How to reposition cursor to the end of the document without autoscroll

[lukutis222]

@dan1973

I am using ready readRead signal to receive the data. There is no problems with reading the data. I read data every 1 second simply because the device that I am connected to prints every 1 second.

You mentioned:
this happens bcz the appended data is pushing the cursor up and you also need to apply setCursor position again after append.

But that is exactly what I am doing here isnt?

        if(refresh_scrollbar == 1){
            qDebug("refresh cursor to the old position \n");
            ui->Console_read->setTextCursor(cursor_backup);
            refresh_scrollbar = 0;
        }

After the data is appended, I check if refresh_scrollbar ==1 (it will be 1 if the cursor position is not at the bottom of the document), and then I set the cursor to the last saved position.

How can I then avoid my cursor to shift up when I placed my cursor in the middle and new data is received ?

Also, thank you for additional suggestions. I will try to implement them once I solve this issue.

So at the moment the logic is as following (when autoscroll is disabled):

Check if cursor is in the middle, if YES save the current cursor position using the function:
cursor_backup = ui->Console_read->textCursor();
After that, move the cursor to the end of the file to append the serial data, after appending serial data move back to the saved cursor position using the formula:
ui->Console_read->setTextCursor(cursor_backup);

[dan1973]

debug (i.e., qDebug()) on column_number after you ....

ui->Console_read->setTextCursor(cursor);

and after you append text

you need to know where is the cursor positioned after append. And also when you programmatically set the cursor to cursor_backup it should scroll to that position as well.

I suggest debug your code for two iterations, by keeping the data transfer rate to 10 sec. you will know the control flow here.

[lukutis222]

@dan1973 I have reflashed my remote device to send just 1 line of data every 1 second. It simply sending string: "HELLO FROM EXTERNAL DEVICE"

I simplified my ReadData function a little :

void Widget::readData()
{
    static bool refresh_scrollbar = 0;
    QTextCursor cursor_backup; // this is for saving cursor backup

    while(serial_local->is_data_available()){
        //if autoscroll is checked, just move the cursor to the end of the file which will automatically cause the autoscroll to happen
        if(ui->autoscroll->isChecked()){
            QTextCursor cursor = ui->Console_read->textCursor();
            cursor.clearSelection();
            cursor.movePosition(QTextCursor::End);
            ui->Console_read->setTextCursor(cursor);
        }
        else{

            int  column_number = ui->Console_read->textCursor().columnNumber();
            qDebug("column number initial = %u \n",column_number);
            // if cursor is in the middle, save the cursor backup, move the cursor to the end to append logs to the console and refresh the cursor to the "saved" position
            if(column_number != 0){
                cursor_backup = ui->Console_read->textCursor();
                QTextCursor cursor = ui->Console_read->textCursor();
                cursor.clearSelection();
                cursor.movePosition(QTextCursor::End);
                ui->Console_read->setTextCursor(cursor);
                int  column_number2 = ui->Console_read->textCursor().columnNumber();
                qDebug("column number after setTextCursor = %u \n",column_number2);
                refresh_scrollbar = 1;
            }
            else{

            }
        }

        QByteArray line = serial_local->read_data();
        QString DataAsString = QString(line);
        ui->Console_read->insertPlainText(DataAsString);


        //reposition the cursor once the write is complete
        if(refresh_scrollbar == 1){
            qDebug("refresh cursor to the old position \n");
            ui->Console_read->setTextCursor(cursor_backup);
            int  column_number3 = ui->Console_read->textCursor().columnNumber();
            qDebug("column number after append = %u \n",column_number3);
            refresh_scrollbar = 0;
        }

    }

}

If I click somewhere in the middle :

The autoscroll will and cursor will automatically adjust and put this line (where I placed my cursor initially) at the top of the QTextEdit window.

My program is then stuck in the loop adjusting the cursor position:

column number initial = 30 
column number after setTextCursor = 0 
refresh cursor to the old position 
column number after append = 30 
column number initial = 30 
column number after setTextCursor = 0 
refresh cursor to the old position 
column number after append = 30 
column number initial = 30 
column number after setTextCursor = 0 
refresh cursor to the old position 
column number after append = 30 
column number initial = 30 
column number after setTextCursor = 0 
refresh cursor to the old position 
column number after append = 30 
column number initial = 30 
column number after setTextCursor = 0 
refresh cursor to the old position 
column number after append = 30 
column number initial = 30 
column number after setTextCursor = 0 
refresh cursor to the old position 
column number after append = 30 

