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.

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  Unsolved match font family return from QFont::toString()
  • user4592357

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  Hi,

  Please, show your code and the Qt version you are using. This expression works both with QRegularExpression (which you should be using) and the deprecated QRegExp.

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  Unsolved QProcess SIGSEGV (0.02 Bitcoin Bounty)
  • Bushstar

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  Hi,

  What kind of application is minerd ? Also Qt ?

  Do you get the same crash if you start another application like .e.g ls ?

• 

  Unsolved problem while making a qt program
  qlistwidget qt5.9.1 • • vasu_gupta

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  Hi,

  Can you show your .pro file ?

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  Unsolved Increase in memory when using QMetaObject::invokeMethod with qvarientlist
  • Tirupathi Korla

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  This is the function in cpp.

  void myClass:: callBack(QByteArray ary){ QVariantList reports; reports.append("test:"); temp_report * t = ((temp_report*)(ary.data())); QString str = t->value; str.append(" $"); reports.append(str); QMetaObject::invokeMethod(qmlRootObject, "callMoneyFunction", Q_ARG(QVariant, reports)); reports.clear(); ary.clear(); }

  Below is qml code

  function tempCallback(value){ var str = sourceModel.get(0).value; sourceModel.remove(0) sourceModel.insert(0,{"key": "Temp: " + value[0],"value":str }); }

  SourceModel is listmodel of tableview.

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  Unsolved Encoding issue with mysql and Arabic - Qt 5.8 on windows 7
  mysql qtableview qsqlquerymodel • • Script22

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  set data as ( utf8_general_ci ) not ( utf8_unicode_ci ) and test it

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  Unsolved is it possible streaming video via network?
  • liewjls

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  No one has replied

• 

  Unsolved Problem with checkbox ,spinbox and qcustomplot
  • Leopold

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  Hi SGaist,
  I see you live in switzerland so I write in german.
  Das Programm ist ein Testprogramm für austin mini Motorsteuerung ursprünglich von Colin Bourassa unter GPL geschrieben. Ich habe es um einige Anzeigen erweitert und möchte die Ausgabewerte auch in einem Plotfenster als Kurve ausgeben.Dazu zu jedem Wert eine checkbox.!Einschränkungen habe ich ja dadurch gemacht, das die Spinbox auf 0 stehen muß,ich könnte noch einen else Zweig hinzufügen falls keines der Kriterien erfüllt ist.Mit diesem Fehler bricht das Programm ab, wo muß ich suchen.:QCPGraph* QCustomPlot::graph(int) const index out of bounds: 3
  Gerne schicke ich auch den kompletten source code.Da meine c Kenntnise nur grundlegender Natur sind komme ich nicht weiter.
  Gruß
  Leopold

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  Solved android copy text file/folder to server
  • liewjls

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  This has been resolve which i'm using the example from https://stackoverflow.com/questions/23344370/qhttpmultipart-upload-multiple-files.

  thanks

• 

  Solved speed up QTableview with large data
  qtableview qtableviespeed • • oxycoder

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  Thanks everyone for answer.
  I am end up with write my own models, the load time reduce to 3s for 30k row and 150 col each.

• 

  Unsolved How to split Array
  array c++11 websocket string integers • • Geeva

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  @Geeva
  The easies way is to move your task into its own function that expects q QList<QString> as an argument:

  void myClass::myFunction(QList<QString> startvalue){ //do stuff eg: qDebug() << "Value Received from server :" << startvalue; QStringList first = startvalue.split("|"); int firstSize = first.size(); qDebug() << "size :" << firstSize; if(firstSize == 5){ first1 = first[2]; first2 = first[3]; }..........(continue) }

  then you call that function for each and every item in your QList<QList<QString>>

  QList<QList<QString> > myList for(QList<QString> ls : myList){ myFunction(ls); }
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  Solved How to partially draw a QGraphicsPixmapItem
  • Damien

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  @Asperamanca said in How to partially draw a QGraphicsPixmapItem:

  case I would not use the QGraphicsPixmapItem (not much code in it, anyway), but rather create a custom QGraphicsItem that simply paints only the portion of the p

  Thanks @Asperamanca. I went that route and it was very straight forward. Performance is acceptable too.

