General and Desktop

• 

  How to create the plugin of MYSQL for Qt
  • BlackStar

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  @flydragon

  Do not duplicate posting because you do not get an answer immendiately.

  [edit:koahnig see https://forum.qt.io/topic/82629/why-qsqlquery-exec-exit-failed ]

• 

  Reporting inappropriate content on the forums
  spam • • Eddy

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  Thank you for the report. I have banned the user, which got rid of the spam posting. Not a loss, as this user did not post any other content on the site. Just deleting this one posting was not possible.

  Thanks for reporting this.

• 

  Unsolved Bug with setCurrentText on QComboBox
  • Kolya

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  @J-Hilk My bad - misinterpreted the documentation :-) Thank you for pointing out!

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  Unsolved Enabling exceptions to Qt project in Visual Studio 2017
  • TheEnigmist

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  No one has replied

• 

  Unsolved Serialport Timeout Error
  • QTlearner90

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  You should rethink your code globally.
  you can't use QThread::sleep(0.5) out of a QThread.
  Probably QThread::sleep(0.5) stops the application and the serial buffers.
  Please use QTimer if you have to send / receive continuosly.

• 

  Unsolved Implement low pass filter.
  • Siddhartha

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  @Siddhartha
  Hi
  well it could be a global function, but i think its better to make it a function of
  MainWindow just like the other functions.
  However, the simplp is a c function and uses a c array for the x,y but in plotter
  the data is in
  MainWindow::onNewDataArrived(QStringList newData)
  which is a Stringlist so you cant just copy the code and have it working.

  So first step is to read the text in link and understand how it works then change the code to use
  the newData list instead as the c code expects other type of list and must be rewritten slightly.

• 

  Unsolved noobie - using WinPCap
  • cmwDev

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  I have been making some progress. My loop code is:

  while((res = pcap_next_ex(fp, &header, &pkt_data)) >= 0) { QCoreApplication::processEvents(); if(res == 0) { // timeout elapsed continue; } // print packet timestamp and length sprintf(capBuff,"%ld:%ld (%ld)",header->ts.tv_sec, header->ts.tv_usec, header->len); sbuf = QString::fromLocal8Bit(capBuff); qDebug() << "CapString " << capBuff; ui->capText->appendPlainText(sbuf); sbuf = ""; for(i=1; (i < header->caplen + 1); i++) { sprintf(hexBuff,"%.2x ", pkt_data[i-1]); sbuf.append(QString::fromLocal8Bit(hexBuff)); if ((i % LINE_LEN) == 0){ qDebug() << sbuf; ui->capText->appendPlainText(sbuf); sbuf = ""; } } qDebug() << sbuf; ui->capText->appendPlainText(sbuf); qDebug() << ""; }

  Adding in the event processing lets the text box show the right data, it matches 100% to what the VS example processes. I still have a lot of tweaking to do, work on decoding the actual packet into english stuff.

  With that said, there is still the issue of running in debug mode and the 'd' value crashing the program. The new issue is most strange though. With the program running, I hit the 'x' close application at the top of the form, and as expected the form window terminates. Yet the program still runs, I still see information being displayed in the Application Output window. I had to click on the 'stop program' button in that window to actually get it to terminate.

  Why would it keep running after the main form closes?

• 

  Unsolved Can't configure properly my layouts
  • PP_RhuM

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  I Changed a little thing: I added all my controls (in the bottom of the CurveEditorWidget) in a simple widget container (see in the inspector) :
  

  In the structure, here are size policy (H / V):

  CurveEditorWidget = MinimumExpanding / Prefered curve_scrollArea = Expanding / Expanding optionsContainer_widget = MinimumExpanding / Prefered currentPointFunction_lineEdit = MinimumExpanding / Fixed All other widgets under optionsContainer_widget = Fixed / Fixed

  For the OperatorPanel widget:

  OperatorPanel = MinimumExpanding / Prefered pitchDials_widget = Maximum / Fixed All other widgets under pitchDials_widget = Fixed / Fixed

  I change the width of the instance of the OperatorPanel added dynamically to the main window. It's not placed in a layout, it's placed in the main window itself and positionned in an absolute place.

  Should i add another container to embed the operator panel widget like this ?

  QWidget *container = new QWidget(this); QHBoxLayout *container_hLayout = new QHBoxLayout(container); container_hLayout->addWidget(operatorPanel); container->setFixedWidth(this->width() - 5);

  It doesn't make really sense because the OperatorPanel widget should be sizable with size I want..

