Redirecting all cout statements to textEdit box

sf001

I'm very new to C++. I've been trying to correctly re-direct all of my cout statements in my program to instead print in a textEdit box in my mainWindow.cpp. Essentially, it would send everything that would have been displayed in the console to this box instead. My issue is that only cout statements that I write in mainwindow.cpp are being redirected to the text box. No cout statements from my main.cpp function is being sent there. The problem is probably stupid but I can't find it, and don't have a huge knowledge of C++. I do, however, need it to be done in this way.

mainwindow.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QWidget>
#include "main.h"
using namespace std;

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    redirect = new QDebugStream(std::cout, ui->textEdit);
    cout << "test" << endl;
}

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


void MainWindow::on_pushButton_clicked()
{

}

mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QWidget>
#include <QApplication>
#include <iostream>
#include <streambuf>
#include <string>
#include "qtextedit.h"


QT_BEGIN_NAMESPACE
namespace Ui {
    class MainWindow;
}
QT_END_NAMESPACE


class QDebugStream : public std::basic_streambuf<char>
{
public:
    QDebugStream(std::ostream &stream, QTextEdit *text_edit) : m_stream(stream)
    {
        log_window = text_edit;
        m_old_buf = stream.rdbuf();
        stream.rdbuf(this);
    }
    ~QDebugStream()
    {
// output anything that is left
        if (!m_string.empty())
            log_window->append(m_string.c_str());

        m_stream.rdbuf(m_old_buf);
    }

protected:
    virtual int_type overflow(int_type v)
    {
        if (v == '\n') {
            log_window->append(m_string.c_str());
            m_string.erase(m_string.begin(), m_string.end());
        } else
            m_string += v;

        return v;
    }

    virtual std::streamsize xsputn(const char *p, std::streamsize n)
    {
        m_string.append(p, p + n);

        int pos = 0;
        while (pos != std::string::npos) {
            pos = m_string.find('\n');
            if (pos != std::string::npos) {
                std::string tmp(m_string.begin(), m_string.begin() + pos);
                log_window->append(tmp.c_str());
                m_string.erase(m_string.begin(), m_string.begin() + pos + 1);
            }
        }

        return n;
    }

private:
    std::ostream &m_stream;
    std::streambuf *m_old_buf;
    std::string m_string;


    QTextEdit *log_window;
};




class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();


private slots:
    void on_pushButton_clicked();

private:
    Ui::MainWindow *ui;
    QDebugStream *redirect;
};

#endif // MAINWINDOW_H

I pulled the rdbuf code in mainwindow.h from online, as it seemed to meet my needs. I tried putting the stream buffer redirection code into the main.h file instead, and it didn't work. What am I missing?

jeremy_k

@sf001 said in Redirecting all cout statements to textEdit box:

I'm very new to C++. I've been trying to correctly re-direct all of my cout statements in my program to instead print in a textEdit box in my mainWindow.cpp. Essentially, it would send everything that would have been displayed in the console to this box instead. My issue is that only cout statements that I write in mainwindow.cpp are being redirected to the text box. No cout statements from my main.cpp function is being sent there.

What does main.cpp look like?

mainwindow.h


protected:
    virtual int_type overflow(int_type v)
    {
        if (v == '\n') {
            log_window->append(m_string.c_str());

virtual std::streamsize xsputn(const char *p, std::streamsize n)
{

[...]

            log_window->append(tmp.c_str());

This redirection isn't safe outside of the GUI thread.

nagesh

@sf001 said in Redirecting all cout statements to textEdit box:

No cout statements from my main.cpp function is being sent there.

redirect = new QDebugStream(std::cout, ui->textEdit);

redirect object is created in mainwindow. which is using ui->textEdit from mainwindow.
What have you done in main?
Do you have any cout messages in main after the mainwindow object creation?

Kent-Dorfman

https://stackoverflow.com/questions/18086193/redirect-stdout-stderr-to-file-under-unix-c-again