  imageitem.h

  #pragma once #include <QGraphicsItem> class ImageItem : public QGraphicsItem { public: ImageItem(QGraphicsItem* parent = Q_NULLPTR); ~ImageItem(); public: void setImage(const QImage& pixmap); QRect imageRect() const; QRectF boundingRect() const; void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget = Q_NULLPTR); void setSubRegion(const QRectF& rect); protected: QImage m_image; QRectF m_boundingRect; QRectF m_target; QRectF m_souce; };

  imageitem.cpp

  #include "imageitem.h" #include <QPainter> ImageItem::ImageItem(QGraphicsItem* parent /*= Q_NULLPTR*/) : QGraphicsItem(parent) { } ImageItem::~ImageItem() { } void ImageItem::setImage(const QImage & image) { m_image = image; m_boundingRect = m_image.rect(); } QRect ImageItem::imageRect() const { return m_image.rect(); } QRectF ImageItem::boundingRect() const { return m_boundingRect; } void ImageItem::paint(QPainter * painter, const QStyleOptionGraphicsItem * option, QWidget * widget) { Q_UNUSED(option); Q_UNUSED(widget); painter->drawImage(m_target, m_image, m_souce); } bool ImageItem::setSubRegion(const QRect & rect) { QRect imageRect = m_image.rect(); if (imageRect.contains(rect)) { m_souce = rect; m_target = QRect(0, 0, rect.width(), rect.height()); m_boundingRect = m_target; update(); return true; } else { return false; } }
• 

  Unsolved QNetworkAccessManager purges cookies if following redirect
  qtnetwork qnetworkaccessm redirect cookies • • Jiloc

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  @raven-worx I am not talking about multiple requestes. It's a problem with the single request.

  If i send a request like that:

  SsoNetworkManager::SsoNetworkManager(QObject *parent) : QNetworkAccessManager(parent) { connect(this, SIGNAL(authenticationRequired(QNetworkReply*, QAuthenticator*)), this, SLOT(onAuthenticationRequired(QNetworkReply*,QAuthenticator*))); connect(this, SIGNAL(finished(QNetworkReply*)), this, SLOT(onFinished(QNetworkReply*))); } void SsoNetworkManager::onAuthenticationRequired(QNetworkReply *reply, QAuthenticator *auth) { auth->setUser(QString("test")); auth->setPassword(QString("test")); } void SsoNetworkManager::onFinished(QNetworkReply *reply){ qDebug() << reply->attribute(QNetworkRequest::HttpStatusCodeAttribute).toInt(); } ... SsoNetworkManager nam; QNetworkRequest request("http://127.0.0.1:8000/admin/"); request.setAttribute(QNetworkRequest::FollowRedirectsAttribute, true); nam.get(request); ...

  The server works like that

  302 and redirects to /admin/login/ 401 asking for basic auth 302 , sets cookie sessionid and redirects to /admin/ reads sessionid and replies with 200

  If i follow this procedure with the browser or with python it works like a charm.
  If i try this with the code above the server does't receive any cookie, they are always empty, and the client enters in a redirect loop.

  I just tried to remove the QNetworkRequest::FollowRedirectsAttribute and manually handle the redirects. This way it stores the cookies, but I don't want to keep doing it manually.

  To me it seems a bug

• 

  Unsolved Have to put an icon on file extensions of a program on Windows explorer
  • tomy

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  I this time removed the code:

  QSettings reg("HKEY_LOCAL_MACHINE\\SOFTWARE\\Classes\\.sp\\DefaultIcon", QSettings::NativeFormat); reg.setValue("Default", "C:\\Users\\Tomy\\Desktop\\Spreadsheet.ico"); SHChangeNotify(SHCNE_ASSOCCHANGED, SHCNF_IDLIST, NULL, NULL);

  from both void MainWindow::readSettings() and void MainWindow::writeSettings() functions and added it to the MainWindow's constructor body, then re-did the rest and installed that new on my Windows.
  Again, no changes in result!!
  There might be a problem either in the code or the script file.

• 

  Unsolved QString encoding problem
  • sonulohani

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  @sonulohani said in QString encoding problem:

  how do i convert it into the character.

  what do you mean?
  A "character" is just data. It just matters if you interpret it as a (Unicode-)character.
  Thats why i asked how you exactly check for those "invalid" characters?

• 

  Unsolved how to put hex numbers into a Qbytearray?
  • Nimika

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  @mostefa if we go that far, QByteArray accepts an int value as constructor:

  QByteArray byteArray1(61455); //or QByteArray byteArray2(0xF00F);
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  Unsolved No QWebEngineCallback Qt5.6.3 Ubuntu16.04
  • PatrickK

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  @PatrickK Did you try

  #include <QWebEngineView>

  ?

• 

  Solved QtSerialPort blocking write in raspberry pi(raspbian pixel)
  • Vasily S

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  @aha_1980 Many thanks, everything turned out. The problem was in the kernel buffer.

