On first post, in Topic Tool button, you can mark solved

I cant explain it. seems not right. Also if it triggers the signal and goes into the
insertRow function then unless its wrong model or wrong Tree, it should
work.
Have you tried add a line in Designer and check if the Tree you talk to have 1 item?

class InterfaceRender : public QOpenglFunctions, public QOpenglWidget {
Q_OBJECT
public:
//The pointer to the TreeWidget
QTreeWidget* TreePointer;

//The update function
void PainGL()override {
  //And here insert one row per frame (only to test my case) with my own data
  //Cast the user data to anything, I don't care
    QAbstractItemModel* const mdl= TreePointer->model();
     const int rowCount =mdl->rowCount();
     if(mdl->insertRow(rowCount)){
        qDebug("Row Inserted!");
        if(mdl->setData(mdl->index(rowCount,0), UserData->name))
           qDebug("name Written");
        if(mdl->setData(mdl->index(rowCount,1),UserData->description))
           qDebug("description Written");
     }
  }
}

Explain me, why I can't use this? Imagine that the pointer exists (is set at any point of the program). If you try something like this, the QTreeWidget won't show ANYTHING, it seems that is empty... That was the main problem.

Also when you say AFTER the app.exec(), we agree it just means
when app is running ?

Why cant u just emit signal from PaintGL() ?
Why must it be function call?

But unless there are multiple threads involved, calling the function directly should do it.

since InterfaceRender is also a widget, if u add Q_OBJECT it can emit signals.

¨so

class InterfaceRender : public QOpenglFunctions, public QOpenglWidget {
Q_OBJECT
public:
void PainGL()override {
  //And here insert one row per frame (only to test my case) with my own data
  emit insertRow(&cubeWithParallaxMapping);
}

just define it as a signals in .h

and in

class TreeNodesManager : public QWidget {
Q_OBJECT
public slots:
  void InsertRow(void* UserData)   {...]

then connect them and it should work.
connect(InterfaceRender, SIGNAL(InsertRow(void* )),TreeNodesManagerPTR, SLOT(InsertRow(void* )), Qt::QueuedConnection );

Note there might be issue with the cubeWithParallaxMapping since its a void * as QueuedConnection
wants to be able to copy it

At this moment of the discussion, I have a TreeNodesManager.ui with the correspondent .h that has the function InsertRow(void* UserData), and inside the ui file I have the QTreeWidget pointer.
In the other side I have my InterfaceRender.h that inherits from QOpenglWidget & OpenGL and if I want to test something: I override the PaintGL() function and put this

class InterfaceRender : public QOpenglFunctions, public QOpenglWidget {
public:
 //THE CLASS IS NOT COMPLETE
void PainGL()override {
  //And here insert one row per frame (only to test my case) with my own data
  PointerTo TreeNodesManager->insertRow(&cubeWithParallaxMapping);
}

}

And here my class that manages the QTreeWidget, keep in mind that the QTreeWidget is in the UI file:

class TreeNodesManager : public QWidget {
public:
  
 TreeNodesManager(QWidget* parent), QWidget(parent) {
    ui->setupUi(this);
    ui->treeWidget->setColumnCount(2);
    ui->treeWidget->setHeaderLabels(QStringList() << "Name" << "Type");
    
  }
  //And the fantastic function
  void InsertRow(void* UserData) {
    //Cast the user data to anything, I don't care
    QAbstractItemModel* const mdl= ui->treeWidget->model();
     const int rowCount =mdl->rowCount();
     if(mdl->insertRow(rowCount)){
        qDebug("Row Inserted!");
        if(mdl->setData(mdl->index(rowCount,0), UserData->name))
           qDebug("name Written");
        if(mdl->setData(mdl->index(rowCount,1),UserData->description))
           qDebug("description Written");
     }
  }
}

Look the last function insertData, ALL THE qDEBUG is called.
Please explain me how can I insert data AFTER the app.exec() is called (at runtime). I try this in the PainGL() function that is called one time per frame and it doesn't work

Hi
The button clicked() is a signal ánd is called internally by
emit Clicked()
one dont call like a normal functions as its a signal and emit must be use.

Not sure you can emit it from outside and why would you ?
I think its possible with meta calls but i never tried.
You can call it like

QMetaObject::invokeMethod(addTreeBtn, "clicked",
   Qt::QueuedConnection,
   Q_ARG(QString, "p1"),
   Q_ARG(QString, "p2"));

But it will say
QMetaObject::invokeMethod: No such method QPushButton::clicked(QString,QString)
Candidates are:
clicked(bool)
clicked()

Only
QMetaObject::invokeMethod(addTreeBtn, "clicked", Qt::QueuedConnection );
will work.