I am not sure if my usage of function:

int  column_number = ui->Console_read->textCursor().columnNumber();

is correct here

[dan1973]

 int  column_number = ui->Console_read->textCursor().columnNumber(); // Get Col No (30)
            qDebug("column number initial = %u \n",column_number);
            // if cursor is in the middle, save the cursor backup, move the cursor to the end to append logs to the console and refresh the cursor to the "saved" position
            if(column_number != 0){ 
                cursor_backup = ui->Console_read->textCursor(); // Get Cursor
                QTextCursor cursor = ui->Console_read->textCursor(); // Get Cursor
                cursor.clearSelection();
                cursor.movePosition(QTextCursor::End); // Move to End
                ui->Console_read->setTextCursor(cursor); // set Cursor to End
                int  column_number2 = ui->Console_read->textCursor().columnNumber(); // Get Col No (End pos)(0)
                qDebug("column number after setTextCursor = %u \n",column_number2);
                refresh_scrollbar = 1;
---
ui->Console_read->insertPlainText(DataAsString); // Insert Text at End
---
//reposition the cursor once the write is complete
        if(refresh_scrollbar == 1){
            qDebug("refresh cursor to the old position \n");
            ui->Console_read->setTextCursor(cursor_backup); // Position the cursor now to saved pos (30)
            int  column_number3 = ui->Console_read->textCursor().columnNumber(); // Get Col no
            qDebug("column number after append = %u \n",column_number3);
            refresh_scrollbar = 0;
        }

your cursor is working properly. it is moved to end (0) .... appends data......and then is moved back to saved pos (30).
Now check with mouse click event inside the QTextEdit and log and see.

[lukutis222]

@dan1973 Normally, I create all slots via the designer.

QTextEdit does not have mouse click event;

[jsulm]

@lukutis222 said in How to reposition cursor to the end of the document without autoscroll:

QTextEdit does not have mouse click event;

There is https://doc.qt.io/qt-6/qwidget.html#mousePressEvent

[lukutis222]

@jsulm I have read about the mouseclickevent and tried the following:

In my widget.h:

class Widget : public QWidget
{
    Q_OBJECT

public:


    Serial* serial_local; // this will be "local" instance of the Serial object that will point to the global Serial object.
    Logging* logging_local;
    TestTool* testtool_local;

    Widget(Serial* serial_ptr,Logging* logging_ptr,TestTool* testtool_ptr, QWidget *parent = nullptr);
    ~Widget();


    void fillPortsParameters();


private slots:

    void on_Scan_button_clicked();
    void on_Serial_connect_button_clicked();
    void readData();
    void on_write_box_returnPressed();
    void on_Scenario_select_currentIndexChanged(int index);



private:
    Ui::Widget *ui;


    QString error_match;
    QString info_match;
    QString warning_match;




protected:

    void mousePressEvent(QMouseEvent * event);



};

I have added:

protected:

    void mousePressEvent(QMouseEvent * event);

And then In my widget.cpp I have added:

void Widget::mousePressEvent(QMouseEvent *event)
{
    qDebug() << "Pressed";
}

Now when I click somewhere on my application I get this message printed "Pressed", however, the mouseclickevent is only registered when I click on an empty space. For example if I click anywhere on the QTextEdit window, it wont register, if I click on button "scan devices" or "connect" it will also not register.

Do I need to register an event for each widget instead of just my main Widget class?

[dan1973]

you need to override the mousePressEvent for QTextEdit instead of Widget class.

[JonB]

@lukutis222
Indeed, because the mouse event goes to the lower-level widget you click on.

Look at installing an application event filter, or on your Widget, for a convenient way of intercepting all mouse events, regardless of targeted widget: https://doc.qt.io/qt-6/eventsandfilters.html, https://doc.qt.io/qt-6/qobject.html#eventFilter. Otherwsie you will have to subclass and override mousePressEvent for every one of your widgets.

[lukutis222]

@dan1973
Yes I figured that but its not fully clear how to do it since I do not have a seperate class for QTextEdit. Can I do that in my Widget component?

Im not sure how to override QTextEdit mousePressEvent in some component (such as widget.h and widget.cpp) which does not have anything to do with QTextEdit

[dan1973]

.h file

protected:
void mouseMoveEvent(QMouseEvent *event) override;

.cpp file

void <yourWidgetClass>::mousePressEvent(QMouseEvent *e) {
    <handle event here>
}

[dan1973]

Sample appln
.h file

#ifndef WIDGET_H
#define WIDGET_H

#include <QWidget>
#include <QLabel>

QT_BEGIN_NAMESPACE
namespace Ui { class Widget; }
QT_END_NAMESPACE

class Widget : public QWidget
{
    Q_OBJECT

public:
    Widget(QWidget *parent = nullptr);
    ~Widget();
    bool bMPress;

protected:
    void mousePressEvent(QMouseEvent *event) override;
    void mouseReleaseEvent(QMouseEvent *event) override;
    void mouseMoveEvent(QMouseEvent *event) override;

private:
    Ui::Widget *ui;