  It works

  #include <termios.h> ... void SerialTransport485::write(const QByteArray & msg) { mGPIO.writeState(GPIO::IOEnable, GPIO::Set); mPort->write(msg); mPort->flush(); int serialHandle = mPort->handle(); tcdrain(serialHandle); mGPIO.writeState(GPIO::IOEnable, GPIO::Reset); }
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  Unsolved QScrollArea Image Loading
  • Thanasis

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  Solved Emit signal from static function issue
  • Cobra91151

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  I have fixed the issue:

  I set this to the function:

  WlanRegisterNotification(hClient, WLAN_NOTIFICATION_SOURCE_ALL, TRUE, notificationCallBack, this, NULL, &dwPrevNotif); void WINAPI WirelessConnect::notificationCallBack(PWLAN_NOTIFICATION_DATA wlanData, PVOID context) { //context = NULL; WirelessConnect *pThis = (WirelessConnect*) context; switch (wlanData->NotificationCode) { case wlan_notification_acm_connection_complete: pThis->apConnectionComplete(); qDebug() << "Connected!"; break; case wlan_notification_acm_connection_attempt_fail: pThis->apConnectionFailed(); qDebug() << "Failed!"; break; default: break; } }

  Then connect it as not static instance:

  connect(wirelessAPConnect, &WirelessConnect::apConnectionComplete, this, &Test::setAPConnection); connect(wirelessAPConnect, &WirelessConnect::apConnectionFailed, this, &Test::setAPConnectionFailed);

  So I don't need the static global instance anymore and it works now.

• 

  Solved How to generate Uuid based on system MAC address
  • rakeshthp

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  @rakeshthp said in How to generate Uuid based on system MAC address:

  I want to generate Uuid based on the system's MAC address using Qt. I could not find suitable example to do so. I am able to produce the mac address. Can someone guide me in order to implement this?

  find MAC

  QStringList m_list_mac; foreach(QNetworkInterface interface, QNetworkInterface::allInterfaces()) { // Return only the first non-loopback MAC Address if (!(interface.flags() & QNetworkInterface::IsLoopBack )&& (interface.flags() & QNetworkInterface::IsUp)) { m_list_mac.append(interface.hardwareAddress()); } }

  and used for crypt QCryptographicHash
  as recommended raven-worx

• 

  Unsolved How can I see and storage the data from device in QT?
  • segtteee

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  @segtteee Yes you can

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  Unsolved How can i store the values?
  • lordumuzca

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  @lordumuzca
  I didn't understand precisely what and where you want some values to store, but a general approach in such cases, as I think, is to sub-class the parent you need and add suitable fields.

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  Unsolved Multi threaded server with separate database connection for every users
  • red_spider

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  No one has replied

• 

  Solved Qt Creator doesn't see contents of included header file
  • michalos

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  Converting the header file to UTF-8 encoding did the job.

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  Unsolved How can i show data that device sent in QT?
  • segtteee

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  @J.Hilk
  thanks, it was not occured error after writing the code "connect(qApp,&QApplication::aboutToQuit,popUp,&QLineEdit::deleteLater);"

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  Solved Stylization
  • Tikani

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  @kshegunov
  I was an idiot :D It turned out that I totally forgot to clean and rebuild project from time to time and files specified in the resource file were not recompiled and embedded to the executable. But thanks anyway for clarifying.

• 

  Solved Cannot retrieve the SQL query string from QSqlQuery?
  qsqlquery • • JNBarchan

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  @jsulm said in Cannot retrieve the SQL query string from QSqlQuery?:

  @mostefa This is not the answer to the question as @JNBarchan want to have the query text not its result.
  From your example he wants to get "SELECT id,name,birthday FROM artist".

  @mostefa As @jsulm says, I am indeed not looking to execute the query, rather only to retrieve its text.
  This has indeed turned out to be QSqlQuery::lastQuery(), and I have now marked this question as Solved. Thanks all.

• 

  Unsolved Centering QComboBox in table cell
  • gabor53

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  @gabor53
  easiest would be to wrap the combobox within a separate QWIdget with a layout where you add the combobox centered.

• 

  Unsolved Custom view - problems with selection
  • Kicer86

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  Did you already saw the using a selection model part of the Model View Programming chapter ?
  There's also the Model View tutorial that could be of interest.

• 

  Unsolved Parent child relationship!
  • Lasith

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  @Lasith Not really clear what you want to do.
  Do you mean this: http://doc.qt.io/qt-5.9/objecttrees.html ?

