Language Bindings

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  Unsolved Which is Better C or C++?
  c++ • • Mayankjain

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  @Mayankjain said in Which is Better C or C++?:

  my carrier

  What would be your carrier? What kind of software are you going to develop? Because programming language depends on use case. For example: if you're going to contribute to Linux kernel then learn C, if you want to develop GUI applications learn C++, ...

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  Unsolved glitch in javascript bindings
  • skylendar

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  @skylendar hi,

  Can I ask why are you declaring the constructor of z with Q_INVOKABLE and creating an object in the JS engine ?

  QJSValue ZObj = newQMetaObject(&z::staticMetaObject); globalObject().setProperty("z", ZObj);

  This should not be necessary as you don't need to create the object from Javascript.

  Then the function Test::get()must return a Javascript object wrapping instance of z:

  QJSValue get() { auto x = new z; return jsEngine->newQObject(x); /* or return jsEngine->newQObject(new z);*/ }

  Note that by doing this you avoid memory leak of x because the Javascript engine take ownershipt of the object

  Are you sure you want to create a new instance of z each time you call get() from Javascript ? I mean, this is more a create() function :). Or do you want to "share" an object your class Test. Something like that in javascript:

  var z = new test() var a = z.x z.x.someFunction()
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  QAxServer in Python [PySide] [PyQt]
  • boattyman

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  Hello,

  I'm facing the same issue.

  Have you solved this problem?

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  Unsolved Q_Property add range macros
  • Vitaliy

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  Hi,

  AFAIK, there's none. You need to implement your own macro on top Q_PROPERTY to do that.

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  This topic is deleted!
  • ASDFG

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  This topic is deleted!
  • Xperia

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  Unsolved C function as QJSValue
  • skylendar

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  So I give up. I'll declare a method instead.

  Maybe in a further version of Qt5.

  Thank you anyway.

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  Unsolved PyQt5 virtual keyboard (TypeError: missing 1 required positional argument)
  pyqt5 virtualkeyboard python3 qt5.5 python • • alekssandrap

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  @alekssandrap
  Hello,

  I found your topic because I am looking for a virtual keyboard for my PUQT5 application.
  So, I found the problem of your error and this is my solution to solve it (maybe that can help some other people) :

  In your pyqtSignal you have to pass an object :
  sigKeyButtonClicked = pyqtSignal(object) #line 9

  sigInputString = pyqtSignal(object) #line 32
  sigKeyButtonClicked = pyqtSignal(object) #line 33

  Then you have just to pass your key and your inputString in the signal emit :
  self.sigKeyButtonClicked.emit(self._key) #line 20

  self.sigInputString.emit("") #line111 in function Cancel in order to avoid an other error

  Don't modify line 71 with lambda as @AlfredoC suggest because you won't be able to get the key pressed.

  That's all :)

  Hope that can help someone else.

  Have a great day

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  Solved Read a specific tag in xml
  • Nathan Miguel

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  @Nathan-Miguel said in Read a specific tag in xml:

  PROGRAM DIRECTORY: E:\Git\Denoiser-Script\QML_C++\build-Denosier-Desktop_Qt_5_12_3_MSVC2017_64bit2-Debug\debug
  XML DIRECTORY: E:\Git\Denoiser-Script\QML_C++\build-Denosier-Desktop_Qt_5_12_3_MSVC2017_64bit2-Debug\debug\sysinfo\system.xml

  In your code extract you have hard coded the path and with you output it should be:

  QString systeminfo::getCpuName() { QString rootDir = qApp->applicationDirPath(); // QDir::currentPath() != not application path QString xmlDir = "/sysinfo/system.xml"; QDomDocument docxml; QString test; QFile xmlread; xmlread.setFileName(rootDir+xmlDir); test = "head"; if (xmlread.open(QIODevice::ReadOnly)) { QXmlStreamReader reader(&xmlread); if (docxml.setContent(&xmlread)){ //Open xml with success test = "xml loaded with success"; //Read specifc tag xml auto nodes = docxml.elementsByTagName("cpuname"); for(int i = 0; i < nodes.count(); i++) { QDomNode elm = nodes.at(i); if(elm.isElement()) { test = QStringLiteral("%1 = %2").arg(elm.toElement().tagName(), elm.toElement().text()); } } } } return test; }

  ==> my output with this code and your XML document is:
  

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  Unsolved Generating bindings for other languages
  • semtexzv

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  Hi @semtexzv, and welcome!