• 

  Unsolved Saving/Restoring OAuth2 tokens
  • kshots

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  Did you get this to work?

  I also have the need to store the token (to avoid entering credentials each time the application starts) but haven't found an official way to do it.

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  Unsolved when i write text on QLineEdit that text shows on QLabel
  • Dimple

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  @VRonin
  There's some sort of "history" mechanism going on here. The user types something somewhere, it is to be added to this list as the first item. User then types something again, this gets added as the next item in the list.... :)

  So to the OP, @Dimple: you need to write code so that after each text entered in the line edit it should insert/append one additional row, setting that row's text from the line edit.

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  Unsolved TCP connection for file transfer
  • Chandras002

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  @robcont_
  Not sure what you mean. @VRonin's code looks right to me. Transactions don't care (or know) whether QImages or anything else is being sent.

  I looked at the other question. I note you were using out.device()->seek(0);. I don't suppose that has consequences for the transactions? I didn't understand why you are doing that, why do you have to go back and put a size in instead of putting it in in the first place before the data?

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  Solved QUdpSocket : simple communication between 2 Qt applications
  • LeLev

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  OK. Client & Server is only terminology.

  Server is the one which is waiting for connection. Client is the one which is initiating the connection.

  Once connection is established client/server terminology w.r.t data transfer is blurred as both will start transferring the data.

• 

  Unsolved QImage streaming over TCP
  • robcont_

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  @robcont_ said in QImage streaming over TCP:

  As I said on the first post, I need these frames to rebuild a video-streaming. Tnx in advance.

  the QImage serialized over QDataStream is done by converting the image to a PNG data.
  Of course this approach isn't very well suited for streaming "video".

  It depends what your goals are . Is it ok to receive a "stuttering" video (due to your approach by transferring each frame)?
  It may be ok for a small resolution though.

  Normally classic video streams are optimized for their purpose of course.
  Like proper compression, drops of frames which are too far in the past to display, etc.

  But also this involves more research on this topic (video streaming).

• 

  Solved QTimer will not connect
  • BKBK

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  @jsulm said in QTimer will not connect:

  @BKBK said in QTimer will not connect:

  Do you have Q_OBJECT macros right at the beginning of C_GL_Strip_Chart body?

  Rookie and all, still, I am embarrassed at not thinking of that. Yes, that was my problem.
  And yes, we really do need to upgrade. But,..., the best reasons in the world do not help.
  Thank you
  Edit
  Two lines from the OP

  unsigned short return_value = 999; // gets changed to 0. Different type required here? return_value = connect( m_timer, SIGNAL( timeout()), this, SLOT( interval_timer() ) );

  I saw that return value somewhere but cannot find any documentation about it.
  Is there anything to discover what the return values mean and other functions that may have return values?

• 

  Solved QMenuBar: menu is hidden when moving window to another monitor
  • zulu

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  Sorry for a long break.
  After holidays i have returned to development.
  I have added new QTwidget line and everything is ok now.
  Thanks a lot

• 

  Solved QT Creator Serial Port Plotter
  • priscilla v

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  @priscilla-v
  Hi welcome back
  funny enough, its being discussed here
  https://forum.qt.io/topic/98570/implement-low-pass-filter
  for same program :)

• 

  Unsolved Qt Embedded: displaying on two screens using QGraphicsView and QGraphicsWidget
  • dmudric

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  I am not using QWS Client-Server architecture. Only MainWindow, QGraphicsScene and QGraphicsView. I want to avoid any major redesign to support two screens. Qt5 is not an option. Have to stay with 4.8.

  http://doc.qt.io/archives/qt-4.8/qt-embedded-running.html ("Using the Multi screen driver, on the other hand, applications can easiliy be moved between the various screens."). Where are the examples of this easy implementation?

  Is there somebody in QT who knows how to make it working with the pseudo code above?

  Thanks,
  Dusan.

• 

  Unsolved LINK 1104 Error
  • lee64456546

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  @lee64456546 said in LINK 1104 Error:

  libxl-3.8.2.0/lib/libxl.lib

  You're using a relative path. You should rather use

  LIBS += $$PWD/libxl-3.8.2.0/lib/libxl.lib

  Adjust the path above if needed to your directory structure.

• 

  Solved Qt MQTT and while loop
  • Guigiidre

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  Great, it works, Qtimer was the solution.
  Thank you!

