C++ Gurus

@AnneRanch To make your code work, you need to do the right things right. I don’t know exactly what you want to achieve. How your menus should look like. Draw them on a sheet of paper and post a photo. Your issues are not related to understanding “connect”. Your connect statements are syntactically correct, meaning you are doing it right. But you want to connect signals from objects in a nested container all to the same slot. So the slot has to know, who fired the signal. That’s where the drama starts. Why hide information at one place by architecture, so you have to dig it out on the other end, in the slot. Why not write a slot or a lambda for each action you want to connect to? Your issue is in the loops around nested containers, not in “connect”. I haven’t seen a use case that requires such a complicated structure. Maybe it’s necessary in your case. Let us know. Tell us why. You are not handling the structure well, otherwise you wouldn’t connect to a nullptr. If you want to fix your code, this is where to look.

Already asked and answered here: https://forum.qt.io/topic/154053/connect-won-t

@Axel-Spoerl Yeah, but if I move it back it gives the runtime error :) . I will try some stack trace and posted here. Also, I will try changing the name of the function as suggested by the remaining binary artifacts idea.

@AnneRanch said in connect won't...: Here's your problem: QObject::connect(QAction, MainWindow_Bluetooth): invalid nullptr parameter The array you use for the connect statement isn't populated properly. At this location: connect(subAction[index_sub] , &QAction::triggered, this , [=]() { this->process_TEST() ;}); ...you have a nullptr in subAction[index_sub]. That's probably a result of the somewhat unusual approach to store actions in an array.

@SGaist Many thanks, I must have missed that one!

@AnneRanch but I am unable to add "check box" to any of them QAction *action = submenu[index]->addAction("Some text"); action->setCheckable(true); adds an action with text Some text and sets it to have a checkbox.

@AnneRanch You may have been trying to do what I did some time ago, but discovered it does not work so is not allowed in Qt. If you have a sub-menu on a menu --- i.e. the menu has that > you click on to "slide out" the sub-menu --- then although Qt allows you also put a checkbox on the parent menu item which has the > slide-out it actually does not work correctly for checking the box, and cannot be made to do so. Do not try to put a checkbox on a menu item which has a child menu slide-out.

@AnneRanch said in Passing a value to slot...: Minor detail; you example is missing the closing "}" - but the compiler catches that, no big deal. You are correct, my bad. I just type these examples in, my eyesight is not what it used to be! (I believe) I have corrected both my previous posts to have that missing }.

@AnneRanch said in Whar is this error saying?: Thanks , I wad actually triggering on wrong action before. I guess I will never know why I how to read the "() " error to correct my code. The compiler is actually exactly telling you why it has a problem with the (missing) brackets, I'll quote the part: cpp-compiler said in mainwindow_Bluetooth.cpp error: expected '(' for function-style cast or type construction it thinks your bool is an attempt of you to cast something to an boolean and it thinks the silly programmer forgot to add the bracket and the actual variable that is supposed to be cast. something like this: int a = 0; auto b = bool(a); or in your particular case: void triggered(bool variable) { qDebug() << variable } .... int a = 0; triggered(bool(a)); The compiler doesn't know that function style cast do only the other people, true c++ programers don't use it at all.

FINALLY... here a current WORKING as expected - both menu and submenu have check boxes and only main menu has "arrows".... Unless there are objections I am going to clean up the worthless code... Thanks foe sticking with the problem... mainAction[index_main] = m_ui->menuWindow_cpntrol->addAction(list[ index_main] + " #" + QString::number( index_main)); mainAction[index_main]->setCheckable(true); //adds arrows mainAction[index_main]->setMenu(tempmenu); subAction[index_main] = tempmenu->addAction(list_hcitool[ index_main] + " #" + QString::number( index_main)); subAction[index_main]->setCheckable(true);

@AnneRanch said in QMenu C++ code help: That is the issue - how to change "checkable" property when there is access only to QMenu. That is what you wrote. So I took the time to answer it exactly. You cannot get directly from a QAction * to the QMenu you put it on, unlike the other way round which you asked and is answered. However, you can use QList<QObject *> QAction::associatedObjects() const from a QAction and you should find the QMenu it has been added to among them. And you add submenus to a menu. Which answers the new question.