Clicked() do not have parameters so you cannot add new ones as then
the buttons real clicked() could not work. How would it get the parameters?

Can I ask what you are trying ? it seems sort of reverse.

If you want to be able to call it both from a function and use with a button, simply use
a normal slot function and not a lambda. Then you can both call the slot or let a button do it.
But i repeat. The clicked() signal has no parameters and you cannot just add some.

so the void insertRow(QAbstractItemModel* const mdl) seems like a good idea.

Also, if you want to use slot & Signals, the main is not a good place as moc only runs on .h files.
(hax included, see last line)

But since it causing you so much issues there must be something going on we don't see.

i also wondered about

• if you don't insert the elements using the Signal/Slot this does not work

So in what way are you trying then ?

Also all ways are possible

void insertRow(QAbstractItemModel* const mdl, const QString& ColData1, const QString& ColData2) {
  const int rowCount = mdl->rowCount();
  if(mdl->insertRow(rowCount)) {
    qDebug("Row Inserted!");
    mdl->setData(mdl->index(rowCount, 0), ColData1);
    mdl->setData(mdl->index(rowCount, 1), ColData2);
  }
}

class SlotHolder : public QObject {
  Q_OBJECT
public slots:
  void AddRowsWithParam(QAbstractItemModel* const mdl, const QString& ColData1, const QString& ColData2) {
    insertRow(mdl, ColData1, ColData2);
  }
};

int main(int argc, char* argv[]) {
  QApplication app(argc, argv);
  QWidget wid;
  QPushButton* addTreeBtn = new QPushButton("Add Row", &wid);
  QTreeWidget* treeWid = new QTreeWidget(&wid);
  treeWid->setColumnCount(2);
  treeWid->setHeaderLabels(QStringList() << "Name" << "Type");
  QObject::connect(addTreeBtn, &QPushButton::clicked, treeWid, [treeWid]() {
    insertRow(treeWid->model(), "From Lambda", "From Lambda");

  });

  insertRow(treeWid->model(), "FROM MAIN as function", "NO SLOT");

  SlotHolder dummy;
  dummy.AddRowsWithParam(treeWid->model(), "As function call via slot", "YEAH");

  QVBoxLayout* widlay = new QVBoxLayout(&wid);
  widlay->addWidget(addTreeBtn);
  widlay->addWidget(treeWid);
  wid.show();
  return app.exec();
}

#include "main.moc" // HAX TO MAKE MOC RUN ON . CPP run qmake manually

in the main loop of the render for example.

What render do you mean ?

Qt is controlled by events which are distributed with this function
return app.exec(); << loops around here
http://doc.qt.io/qt-5/qapplication.html#exec

So if you mean it only works if you let the the event loop run, you are correct.
if you make a tight for loop and never leave it, it cannot work.

If you create a button

void MainWindow::on_pushButton_clicked()
{
    for(;;);

}

You will have 100% killed the program and it cant move or draw itself.

Also its perfectly fine to show the widget first then add Items.

int main(int argc, char *argv[])
{
        QApplication app(argc,argv);
        QWidget wid;
        wid.show(); // show first

        QTreeWidget* treeWid=new QTreeWidget(&wid);
        treeWid->setColumnCount(2);
        treeWid->setHeaderLabels(QStringList() << "Name" << "Type");
       for(int i=0;i<10;i++){
            insertRow(treeWid->model());
        }
        QVBoxLayout* widlay=new QVBoxLayout(&wid);
        widlay->addWidget(treeWid);

        return app.exec(); // first here it will be drawn anyway
}

Also a slot function is a normal c++ function.
There is no difference.

So if you call it insertRow from somewhere and its not working, its either a
plain bug OR you are blocking the event loop by use for/while statement that
never terminates. ( as VRonin says)

Inserting rows works outside constructors and member functions used as slot.

If you see otherwise, please post the whole code where you call
insertRow and we can try help spot what is going on.

update function

That's too generic.