• 

  Unsolved Loader vs ?
  • MScottM

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  @MScottM said in Loader vs ?:

  I originally tried to use Q_PROPERTY(Variable variable READ variable WRITE setVariable NOTIFY variableChanged), but could never quite get it working and got frustrated and moved on. Since, though I have wondered it it would have the behavior I'm looking for - that you describe.

  It should provide you with what you are looking for. When you tried to get it working what was not working about it? I embed my onChanged signals into the setter methods and check if the variable has actually changed.

  I have a UIBridge class that passively grabs signals and updates its copy of the variables locally. My QML is connected to the bridge and my QML implementation is as simple as:

  Text { id: opName text: UIBridge.loading ? "" : UIBridge.user.operatorName }

  If you notice I even have boolean variables I am referencing for conditional stuff as well. By simply setting my c++ boolean "loading" to true I clear what is being displayed in the text component. QML knows the boolean change and handles it accordingly.

  I will add doing Q_PROPERTY() with custom classes that inherit QObject does not seem to work very well... Due to the copy constructor being disabled. I haven't figured out the best way to deal with this but my work around was to use pointers.

  Q_PROPERTY(Operator* user READ getUser NOTIFY userChanged) Q_PROPERTY(Shoporder* shoporder READ getShoporder NOTIFY shoporderChanged) Q_PROPERTY(Part* part READ getPart NOTIFY partChanged) Q_PROPERTY(EquipmentSettings* equipmentSettings READ getEquipmentSettings NOTIFY equipmentSettingsChanged) Q_PROPERTY(Limits* limits READ getLimits NOTIFY limitsChanged)

  Where my getters return the pointer (obviously). Other more base data types work just fine with the Q_PROPERTY macro.

  To connect my class instance to QML have these lines in cpp:

  QQmlApplicationEngine engine; /* add the bridge to the QML engine */ UIBridge uiBridge; engine.rootContext()->setContextProperty("UIBridge",&uiBridge); //in QML my object name is "UIBridge" /* start the engine */ engine.load(QUrl(QStringLiteral("qrc:/main.qml"))); if (engine.rootObjects().isEmpty()) return -1;
• 

  Unsolved QNetworkReply and setReadBufferSize problem
  • Hergest

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  This is a pseudocode of the function:

  ... netReply = m_pNetManager->post(req, qb_json); netReply->setReadBufferSize (64*1024); ... /* Reading some head data from netReply*/ ... size_blob = we get the size of the Blob to download from server ... /* Blob Reading from netReply // Loop while (...some conditions...){ ... Debug () << "bytesAvailable=" << netReply->bytesAvailable() << "bufferSize=" << netReply->readBufferSize(); qint64 bytes_read = 0; qint64 bytes_to_read = 1024*64; // chunk to download if ((bytes_read + bytes_to_read) > size_blob) bytes_to_read= size_blob - bytes_read ; qint64 parcial = netReply->read (reinterpret_cast<char*>(buffer_temporal), bytes_to_read); if (parcial > 0){ tmp_file.write (reinterpret_cast<const char*>(buffer_temporal), parcial); bytes_read += parcial; if (bytes_read >= size_blob){ // END READING status = 2; } } ... }

  The real code reads the data sent by the server, first a header and then a blob (in 64KB chuncks), then another header and its blob, and so on.
  In my tests, the value of "bytesAvailable" increases and surpasses "bufferSize", until the memory collapses.
  When I'm debugging it, in a breakpoint, I check that the server stops sending data. As soon as I resume it, "bytesAvailable" continues to increase, and the server continues sending data (data from other blobs).
  I have tried many combinations of chunks, ReadBufferSize values, ...

  This leads me to think...

  The server sends data whenever the client requests it. In the breakpoint it stopped doing it. Client keeps asking for data even though "readBuffer" fills up.
• 

  Solved Fill all space in QLayout
  • ivanicy

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  @J.Hilk
  Wow! thank you very much!! That works fine!

• 

  Unsolved How to use QStackedwidget without using designer form ?Also should be capable of navigating between pages when button is clicked.
  • Mahendra HD

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  @Mahendra-HD said in How to use QStackedwidget without using designer form ?Also should be capable of navigating between pages when button is clicked.:

  So please help me to navigate between pages using QStackedWidget when button is clicked

  See http://doc.qt.io/qt-5/qstackedwidget.html#currentIndex-prop

• 

  Unsolved Compile qt-5.4.1 with vs2017 got error.
  • mic19

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  @mic19 Can you upgrade to a newer Qt version?