@AnneRanch said in QMenu - submenu arrow removal: my OS is Linux Same here. Start spectacle, define a delay of e.g. 10s, choose a rectangle or select "Active Window". Then you have 10s to bring the menu up and keep it. But I assume you won't do it anyway, as usual.

@AnneRanch The recommended way is: connect(subAction[index], &yourClass::triggered, this, &thisClass::testSlot);

@Chris-Kawa said in Process Protection: If what you're saying was universal the entire gaming industry wouldn't exist and wouldn't be the biggest entertainment medium in the world as it is. I'd like to point out that there is no conflict in that world and what I wrote. See this description; https://www.theverge.com/2021/9/23/22690670/epic-eac-anti-cheat-linux-valve-steam-deck-support-games EasyAntiCheat is a company that doesn't focus on process protection in the way that OP asked. For starters it requires kernel support.

@Chris-Kawa Unluckily, not, Chris. A, B and X are downloaded. If I can rebuild A and B, I will be able to build A, B and X to FOO easily. One way out may be to exclude X from the build with '-Wl,--exclude-libs, X', but break X and add its obj files to FOO while keeping A and B

@Sachin-Bhatt I had to look up what "dynamic programming" is! They like their labels for things, don't they? Am I missing something, or is this real easy? You start by setting a variable for the longest subsequence to 0. You count from left to right while the numbers increase. So for 10, 22 and then 9 the longest so far is 2 (10, 22), terminated by 9 (because it is less than the preceding 22). You note that 2 is the longest so far, because it is more than 0, and so update the count variable. You know that you can resume looking from the 9. You encounter 9, 33 and then 21, 50, both terminated by smaller numbers, and those are also of length 2, no better then before. Finally you meet 41, 60, 80, terminated by end of input, that is length 3, and so is the highest. So that is what you return....

@prasad2023 said in Cross platform compatible GUI application with C++ core logic: Are qt gui and c++ backend are right technologies to develop such application? Obviously, you will get a "yes" here. There is a very large number of applications written using Qt that are similar to what you describe. With "similar" I don't specifically mean trading applications, I mean professional desktop applications that use high-volumes of data and aim at a great user interface. @prasad2023 said in Cross platform compatible GUI application with C++ core logic: afaik, qt apis are wrappers around native os apis. will it impact performance? This is not a good description. Qt is a toolkit and covers a LOT of ground and provides a very large number of features. Any other toolkits, including the ones from Windows or Mac will basically have the same approach that Qt has for most of these features. Therefore it won't be slower than those. The term "wrapped" I have mostly seen used for widgets. The point there is that a Qt app can look identical to a native Windows or Mac application. If you so choose. I don't think you need to worry about that being slow. @prasad2023 said in Cross platform compatible GUI application with C++ core logic: is there any alternative for c++ for this requirement. I don't think there is anything out there that will be good enough for such an application.

@Axel-Spoerl no, not at all. Maybe some code will help. I have a struct: struct Equipment { Q_GADGET QML_STRUCTURED_VALUE QML_VALUE_TYPE(equipment) ... and I maintain a list of these in a model. In my QML, I have a ListView that accesses the model, and furnishes the contents to a delegate that eventually gets down to: equipmentModel.processSpaceAssignment(vspInModel, spaceUuid, checked) where vspInModel is an instance of a subclass of Equipment. There's some rather complex work that needs to be done, so I didn't want to try to implement it in JS. The C++ function signature is: bool EquipmentModel::processSpaceAssignment(Equipment equipment, QUuid spaceUuid, bool add) So, my original question was, is this equipment/vsp object passed by value in this case?