    QLabel *lbl1;
};
#endif // WIDGET_H

.cpp file

#include "widget.h"
#include "ui_widget.h"
#include <QDebug>
#include <QCursor>

Widget::Widget(QWidget *parent) : QWidget(parent), ui(new Ui::Widget) {
    ui->setupUi(this);

    lbl1 = new QLabel("new", this);
    lbl1->setGeometry(20, 20, 100, 30);

    bMPress = false;

    setMouseTracking(true);
}

Widget::~Widget()
{
    delete ui;
}

void Widget::mousePressEvent(QMouseEvent *e) {
    bMPress = true;
    QString str1 = "\n X: " + QString::number(QCursor::pos().x()) + " Y: " + QString::number(QCursor::pos().x());
    qDebug() << str1;
}

void Widget::mouseMoveEvent(QMouseEvent *e) {
    if(bMPress) {
        QString str1 = "\n X: " + QString::number(QCursor::pos().x()) + " Y: " + QString::number(QCursor::pos().x());
        lbl1->setText(str1);
        this->repaint();
    }
}

void Widget::mouseReleaseEvent(QMouseEvent *e) {
    bMPress = false;
}

[lukutis222]

@dan1973

In my widget.h file I have now declared 2 mouse click events ( one for the Widget and the other one for the QTextEdit

In my header file, there is an error because It does not allow me to use override unless the function is virtual. When I add virtual to my function declaration in cpp:

There is another error regarding the virtual function declared outside class

[lukutis222]

@dan1973 In your example above you override Widget class function. I need to override QTextEdit mouseclick event

[jsulm]

@lukutis222 What you are doing does not make sence. If you want to override mousePressEvent in QTextEdit you need to subclass QTextEdit and do it there. Just like you did with QWidget. And then you use your subclass instead of QTextEdit.

[lukutis222]

@jsulm Yes I understand that but I was wondering if I need to create a seperate class just for QTextEdit so I can override one function? Can I make widget class inherit from QTextEdit and then override it in my widget class if that makes sense?

[jsulm]

@lukutis222 said in How to reposition cursor to the end of the document without autoscroll:

I was wondering if I need to create a seperate class just for QTextEdit so I can override one function?

Yes, this is how subclassing and overriding works.

"Can I make widget class inherit from QTextEdit and then override it in my widget class if that makes sense?" - not sure what you mean. As I sais: subclass QTextEdit and override in your subclass...

And please also read what @JonB suggested.

[JonB]

@lukutis222

@JonB said in How to reposition cursor to the end of the document without autoscroll:

Look at installing an application event filter, or on your Widget, for a convenient way of intercepting all mouse events, regardless of targeted widget: https://doc.qt.io/qt-6/eventsandfilters.html, https://doc.qt.io/qt-6/qobject.html#eventFilter. Otherwsie you will have to subclass and override mousePressEvent for every one of your widgets.

Should be pretty clear. Or you can ignore it.

[lukutis222]

@jsulm @JonB
JonB I do not ignore and I will definately look into this (eventfilters). I just want to learn first how to correctly override subclass methods because this is very interesting topic for me and very useful to learn. I am still learning C++ and I feel like this is very important to understand (which I struggle to do yet)

Just for the sake of testing, I have created a class with a QTextEdit base class:

custom_text_edit.cpp

#include "custom_text_edit.h"

custom_text_Edit::custom_text_Edit()
{

}

void custom_text_Edit::mousePressEvent(QMouseEvent *event)
{
    qDebug("pressed inside qtextedit \n");
}

custom_text_edit.h

#ifndef CUSTOM_TEXT_EDIT_H
#define CUSTOM_TEXT_EDIT_H

#include <QTextEdit>

class custom_text_Edit : public QTextEdit
{
public:
    custom_text_Edit();

protected:
    void mousePressEvent(QMouseEvent *event) override;
};

#endif // CUSTOM_TEXT_EDIT_H

I create class instance in my main.cpp:

custom_text_Edit cte;

Is there anything else I am missing? When I click on the QTextEdit widget ( my console), I still cannot trigger the mouseclick event that I just overriden

[jsulm]

@lukutis222 said in How to reposition cursor to the end of the document without autoscroll:

Is there anything else I am missing?

Yes, you are still using QTextEdit in your UI. You need to replace it with your custom_text_Edit.