You only can update the TreeWidget if you insert rows inside Slot/Signal function

Signals and slots are just terms used by moc that then converts them into pure C++. there is no difference between a slot and a normal method/function:

#include <QApplication>
#include <QWidget>
#include <QTreeWidget>
#include <QAbstractItemModel>
#include <QVBoxLayout>
void insertRow(QAbstractItemModel* const mdl){
            const int rowCount =mdl->rowCount();
            if(mdl->insertRow(rowCount)){
                qDebug("Row Inserted!");
                if(mdl->setData(mdl->index(rowCount,0),"Pepedfsdf"))
                    qDebug("Pepedfsdf Written");
                if(mdl->setData(mdl->index(rowCount,1),"Descdfsdfsdf"))
                    qDebug("Descdfsdfsdf Written");
            }
}
int main(int argc, char *argv[])
{
        QApplication app(argc,argv);
        QWidget wid;
        QTreeWidget* treeWid=new QTreeWidget(&wid);
        treeWid->setColumnCount(2);
        treeWid->setHeaderLabels(QStringList() << "Name" << "Type");
       for(int i=0;i<10;i++){
            insertRow(treeWid->model());
        }
        QVBoxLayout* widlay=new QVBoxLayout(&wid);
        widlay->addWidget(addTreeBtn);
        widlay->addWidget(treeWid);
        wid.show();
        return app.exec();
}

My guess is that you are blocking the event loop somehow

void InsertElement() {
   QAbstractItemModel* const mdl= treeWid->model();
            const int rowCount =mdl->rowCount();
            if(mdl->insertRow(rowCount)){
                qDebug("Row Inserted!");
                if(mdl->setData(mdl->index(rowCount,0),"Pepedfsdf"))
                    qDebug("Pepedfsdf Written");
                if(mdl->setData(mdl->index(rowCount,1),"Descdfsdfsdf"))
                    qDebug("Descdfsdfsdf Written");
            }
}

Insert this in any class with an UI file (with the TreeWidget), if you don't insert the elements using the Signal/Slot this does not work

If you try to do this for example in the update

That's just an infinite loop.

Update inserts a row -> the view detects the row change -> the view calls update -> loop

mix the APIs?

You were using the QTreeItem API, I used the QAbstractItemModel one.

I have the conclusion that the QTreeWidget only admit new rows in the constructor

this clearly can't be. QTreeWidget doesn't even know you are in a constructor.

can you try this minimal example?

#include <QApplication>
#include <QWidget>
#include <QTreeWidget>
#include <QAbstractItemModel>
#include <QVBoxLayout>
int main(int argc, char *argv[])
{
        QApplication app(argc,argv);
        QWidget wid;
        QPushButton* addTreeBtn=new QPushButton("Add Row",&wid);
        QTreeWidget* treeWid=new QTreeWidget(&wid);
        treeWid->setColumnCount(2);
        treeWid->setHeaderLabels(QStringList() << "Name" << "Type");
        QObject::connect(addTreeBtn,&QPushButton::clicked,treeWid,[treeWid](){
            QAbstractItemModel* const mdl= treeWid->model();
            const int rowCount =mdl->rowCount();
            if(mdl->insertRow(rowCount)){
                qDebug("Row Inserted!");
                if(mdl->setData(mdl->index(rowCount,0),"Pepedfsdf"))
                    qDebug("Pepedfsdf Written");
                if(mdl->setData(mdl->index(rowCount,1),"Descdfsdfsdf"))
                    qDebug("Descdfsdfsdf Written");
            }
        });
        QVBoxLayout* widlay=new QVBoxLayout(&wid);
        widlay->addWidget(addTreeBtn);
        widlay->addWidget(treeWid);
        wid.show();
        return app.exec();
}

Don't mix the APIs

I don't really understand what I did wrong, mix the APIs? Where? I copy-paste your code and still doesn't work. What should I add in addTreeChild to work? @VRonin, you put the same code as me. I have the conclusion that the QTreeWidget only admit new rows in the constructor, all after this will not display. So if you have any simple code or project to add items (i.e. when you click a button inserts a new row) please explain me how

#include "treenodesui.h"
#include "ui_treenodesui.h"
#include <QStringList>
#include <QAbstractItemModel>


TreeNodesUI::TreeNodesUI(QWidget *parent) :
   QWidget(parent),
   ui(new Ui::TreeNodesUI)
{
   ui->setupUi(this);
   ui->treeWidget->setColumnCount(2);
   ui->treeWidget->setHeaderLabels(QStringList() << "Name" << "Type");
  
   //This is working only in the constructor
   QAbstractItemModel* const mdl= ui->treeWidget->model();
   const int rowCount =mdl->rowCount();
   if(mdl->insertRow(rowCount)){
      qDebug("Row Inserted!");
      if(mdl->setData(mdl->index(rowCount,0),"Pepedfsdf"))
         qDebug("Pepedfsdf Written");
      if(mdl->setData(mdl->index(rowCount,1),"Descdfsdfsdf"))
         qDebug("Descdfsdfsdf Written");
   }
}