  "I want to use an object declared in the parent in the child! How can I achieve this?"
  Why? A child should not know any implementation details of its parent. Child can emit signals which parent can use to do what ever is needed. This way child does not depend on parents implementation details.
  See https://en.wikipedia.org/wiki/Loose_coupling

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  Unsolved serial communication
  • Rameshguru

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  @Rameshguru

  It has nothing to with clicking a button

  When Data signal comes
  you do
  QByteArray str; // this should live in class
  str.append(serial->readAll()); // append to buffer for each read

  when str.size() is big enough that you know all data have been read, you can then look at the data.

  There is NO WAY to make sure that it only takes 1 serial->readAll()
  to get all data.

• 

  Unsolved How to open more than once SerialPort
  • erytcg

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  @erytcg You get double numbers as hex?! Is the double format used by this device clearly specified? I mean, you need to know how to convert those hex strings to doubles for that you need to know the format and byte order.

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  Unsolved This application failed to start because it could not find or load the qt platform plugin "windows".
  • small_bird

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  @laserdyne.rd it's all in the docs, the whole deployment process is described, and all the many ways in which it can/ should be done. Following that will not break your dev installation, and it will work for users who have no Qt installed, too.

  Yeah, though, I definitely agree the error message could be more informative - feel free to open a suggestion on Qt bugtracker or mailing list.

  I've also just noticed the deployment guide is slightly outdated (still mentions Angle as default config option on Windows, which is not true anymore).

• 

  Solved How to custom QComboBox
  • ivanicy

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  @mrjj
  Hi,

  there i have not assign any value to font item so...

• 

  Unsolved Desktop application with qml
  • Tirupathi Korla

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  Yes, you sure can - I use c++, quick, widgets, controls2 & charts for a very nice combination.

  Self-critically... my code ranges from some very neat and performance oriented in some places, some not so much to nearly adverse in others... I still cannot believe how hard I push this.

  Some of the abuse I do would certainly just not happen in .NET or Java land... even the scripting in my QML files is quicker to code and execute due to QT's declarative and event driven focus... no callbacks or timeouts mean only work that has to be done - is done - and only as required. I am still only on a single thread (not including any engine threads not started my me explicitly).

  I am very soon to cut my c++ engine out of my gui thread - I've almost reshuffled my codebase to have only QML exposed objects in the main thread - as of now everything happens on the GUI thread and it's truly stupid the amount of work I can do before seeing frames dip. I'm at that stage now but it really boggles my mind that I can do this on such low hardware.

  As usual there are bits you have to do yourself - there is a surprising amount you do not. You do, however, need to know something exists before you can take advantage of it... search the example applications for QML and you'll get some idea what is canned/off shelf http://doc.qt.io/qtcreator/creator-build-example-application.html

  Being declarative and event driven is a big plus. I'm frequently uncovering greatness hidden inside States, Transitions and Behaviors. I just discovered http://doc.qt.io/qt-5/qml-qtquick-rotationanimation.html today... still being surprised with just how much script work I can ditch in favor of using these components instead. Much easier to maintain and often similar or better performance.

  I find working with the system often performs quicker and subtle things can make a big difference - it helps to be aware of http://doc.qt.io/qt-5/qtquick-performance.html - some very simple practices can help a lot.

• 

  Unsolved How to create a class based on QSettings
  • KelvinSP

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  I have a class name document_session as instance:

  /// Header pointer & static: QPointer<DOC> DOC::_self = 0L; DOC *DOC::self(QObject *parent) { if (!_self) _self = new DOC(parent); return _self; } void DOC::setValue(const QString name, QVariant data) { QSettings session_s(QString("OasiClub"), QString("OasiEditor")); session_s.setValue(name, data); } QVariant DOC::value(const QString name) { QSettings session_s(QString("OasiClub"), QString("OasiEditor")); return session_s.value(name); } /// after read e write: const int uservoice = DOC::self(this)->value("MyVoicePref").toInt();

  sample:
  https://github.com/pehohlva/QOASIS/blob/master/src/app/doc_session.cpp
  https://github.com/pehohlva/QOASIS/blob/master/src/app/doc_session.h

  https://github.com/pehohlva/QOASIS
  https://sourceforge.net/projects/oasidoc/

• 

  Unsolved Can QChart draw spectrogram graph,like QWT or QCustomPlot?
  • enhao

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  @enhao

  I think you want Qt Data Visualization rather than QChart.
  Please see here.

• 

  Unsolved Can't get OpenGL version higher than 1.1 on some Win10
  opengl angle 5.6 • • L_Raiz

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  It's unlikely but not impossible however that would be really old hardware.

  What are the specs of the machine you have that situation on ?

  Note that you should also ensure to have proper graphic card driver installed.