACleanup() is OK");
                    
                    // system&#40;"PAUSE"&#41;;
                    return 0;
                    

                    }@

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                    • K Offline
                      K Offline
                      kay2e4
                      wrote on last edited by
                      #10

                      The program is running on TextEdit but due to the disappearance of the text, I post this tread to ask whether is it a bug, and can it be solved, for now to solve it, I have to select empty area then the text will show... Is there a solution? The problem lies with the TextEdit

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                      • A Offline
                        A Offline
                        andre
                        wrote on last edited by
                        #11

                        Analysis stays exactly the same. Your while(1) loop is the main issue.

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                        • K Offline
                          K Offline
                          kay2e4
                          wrote on last edited by
                          #12

                          I am a novice in programming, so what do you suggest I use?

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                          • K Offline
                            K Offline
                            kay2e4
                            wrote on last edited by
                            #13

                            So I can assume once I solve the while(1) loop the TextEdit should have no problems right?

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                            • A Offline
                              A Offline
                              andre
                              wrote on last edited by
                              #14

                              Moderators note: please edit previous comments instead of posting a new reply seconds after your last one.

                              On topic: yes, getting rid of the bussy waiting loop will solve the issue, but doing that will require a re-design of your application.

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                              • K Offline
                                K Offline
                                kay2e4
                                wrote on last edited by
                                #15

                                so i just stay as it is?

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                                • A Offline
                                  A Offline
                                  andre
                                  wrote on last edited by
                                  #16

                                  No. You do the needed re-design. I was just trying to warn you that it might be trickyer than it looks initially to get rid of the loop. Just because something is difficult or a lot of work, does not mean it shouldn't be done or isn't worth doing.

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                                  • K Offline
                                    K Offline
                                    kay2e4
                                    wrote on last edited by
                                    #17

                                    So I just redesign the loop change it to another function, then it will work? Is that what you mean?

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                                    • A Offline
                                      A Offline
                                      andre
                                      wrote on last edited by
                                      #18

                                      You need to come up with an asyncronous design. A design that allows to return to the event loop after each time you add output to your text edit. If you just move the loop to another function, nothing has changed.

                                      Basically, instead of polling continuiously if there is new data to display, you need to switch to a design where either only poll at a specific interval, or much better, don't poll at all but react to a signal, event or interupt or something like that as the data actually comes in.

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