TreeNodesUI::~TreeNodesUI()
{
   delete ui;
}
//Take a look at the comments
//IGNORE THE INPUT PARAMETERS---------------------------------------------------
void TreeNodesUI::addTreeChild(Node *node_to_add, QString name, QString description)
{
   QAbstractItemModel* const mdl= ui->treeWidget->model();
   const int rowCount =mdl->rowCount();
   if(mdl->insertRow(rowCount)){
      qDebug("Row Inserted!");
      if(mdl->setData(mdl->index(rowCount,0),"Pepedfsdf"))
         qDebug("Pepedfsdf Written");
      if(mdl->setData(mdl->index(rowCount,1),"Descdfsdfsdf"))
         qDebug("Descdfsdfsdf Written");
   }
}

Header.h

#ifndef TREENODESUI_H
#define TREENODESUI_H

#include <QWidget>
#include <QTreeWidgetItem>
namespace Ui {
   class TreeNodesUI;
}

class TreeNodesUI: public QWidget
{
      Q_OBJECT

   public:
      explicit TreeNodesUI(QWidget *parent = 0);
      ~TreeNodesUI();
      void addTreeChild(Node* node_to_add, QString name, QString description);

   private:
      Ui::TreeNodesUI *ui;
};

#endif // TREENODESUI_H

Source.cpp

#include "treenodesui.h"
#include "ui_treenodesui.h"
#include <QStringList>
#include <QAbstractItemModel>


TreeNodesUI::TreeNodesUI(QWidget *parent) :
   QWidget(parent),
   ui(new Ui::TreeNodesUI)
{
   ui->setupUi(this);
   ui->treeWidget->setColumnCount(2);
   ui->treeWidget->setHeaderLabels(QStringList() << "Name" << "Type");
   ui->treeWidget->setUpdatesEnabled(true);
   //This is working only in the constructor
   QAbstractItemModel* const mdl= ui->treeWidget->model();
   const int rowCount =mdl->rowCount();
   if(mdl->insertRow(rowCount)){
      qDebug("Row Inserted!");
      if(mdl->setData(mdl->index(rowCount,0),"Pepedfsdf"))
         qDebug("Pepedfsdf Written");
      if(mdl->setData(mdl->index(rowCount,1),"Descdfsdfsdf"))
         qDebug("Descdfsdfsdf Written");
   }
  //This is working only in the constructor
   QTreeWidgetItem *treeItem = new QTreeWidgetItem(ui->treeWidget);
   treeItem->setText(0, "Pepedfsdf");
   treeItem->setText(1, "Descdfsdfsdf");
}

TreeNodesUI::~TreeNodesUI()
{
   delete ui;
}
//Take a look at the comments
//IGNORE THE INPUT PARAMETERS---------------------------------------------------
void TreeNodesUI::addTreeChild(Node *node_to_add, QString name, QString description)
{
  //ALL INSERTED HERE WILL NOT WORK (its called in some point of the program, I debug this)
   QAbstractItemModel* const mdl= ui->treeWidget->model();
   const int rowCount =mdl->rowCount();
   if(mdl->insertRow(rowCount)){
      qDebug("Row Inserted!");
      if(mdl->setData(mdl->index(rowCount,0),"Pepedfsdf"))
         qDebug("Pepedfsdf Written");
      if(mdl->setData(mdl->index(rowCount,1),"Descdfsdfsdf"))
         qDebug("Descdfsdfsdf Written");
   }
  
  //Another test
   QTreeWidgetItem *treeItem = new QTreeWidgetItem(ui->treeWidget);
   treeItem->setText(0, "Pepedfsdf");
   treeItem->setText(1, "Descdfsdfsdf");
  //With some probes calling updates functions
   ui->treeWidget->repaint();
   QWidget::update();
   repaint();
   return;
}

ui->setupUi(this);
ui->treeWidget->setColumnCount(2);
ui->treeWidget->setHeaderLabels(QStringList() << "Name" << "Type");

Function Insert item

//I set this item as header in the tree widget
QTreeWidgetItem *treeItem = new QTreeWidgetItem(ui->treeWidget);
treeItem->setText(0, "Pepedfsdf");
treeItem->setText(1, "Descdfsdfsdf");

The real question is if I can insert, in any time, elements into QTreeWidget and display it, because it seems that I can't. Maybe I have to call a special function to update the tree or anything, i don't know...