General and Desktop

@shreya_agrawal The issue was solved. Follow these steps: Add this line in the /etc/sysctl.conf file and then save the file: kernel.perf_event_paranoid = -1 Earlier, the perf_event_paranoid was set to 4, which was the cause of the error. -1: Allow use of (almost) all events by all users 0: Disallow raw and ftrace function tracepoint access 1: Disallow CPU event access 2: Disallow kernel profiling Then, apply the changes by running the following command: sudo sysctl -p

@JonB Dear, I've figured out the issue.. It is the parameter parent in the constructor QDialog(QWidget *parent = nullptr, Qt::WindowFlags f = Qt::WindowFlags()) matters. I used it as nullptr. After passing the pointer of the main widget to QDialog, it behaviours as the same as my desire. However, it is true that the widget does not receive any events, such as QEvent::WindowActivate :-)

@Christian-Ehrlicher alright I just decided to forbid table view sorting for the python side. It is strange that C++ side works and Python fails. But there are some chances that the reason of that is my personal additions so I will take some time to investigate it.

@jdent Please append a qDebug() statement to each of your append/insert code fragments showing what you are comparing which you say changes/does not change.

@rahmanih said in Can't build QT6 on Windows using MingWin54: Git BASH to run the build command. You must not have any MSYS related stuff in your PATH - otherwise the build tools might pick them up (due to same name) and it will fail. You can see the problem already in your first output if I'm correct: "@C:/temp/qt6_min/qtbase/src/3rdparty/libjpeg/JpegPrivate_syncqt_args" - the forward slashes (but I might be wrong)

I used Qt Maintenance Tool, and after 2 x 6.2 GB downloads (the first one ended abruptly while I wasn't watching), and some non-obvious-to-a-beginner hurdles to switch to new toolset, I fixed my problem. Qt 6.6.3 doesn't have the bug.

Please read the docs of submitAll(): "In OnManualSubmit, on success the model will be repopulated. Any views presenting it will lose their selections."

@ngocanhnu I don't think that's quite the same problem, but thank you.

@jdent You do not need to drop down to accessing the model directly via QModelIndex and setData(). You can do it via the QSqlRecord. After you went rec.setValue(1, val); you need to call bool QSqlTableModel::setRecord(int row, const QSqlRecord &values) to transfer the altered in-memory rec to the model: QSqlRecord rec = tm.record(0); QModelIndex idx = tm.index(0, 3); qDebug() << rec.value(3).toString(); qDebug() << idx.data().toString(); auto val = rec.value(3).toString(); val += "###"; rec.setValue(3, val); qDebug() << rec.value(3).toString(); qDebug() << idx.data().toString(); tm.setRecord(0, rec); qDebug() << rec.value(3).toString(); qDebug() << idx.data().toString(); This shows the underlying model altered after the tm.setRecord(0, rec); statement. You can then commit() or whatever if you wish. record() generates a copy of what is in a model row. setRecord() is required if you alter that and want to write it back to the model row.

@gumtown Plenty of questions/solutions to this from Googling. See e.g. https://stackoverflow.com/questions/60989706/qt-bluetooth-stuck-when-connecting-to-classic-bluetooth-device You are trying to run your software as a non-root user. Try sudo setcap 'cap_net_raw,cap_net_admin+eip' yourapplication

@wujie If your situation is " the same as yours [OP's]" then you are showing too many points, as several responders said. If you want to "add a batch of many items" you could temporarily detach the changed() slot as the OP wrote, or call blockSignals(). Having said that I'm not sure what the OP's actual issue was. While it is true that changed() would be called many times it is not true that each of these causes any visible update to the view. The view is only visually updated the next time the event loop is entered, at which time it should see so many updates that it does not do each one at a time but rather just decides to redraw the view a single time.

@JonB Thank you for your reply. I will mark this thread as solved and try it out, thanks. Have a good one :)

@jdent No, there is no findId() or similar method, else you would see it on https://doc.qt.io/qt-6/qsqlrelationaltablemodel-members.html. If you wish to find it efficiently, e.g. if you have a thousand records in memory and don't want to search them sequentially each time, you can add a QSortFilterProxyModel on top of your QSql[Relational]TableModel, or sort the underlying model. Then if you set the sort to be by primary key you know the rows are in ascending primary ley order so you can use a binary search to find a given ID very fast. You do not need to use such an extra QSortFilterProxyModel for your view, you could just add it for the purpose of searching. You might get away without bothering to add one. Without a sort the statement will be SELECT * FROM table, with no ORDER BY clauses. Many/most SQL databases will deliver rows in primary key order when no ORDER BY is specified. If your ID column is the primary key they will appear in ID order (and so can be binary searched). However I would regard this as "fragile" as it relies on underlying SQL database behaviour. You could also impose a QSortFilterProxyModel and use its setFilter("id = ...") to pick out a given ID. However this does its work by issuing a SELECT ... WHERE id = ... against the table, not be searching rows already read in, and I don't think this is what you are looking for.

You should ask whoever supplied the Qt libraries in the Windows cross-compilation environment on Linux that you are using. If you constructed this environment yourself then it is up to you to build Qt with relevant options.

@Christian-Ehrlicher The OP seems to want to add a series of consecutively numbered items to a list (the the number is "id"), remove arbitrary items, and have the items remaining still be consecutively numbered. Iterating over the list is solution to the question posed, but I think this is an XY Problem. This numbering: repeats information that is available simply from the index in the list, negates the typical purpose of an immutable identifier, and enforces a common anti-pattern that monotonically numbered items need to be/stay gap free, in this case causing more busy work.

@jdent I am pretty sure this is it!!

@Christian-Ehrlicher Thanks!!

@AnneRanch said in how to use "cascaded connect "?: How do I code the "child class" to use the "parent class " "connect"? After reading this again... is it about INHERITING signals/slots from "parent" or a base class? Your "parent" as you call it, has a signal ping() and is connected to a slot in widget B... and now you want to have the same connection to B in a child QObject of A? That's not possible. Parent/Child are two different QObjects and you have to connect each independently. You can inherit signals from a base class, but class inheritance is not the same thing as a QObject Parent-child relation....

@JonB said in QString Turkish Character Problem: how ridiculously complicated language encoding is in C++! It's more a windows/msvc problem using anything else but utf-8 for the source files and even during runtime.

Please provide a minimal, compilable example of your problem. No designer stuff needed to reproduce this issue.