  @semtexzv said in Generating bindings for other languages:

  ...mainly utilize Rust language.

  Have you seen the Rust-Qt project? https://github.com/rust-qt

  could the shiboken generator used to generate bindings for other languages in custom format ?

  I'll leave this question for someone else who has experience with Shiboken. But if you want to check yourself, this is a good place to start: https://blog.qt.io/blog/2018/05/31/write-python-bindings/

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  Unsolved I want to good tutorial or book on PyQt
  • Qt Enthusiast

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  I just published a PyQt5 book:

  Even Phil Thompson, the creator of PyQt, read it and says it's "very good". It saves you a lot of time when learning PyQt. It's the resource I wish I had had when I was getting started.

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  This topic is deleted!
  • Hitokage

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  Unsolved Pysyde/QTableView: openPersistentEditor works only once?
  • dammilo

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  @SGaist sorry if I'm so late, I wasn't notified about your post.
  I'm using PySide 1.2. I am working inside 3dsmax 2017 and I have to use what Autodesk provides me - I have no choice about this.

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  Unsolved Dynamically call methods from a scripting engine using QMetaMethod and QVariant.
  • French Paragon

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  Unsolved how can I join and run a program when starting application?
  • Nathan Miguel

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  @Nathan-Miguel

  As I said/suspevted:

  You show us the code of your Qt application, which does not create the file, so it does not help.

  Nowhere do you you show whatever code does create the file, so since we cannot see that we cannot advise what it is you need to do.

  I wrote above:

  Are you now talking about what the current directory will be for the main.exe you run from your Qt program (perhaps because it creates systeminfo.txt without specifying a path)??

  but you didn't reply to that. If you want help, you'll need to provide information.

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  Solved how can I use c ++ not qt QUICK / QML?
  • Nathan Miguel

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  @sierdzio said in how can I use c ++ not qt QUICK / QML?:

  engine.rootContext()->setContextProperty("cpuname", &CpuName);

  its works tnks

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  Solved How to I get cpu description and cpu name
  • Nathan Miguel

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  Something like lspci -vnn | grep VGA ?

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  Solved Emitting and handling signals with GoLang and QML respectively.
  • Nikhilesh N

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  @SGaist Thank you, Samuel. I will definetely try it out.
  Marking this topic as solved.

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  Unsolved Qt and cmake issue
  • jpitz3131

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  Unsolved Compiling static Fortran library Qt
  • Jakub Srna

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  Guess that this is caused by the set flags.

  I don't know.

  Can I include that somehow as I know it optimizes the code more?

  Fortran uses C-linkage so any linker should be able to manage it.
  Note that fortran mandates decoration of the function names itself, because reasons. So if you have:

  subroutine dummy() end subroutine dummy

  This is seen by the linker as if it was defined as void dummy_().
  If you intend to call fortran from C, you must provide the proper declarations for the compiler in your C code, they can't be deduced automatically.

  When I use either gfortran or ifort in my code and I'll try to do the cross compilation. Will the fortran part of the code run flawlessly on Mac or Linux?

  As long as you configure the compiler properly, you can treat fortran code as any other C code, so it should work fine, yes.

  Tangent:
  gfortran, I believe, still transpiles the fortran source to C and then runs the C compiler on top of it. In the end why should anyone invest time into keeping a real compiler for a zombie language up to date ...

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  Unsolved Qt GUI with Eclipse c++
  • GastonMelo

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  I'd recommend reading the Qt5 version: https://doc.qt.io/qt-5/signalsandslots.html

  @GastonMelo You really should take the time to go through Qt's documentation. It's full of tutorials, getting started guides and it also explains all the core concepts provided within the framework.

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  Solved Shiboken - Building bindings with headers in subfolders
  • snkaupe

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  Hi,

  Thanks for the feedback ! Can you post the link to said patch ?