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  Solved GStreamer : Pipeline to connect VNC server and Display/Record the remote GUI
  • LeLev

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  Maybe another encoder could work better.

  No, QVNCClient is not from me, I just found it :)

• 

  Solved QFlags is only usable on enumeration types
  • medihe

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  That is right.

  Thank you very much for your help.

• 

  Unsolved resize QImage in TableView
  • Pada_

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  There is QImage in the 0,0 Index of QTableView.

  How is it saved in the model?

• 

  Unsolved Some error occuring on destructor
  • Ovidiu_GCO

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  @Ovidiu_GCO
  ah alright, you made the ui form independet from your class and than added it afterwards, alright.

  PS. thanks, fixed the obvious typo :P

• 

  Solved How to automatically add some actions to context menus
  • JonB

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  Well here is the outline of what I have implemented, bearing in mind my desire to make as little code changes as possible and to provide the basic export facility quite "transparently" & automatically to all existing JTableViews which do not have their own context menus to add in.

  Step 1 is just to make JTableView's constructor go setContextMenuPolicy(Qt.CustomContextMenu) and set its own slot on customContextMenuRequested to its own openContextMenu() method which displays its export custom menu. At this point all existing JTableViews have the export menu without them even knowing about it/changing any of their code. That deals with 50% of client cases, with 0 lines of code changes.

  Step 2 is to handle those callers which already have their own customContextMenuRequested slot registered (after the JTableView has been created and registered its own) with their own menu. The problem is that will lead to 2 separate menus being shown, one after the other, and the caller-specific one won't be called till after the JTableView's one has executed, so it will be too late to do anything about that at that point.

  So I provide a JTableView.replaceCustomContextMenuRequested() which accepts the caller's own slot as a parameter: it disconnect()s its own slot first and then registers the caller's slot in its place. The caller's slot code builds its own menu as before, but now instead of displaying it directly it passes it to JTableView's openContextMenu() which merges that with its own export menu and then displays it for the caller. This deals with the remaining 50% of client cases, at just 2 lines of code changes per client.

  Ugly? Possibly. But achieves desired with minimal changes, and it's not that bad is it?

• 

  Solved error LNK2001: unresolved external symbol "public: static struct QMetaObject .. from lib template
  • OPit

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  Well, I rebuilt QtAV with a new installation of Qt, and it works ....
  So, even if I didn't understand the mistake, thanks a lot for your help !

• 

  Unsolved Enter admin rights once, use it in multiple process calls to terminal [Linux]
  • fleppe

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  @fleppe
  And there was I thinking pkexec was something to do with running some pkzip command.....

  This "polkit" stuff is all very good, and if that's what you want to use fine. But it's going to require a bit of setting up to use. I do not know how much configuring you want to do, or how "secure" you need to be for your purposes.

  I will just say that in terms of "simplicity", if that's really what you want, my two thoughts would be:

  Use sudo and rely on what I quoted from the man page to ensure the user only gets prompted for password once every 15 minutes, if that works for you.

  Use setuid. It sounds like all your commands are apt updates? I would not make your Qt program itself setuid (unless you really know what you are doing). Rather, a tiny executable wrapper program supplied with your Qt app to just do apt update with setuid would suffice (installed with just chown root & chmod u+s). I would suggest this might be the simplest solution if you want to avoid any password prompting at all, as per your original question. Have you at least considered/do you know about setuid, even if you have good reason to reject it?

• 

  Unsolved CGAL - Insert edge in a face
  • nmya

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  @SGaist thank you for help :)

• 

  Unsolved what is the suggestions for Sending frames to multiple threads and keep their order to properly show on the screen
  • RahibeMeryem

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  @RahibeMeryem You could have an increasing id for each frame and use this id to know the order.

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  Unsolved My Qt application in Centos always crashed ,but I do not changed any code ? just del a blank
  • Shae

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  @Shae The content of you pro file will not help to identify the problem.
  Please run through debugger and post stack trace when the app is crashing.
  Else there is no way to tell you why it is crashing (you did not even post the relevant code).

• 

  Solved what is the correct way to implement a Database class in a application
  sqlite database desktop qt5.5 • • realhamidrezakp

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  What do you mean by modify the model ?

  i mean updating model , like a search window that needs to update model every time user change input.

  You can see how to handle QtSQL models and views in the QtSQL modules examples.

  i saw it, and figure out some of examples. but i need to read more about MVC in qt.
  thanks you.

