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

lukutis222

@JonB @dan1973
Thank you both very much. I am getting very close to where I want with my program.

Since autoscroll always automatically scrolls to cursor position, I no longer need

            QScrollBar *bar = ui->Console_read->verticalScrollBar();
            bar->setValue(bar->maximum());

My current function:

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

    while(serial_local->is_data_available()){
        if(ui->autoscroll->isChecked()){
            QTextCursor cursor = ui->Console_read->textCursor();
            cursor.clearSelection();
            cursor.movePosition(QTextCursor::End);
            ui->Console_read->setTextCursor(cursor);
        }
        else{
            //check if current cursor position is in the middle if so, set it to end of textedit else  show scrollbar to current position (not end of textedit or maximum)
            int  column_number = ui->Console_read->textCursor().columnNumber();
            qDebug("column number = %u \n",column_number);
            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);
                refresh_scrollbar = 1;
            }
            else{

            }
        }

        QByteArray line = serial_local->read_data();
        QString DataAsString = QString(line);
        logging_local->Write_to_file(DataAsString);

        //CAPTURE INFO LOGS
        if(DataAsString.contains(info_match)){
            DataAsString.replace(QRegularExpression("\\033\\1330;32m"), "");
            DataAsString.replace(QRegularExpression("\\033\\1330m"), "");
            ui->Console_read->setTextColor(QColor(0,128,0)); // 'custom' color
            ui->Console_read->insertPlainText(DataAsString);

        }
         //CAPTURE WARNING LOGS
        else if(DataAsString.contains(warning_match)){
            DataAsString.replace(QRegularExpression("\\033\\1330;33m"), "");
            DataAsString.replace(QRegularExpression("\\033\\1330m"), "");
            ui->Console_read->setTextColor(QColor(255,165,0)); // 'custom' color
            ui->Console_read->insertPlainText(DataAsString);


        }
        //CAPTURE ERROR LOGS
        else if(DataAsString.contains(error_match)){
            DataAsString.replace(QRegularExpression("\\033\\1330;31m"), "");
            DataAsString.replace(QRegularExpression("\\033\\1330m"), "");
            ui->Console_read->setTextColor(QColor(255,0,0)); // 'custom' color
            ui->Console_read->insertPlainText(DataAsString);

        }
        //All other data with ANSI code is printed in black color
        else{
            DataAsString.replace(QRegularExpression("\\033\\1330m"), "");
            ui->Console_read->setTextColor(Qt::black); //by default the text will be black
            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);
            refresh_scrollbar =  0;
        }

    }

}

I have a flag refresh_scrollbar which tells me when I need to restore the cursor position. Whenever I place cursor somewhere else apart from the end, my program gets stuck in this loop:

            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);
                refresh_scrollbar = 1;
            }

It will move the cursor to the end temporarily, write all the logs at the end of the file and then it will reposition the cursor back to where the cursor was moved:

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

The only issue now is when I click somewhere in the middle,:

1 second later (after the next block of messages is received from serial device) the cursor shifts up :

and it will remain there forever because my cursor position is not at the end hence my program is stuck in the loop setting the cursor at the end, writing logs and then moving the cursor back to the position where the mouse was clicked. I am not sure whether that is supposed to be correct behaviour. Is it possible for the cursor not to shift up and remain in exact same position even though the new messages keep coming?

Due to this issue, it becomes very difficult if I want to lets say copy some logs and paste it in separate notepad. As soon as I position my cursor in the middle, it shifts all the logs up and does not allow me to highlight text that I want to copy

dan1973

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

readData()

"The only issue now is when I click somewhere in the middle,:

1 second later (after the next block of messages is received from serial device) the cursor shifts up :"
this happens bcz the appended data is pushing the cursor up and you also need to apply setCursor position again after append.

"and it will remain there forever because my cursor position is not at the end hence my program is stuck in the loop setting the cursor at the end, writing logs and then moving the cursor back to the position where the mouse was clicked." ........obviously bcz you remembered the cursor pos of the mouse click and set to that pos.

"Is it possible for the cursor not to shift up and remain in exact same position even though the new messages keep coming?"......Yes. set CursorPos after append.

check yourself, are you using readyRead() signal of QT Serial or you are synchronously using timer reading the serial data?
Also, what is the data rate you get serial info?
Write_to_file() might be taking more time....always write to file when not reading from Serial or no data available in serial, you can open file...write to it and close it.. in a span of us or ms. keep writing to file in a background thread having a buffer which keeps appending the received line(QByteArray) data.
dont combine readying and writing operations here, keep them separate.
Also remember cursor postion using clicked event of QTextEdit.

checkoutfirst

This post is deleted!

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.