Textedit - can't reset charFormat after highlight

[FabioG]

I'm trying to implement a shared text editor using c++ and qt. I would like to highlight the text inserted from different users with different colors. I can do that but the problem is that than I can't reset the charFormat and all the subsequent text I wrote is hihghlighted

Code I use to highlight and change charFormat

QTextCharFormat fmt;
fmt.setBackground(Qt::yellow);
insertCursor.setPosition(std::stoi(pos));
insertCursor.insertText(character.c_str(), fmt);
fmt.setBackground(Qt::white);
insertCursor.setCharFormat(fmt);

QTextCharFormat fmt;
fmt.setBackground(Qt::yellow);
insertCursor.setPosition(std::stoi(pos));
insertCursor.insertText(character.c_str(), fmt);
fmt.setBackground(Qt::white);
insertCursor.setCharFormat(fmt);

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some images to explain better
same file opened in 2 clients
Annotazione 2020-06-17 133258.jpg
left client wrote and right client updated text with highlight
Annotazione 2020-06-17 133259.jpg
right client wrote but remain highlighted
Annotazione 2020-06-17 133260.jpg

I also tried to use 2 different cursors one with the previous charFormat and one with one highlight settings and

moving the cursor locking the anchor this way

QTextCharFormat fmt;
    fmt.setBackground(Qt::yellow);
 
    QTextCursor cursor(ui->textEdit->document());
    cursor.setPosition(begin, QTextCursor::MoveAnchor);
    cursor.setPosition(end, QTextCursor::KeepAnchor);
    cursor.setCharFormat(fmt);
    fmt.setBackground(Qt::white);
    cursor.setCharFormat(fmt);

QTextCharFormat fmt;
    fmt.setBackground(Qt::yellow);

    QTextCursor cursor(ui->textEdit->document());
    cursor.setPosition(begin, QTextCursor::MoveAnchor);
    cursor.setPosition(end, QTextCursor::KeepAnchor);
    cursor.setCharFormat(fmt);
    fmt.setBackground(Qt::white);
    cursor.setCharFormat(fmt);

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(this is a function so I pass end and begin as values)

I suppose the problem could be related to the anchor that doesn't follow anymore the cursor or the fact the cursor use the previous character charFormat when I type but I really can't find out how to solve this problem

thanks to everyone in advice

[FabioG]

There's anyone that can help me?

I can add a video to explain better the problem and maybe reword the question





How can I change properly the charFormat of my text edit runtime?
And which is the best way to highlight a text?

also I modified the code a bit

Insert function:

QTextCharFormat fmt;
insertCursor.setPosition(std::stoi(pos));
ui->textEdit->setTextCursor(insertCursor);
ui->textEdit->insertPlainText(character.c_str());
HighlightText(user, std::stoi(pos), std::stoi(pos) + 1);
 
fmt.setBackground(Qt::white);
insertCursor.setCharFormat(fmt);
insertCursor.setPosition(std::stoi(pos) + 1, QTextCursor::MoveAnchor);

QTextCharFormat fmt;
insertCursor.setPosition(std::stoi(pos));
ui->textEdit->setTextCursor(insertCursor);
ui->textEdit->insertPlainText(character.c_str());
HighlightText(user, std::stoi(pos), std::stoi(pos) + 1);

fmt.setBackground(Qt::white);
insertCursor.setCharFormat(fmt);
insertCursor.setPosition(std::stoi(pos) + 1, QTextCursor::MoveAnchor);

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HighlightText function

void MainWindow::HighlightText(std::string user, int begin, int end){
    QTextCharFormat fmt;
    fmt.setBackground(Qt::yellow);
 
    QTextCursor cursor(ui->textEdit->document());
    cursor.setPosition(begin, QTextCursor::MoveAnchor);
    cursor.setPosition(end, QTextCursor::KeepAnchor);
    cursor.setCharFormat(fmt);
 
}

void MainWindow::HighlightText(std::string user, int begin, int end){
    QTextCharFormat fmt;
    fmt.setBackground(Qt::yellow);

    QTextCursor cursor(ui->textEdit->document());
    cursor.setPosition(begin, QTextCursor::MoveAnchor);
    cursor.setPosition(end, QTextCursor::KeepAnchor);
    cursor.setCharFormat(fmt);

}

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[ChrisW67]

I generated a basic QMainWindow project with aQTextEdit as the central widget. This code caches the formats and generates a stream of foreign text that switches from plain to highlighted and back without issue. run it an type continously for a few seconds. Useful?

#include "mainwindow.h"
#include "ui_mainwindow.h"
 
#include <QTimer>
 
MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
    , m_timer(nullptr)
{
    ui->setupUi(this);
 
    m_base = ui->textEdit->textCursor().charFormat();
    m_highlighted = m_base;
    m_highlighted.setBackground(Qt::yellow);
 
    m_timer = new QTimer(this);
    connect(m_timer, &QTimer::timeout, this, &MainWindow::writeForeignText);
    m_timer->setInterval(5000);
    m_timer->start();
}
 
MainWindow::~MainWindow()
{
    delete ui;
}
 
void MainWindow::writeForeignText()
{
    QTextCursor cursor = ui->textEdit->textCursor();
    cursor.setCharFormat(m_highlighted);
    cursor.insertText("Plugh");
    cursor.setCharFormat(m_base);
    ui->textEdit->setTextCursor(cursor);
}

#include "mainwindow.h"
#include "ui_mainwindow.h"

#include <QTimer>

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
    , m_timer(nullptr)
{
    ui->setupUi(this);

    m_base = ui->textEdit->textCursor().charFormat();
    m_highlighted = m_base;
    m_highlighted.setBackground(Qt::yellow);

    m_timer = new QTimer(this);
    connect(m_timer, &QTimer::timeout, this, &MainWindow::writeForeignText);
    m_timer->setInterval(5000);
    m_timer->start();
}

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

void MainWindow::writeForeignText()
{
    QTextCursor cursor = ui->textEdit->textCursor();
    cursor.setCharFormat(m_highlighted);
    cursor.insertText("Plugh");
    cursor.setCharFormat(m_base);
    ui->textEdit->setTextCursor(cursor);
}

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