• 

  Unsolved How to convert QVariant to HTML
  • Mikeeeeee

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  I have .docx file.
  I get simple text from .docx:

  QString ResumeFileName (""); ResumeFileName = QFileDialog::getOpenFileName(0, "Text ", "", "*.doc *.docx *.rtf"); ResumeFileName.replace(QRegExp("[/]"), "\\"); qDebug()<<ResumeFileName; if (ResumeFileName != "") { QAxObject wordApplication("Word.Application"); QAxObject *documents = wordApplication.querySubObject("Documents"); QAxObject *document = documents->querySubObject("Open(const QString&, bool)", ResumeFileName, true); QAxObject *words = document->querySubObject("Words"); QString TextResume; QString HTMLResume; int countWord = words->dynamicCall("Count()").toInt(); for (int a = 1; a <= countWord; a++){ TextResume.append(words->querySubObject("Item(int)", a)->dynamicCall("Text()").toString()); HTMLResume.append(words->querySubObject("Item(int)", a)->dynamicCall("Text()").SomethingFfunction); } document->dynamicCall("Close (boolean)", false); TextResume.replace(QRegExp("[\r]"), "\r\n"); qDebug()<<TextResume;

  But I also need text with formatting and pictures

• 

  Unsolved UI Resposiveness + Multithreaded TCP server-client (UI lags, slow, less responsiveness when 2 client connected)
  reponsiveness lagging threading • • VikramSamy

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  @J.Hilk said in UI Resposiveness + Multithreaded TCP server-client (UI lags, slow, less responsiveness when 2 client connected):

  @VikramSamy

  taking what @jsulm said to heart, I would suggest the following.

  store all your (after processing) data in a struct and check if any data was actually updated with new values and only then try to emit signals to the ui-thread.

  For emitting the signal to the UI. I would suggest a QTimer and a QTime object. You save the time you last updated the UI, if the time is < than 16 ms (roughly 60hz rate) shedule an update for the next Frame via QTimer if more time passed, send the signal directly.

  You can pass structs in a signal (across threads), if you register it with the Meta-object System

  currently the architecture works similar by passing the processing data in a struct through a signal(across threads) but the signal is immediately emitted once the processing done, there no schedule to update as your suggestion. anyway currently the client is updating every 0.01s (100ms) and as per that the UI have sufficient time refresh itself without getting lag/slow. so far it is working fine.

  Anyway as the data received is to update UI which is 'bar-graph like indicators" which looks like a real time HI-FI graphic equalizer which rises up or down according to signal strength, as per that i just want to continue updating it although there is no status change received, as u suggest i try to update only when status change, but it cause the bar graph patterns getting stalled and not so nice,not going up & down nicely, so as per that i just continue updating no matter got changes or not ...anyway i got another idea as below:-

  as i told before there is 2 PLC updating the server with the same set of data's, one is for redundancy purpose..as both will run in their own separate thread when both is connected and the respective threads emits a signal after completing the data parsing,then the UI update slot is called to refresh the UI to latest status.

  The idea now is to use only 1 set of data from only 1 thread and not use the data returned from the other thread, because updating the UI constantly with same set of data's also another waste processor time and makes the UI lagging and slow.

  So how to block a thread, and only let 1 thread to continuously processing while blocking the other thread,to achieve something as below :- e.g

  thread A and thread B is created after both PLC1 and PLC2 is connected, but only the data returned from thread A is used to update the UI and thread B is blocked from running, thread B only can run if thread A is deleted when the PLC1@client is disconnected and VICE VERSA.

  in other words when both client connected, only thread A data will be used and Thread B must be ignored, if PLC2@client is disconnected then use thread A data from the connected PLC1@client, and when PLC1@client is disconnected then use thread B data....something like this..

  as im new to multi threading or thread based program and also QT, i just try to implement flag in the struct passed by the thread, which states if both client is connected and etc , and checking it before update the UI but it doesnt work...my questions is do we need to use something like mutex or any kind of locking mechanism or this can be achieve by simple flag based communication like in normal embedded c program without threads,

• 

  This topic is deleted!
  • Bharth

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  Solved UI Responsiveness and QListView updating during load of large data into model
  model-view responsive • • bepaald

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  Boiler plate code which you are trying to implement is already taken care by Qt using Signals/Slots across threads. It is better to use tried & tested inbuilt mechanism. It is good with code maintainability & readability as well. Suggest to use signals/slots.

• 

  Unsolved virtualkeyboard released by QT 5.12 didn't work
  • GreenM

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  No one has replied