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  Unsolved Using QImageCleanupFunction with PySide2
  • laan

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  Hi,

  Good question. What does your function look like ?

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  PyQt5: Invisible items in a QML ListView (perhaps a bug?)
  • MazeChaZer

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  @JonB Thanks

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  Unsolved QDateTimeAxis not shown in QChartView
  • Zeeshan Mehmood

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  Solved Python/PyQt/PySide - How to add an argument to derived class's constructor
  • JonB

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  Just to close this up. Although I posted this question here, to the the PyQt mailing list and on stackoverflow, since I never got an actual answer as to how to write the derived class's constructor to accept the new positional argument while retaining all the existing overloads, in the end I have actually gone for a named argument:

  class JListWidgetItem(QtWidgets.QListWidgetItem): def __init__(self, *args, value: typing.Any=None, **kwargs): super().__init__(*args, **kwargs) # optional `value` member, passed in as `value=...`, stored in data(Qt.UserRole) # this is a common thing to want, cf. `QComboBox.itemData()` if value is not None: self.setValue(value)

  and caller goes e.g. JListWidgetItem("text", value=1). Some people have said this is the more "pythonic" way, who knows, but at least it works! Thanks to all.

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  Unsolved PySide2 - How to prevent crashing when running multi-threaded calculations then plotting the emitted results
  • AndrewF

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  The first thing you should do is to make Worker inherit both QObject and QRunnable. QObject must come first. Making it a separated class and calling signals on it is wrong. Signals should be emitted from within the class that defines them.

  Another thing is that you don't set your worker to auto delete so you will end up eating lots of memories depending on how many times plot is called.

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  Unsolved Web Assembly and decalarative-camera example.
  • Julian Guarin 0

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  @Julian-Guarin-0 said in Web Assembly and decalarative-camera example.:

  So I guess you are right. Does this confirm what you did see?

  as i said, i didnt see anything ;)
  But the configure clearly shows that you might only be possible to play sound files, i don't know if thats really true though for QtWebAssembly.

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  This topic is deleted!
  • thippu

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  Unsolved Pyside QLineEdit entering data from right-to-left
  • Joel Graff

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  @aha_1980 said in Pyside QLineEdit entering data from right-to-left:

  @Joel-Graff your example does not look like valid float number.
  Do you need exponential format? I'm not sure, if QDoubleSpinbox provides that, otherwise it would be first choice for that task. For the line edit, you could use input masks or hook up an own 'correction function' on every key press.

  It is, in fact, a valid float. It's called a "station" where 1 station = 100 feet. Thus 999 feet = 9.99 stations, which is commonly annotated 9+99. It's really just a length. The example I gave is actually the input mask I'm using - sorry for the confusion. The problem is, the input mask doesn't really fill out the required placeholders correctly. That is, if I create an input mask that reads:

  '00009+99.00;_'

  I would expect it to show

  ____0+00.__

  as a default. Of course, it doesn't, and I admit, I don't really know much about input masks in Qt.

  Since I can't rely on the input mask to control the data entry, forcing it to enter data from the right (and push the characters to the left) seems the next best option. It's a fairly common data entry technique - I've seen it even in very old terminal-based systems. I was hoping I didn't have to craft my own callback to manage it.

  Thanks anyway. :)

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  Qt compatibility with VHDL source codes??
  • Pallu

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  @aha_1980 thanks.
  They can add it to the gallery if they like, but the plugin is still work in progress.

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  How to make QAbstractTableModel 's data checkable
  • redstoneleo

