TextEdit painting C++

LittleFire

Hi everyone,
I read many posts of how to paint on Qtextedit, but I cannot get out of the problem.

I create a form with a qtextedit named text and a class named textedit. Then, I wrote paintEvent(QPaintEvent* event) method in this way:

void textedit::paintEvent(QPaintEvent* event)
{
        QCursor cursorQ = ui->text->cursor();
        QPoint point= cursorQ.pos();
        QPainter p(this);
        p.drawText(QPoint(30,30), "|");
        p.drawText(point, "|");
}

The first drawText works and draw "|" character out of the QTextEdit area in the QPoint(30, 30), the second don't and I don't understand why.
It's produced:
"QWidget::paintEngine: Should no longer be called
QPainter::begin: Paint device returned engine == 0, type: 1"
output.
Maybe it is because QPainter is reffered to the entire window and QPoint only to Qtextedit area? If this is the reason, how can I get what I want?
I read some posts where people recommend using

QPainter p(viewport());

but it produced "used of undeclared identifier viewport " error.

What can I have miss?

(I used drawtext only as example for me, for understanding how to paint in the QTextEdit area)

There .cpp and .h files:

#ifndef TEXTEDIT_H
#define TEXTEDIT_H

#include <QMainWindow>
#include <QCursor>
#include <unistd.h>
#include <QTextCharFormat>
#include <QTextCursor>
#include <QDebug>
#include <QPainter>

namespace Ui {
class textedit;
}

class textedit : public QMainWindow
{
    Q_OBJECT

public:
    explicit textedit(QWidget *parent = nullptr);
    ~textedit();

private:
    Ui::textedit *ui;
    QTextCursor cursor;

protected:
    void paintEvent(QPaintEvent* event);
};

#endif // TEXTEDIT_H

#include "textedit.h"
#include "ui_textedit.h"

textedit::textedit(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::textedit)
{
    ui->setupUi(this);
    ui->text->setText("Hello, World!\nAnotherLine.\n");

}

textedit::~textedit()
{
    delete ui;
}
void textedit::paintEvent(QPaintEvent* event)
{
        QCursor cursorQ = ui->text->cursor();
        QPoint point= cursorQ.pos();
        QPainter p(this);
        p.drawText(QPoint(30,30), "|");
        p.drawText(point, "|");
}

Thanks for any reply or advice.

SGaist

Hi,

point is likely local to the QTextEdit so completely unrelated to your QMainWindow. You have to translate the coordinate to make it draw where you want.

LittleFire

@SGaist how can I do this? For what I need I have to start from the cursor position

SGaist

Take a look at the various point mapping related functions.

LittleFire

@SGaist Thank you!