Highlight text question

[SherifOmran]

hello guys,

I wrote a program to highlight a text as requested from the mainwindow but my problem is that the highlight appears only when text is changed and I want it to appear when a corrected character is added in mainwindow highlighter->addmistake(1); . here is my code

highlighter.h
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#ifndef HIGHLIGHTER_H
#define HIGHLIGHTER_H

#include <QSyntaxHighlighter>
#include <QHash>
#include <QTextCharFormat>

QT_BEGIN_NAMESPACE
class QTextDocument;
QT_END_NAMESPACE

//! [0]
class Highlighter : public QSyntaxHighlighter
{
Q_OBJECT

public:
Highlighter(QTextDocument *parent = 0);
void addmistake(int pos);
QList <int> corrections;

protected:
void highlightBlock(const QString &text);

private:

struct Mistakes
{
    int position;
};
QVector <Mistakes> mistakes;

void updatefn();

};
//! [0]

#endif

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highlighter.cpp

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#include <QtGui>
#include <QDebug>
#include "highlighter.h"

QString doctext;

Highlighter::Highlighter(QTextDocument *parent)
: QSyntaxHighlighter(parent)
{
}

void Highlighter::addmistake(int pos)
{
// call this function to add reference to a mistake character
corrections.append(pos);
qDebug() << "added " << pos;

}

void Highlighter::highlightBlock(const QString &text)
{
qDebug () << "correction size " << corrections.size();
updatefn();
qDebug() << text << "block";

}

void Highlighter::updatefn()
{
// this function updates the coloring
for (int i=0; i < corrections.size(); ++i)
{
setFormat(corrections.at(i),1,QColor(255,0,0));
}

setCurrentBlockState(0);

}

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mainwindow
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#include <QtGui>
#include "mainwindow.h"

MainWindow::MainWindow(QWidget *parent)
: QMainWindow(parent)
{

QFont font;
font.setFamily("Courier");
font.setFixedPitch(true);
font.setPointSize(30);

editor = new QTextEdit;
editor->setFont(font);

highlighter = new Highlighter(editor->document());

editor->setPlainText("Hello World");
setCentralWidget(editor);
highlighter->addmistake(1); // change color of 2nd character

}
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