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  a minimized example

  import sys from PySide2.QtWidgets import * from PySide2.QtCore import * from PySide2.QtGui import * from PySide2.QtSql import * class MyModel(QSqlTableModel): def __init__(self, parent=None): super().__init__(parent) self._checked = [[False for i in range(self.columnCount())] for j in range(self.rowCount())] def rowCount(self, parent=QModelIndex()): return 2 def columnCount(self, parent=QModelIndex()): return 3 def data(self, index, role): if (role == Qt.DisplayRole): return "Row{}, Column{}".format(index.row() + 1, index.column() + 1) elif role == Qt.CheckStateRole: print('data(self, index, role)-------------', index.data()) return self._checked[index.row()][index.column()] # show CheckBox's check state return None # be sure to return super().data(index, role) if worked with QSqlTableModel; def flags(self, index): return super().flags(index) | Qt.ItemIsUserCheckable def setData(self, index, value, role): # implement the setData() method to allow for the check state to change if role == Qt.CheckStateRole: print(value) self._checked[index.row()][index.column()] = value # CheckBox's check state depends on the value return True # Returns true if the value could be set return False # be sure to return super().setData(index, value, role) if worked with QSqlTableModel;Returns true if value is equal to the current value. However, the value will not be submitted to the database.; if __name__ == '__main__': app = QApplication(sys.argv) tableView = QTableView() myModel = MyModel(None) tableView.setModel(myModel) tableView.show() sys.exit(app.exec_())
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  Solved QIODevice::read (QProcess): device not open
  • FoxBandyKoot

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  **My first problem has been resolved, so I will close this, and open a topic for my new problem.

  For future people who come to this topic : The solution for "Device not open" was to use "start function" instead of "execute function".

  Thank you people for helping me.**

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  Unsolved What's the state of perl bindings for Qt5
  • daveh

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  Did you also check this https://cgit.kde.org/perlqt.git ?

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  Unsolved How to install and use pyqt5
  • aidanikuz

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  @aidanikuz please watch following video to install and use pyqt5

  https://www.youtube.com/watch?v=yqHiOesB-nI

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  Unsolved Garbled when compiling JAVA
  • ArcherLiang

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  yes.
  I guess it might be encoding problem . I set the UTF8 encoding in the options,but it didn't solve the problem.
  Platform:
  QT version :Android for armeabi-v7a (GCC 4.9, Qt 5.9.3 for Android armv7)
  OS: windows 10
  Qtcreator version: 4.7.2
  Compilers: Android gcc arm-4.9, JDK1.8
  Thanks.

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  Unsolved Use Qt for gui frontend for Java jar
  • blue34

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  @blue34 I haven't tried grpc before. It uses protocol buffers though which I have used and aren't a bad way of doing things.

  I've never much cared for RPC mechanisms but whatever is easy for you to get implemented in the C++ side and the Java side is a decent way to do things. :)

  Like I said I always go the other way... native c++ library with the front end in java (android) and ios (objc). I've been trying out djinni for that lately and it makes the jni and what not nice and easy. Wrong direction though so that won't help you out much.

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  Unsolved Can C functions send data to QT Slots in QT5.7 ?
  • vivekyuvan

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  @vivekyuvan

  As @sierdzio already said, you cannot directly call C++ from C, and therefore you cannot use Qt.. But it is possible to write a wrapper, like discussed here: https://stackoverflow.com/questions/3583353/calling-c-class-member-function-from-c-code

  From within the C++ class, you can access all kind of Qt stuff again.

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  Unsolved Slots execution order and catching menu/action clicks
  • voltron

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  I can't explain difference between case 2) and 3).

  However, what you see in 1) is that signal-slot connections are always executed in order in which connections were made (hint: don't depend on this, though). So, when you connect in your plugin, you always do it after main program already had connected it's signals and slots - and thus your slots are executed after main program's, too.

  Then in 3) you get immediate execution because (probably) there was no connection made in main program for that particular triggered() signal - you are first in queue.

  Why 2) and 3) show different behaviour - I don't know.

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  Unsolved How to pass string value from dialog to mainwindow
  • dancaer69

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  @dancaer69
  @SGaist is (of course!) right. To expand on what he says:

  "use signals and slots": in the dialog, use emit() to raise a signal once the value has been set. In your main window module, use connect() to register a slot defined there which will receive the string passed in the signal by the dialog.

  "have your dialog provide getters to retrieve the values you want": from main window create your dialog instance, then execute it, then while the dialog variable is still in scope you can call functions in it to retrieve values:

  dlg = QDialog(self) if dlg.exec(): value = dlg.someFunction()

  In this case, do not set the Qt "auto delete dialog object after executing" flag (it is not normally switched on).

  Either method is acceptable, with pros & cons. Both are preferable to using a "global variable" (which you will find pretty difficult/non-obvious in Python anyway).