qt - QTextEdit and colored bash-like output emulation

Question

I have an escape sequences in a text, like

char const * text = "e[1;33m" "some colored text" "e[0m";

Which usually printed in terminal. But I want to forward this text in QTextEdit.

What is the simpliest way to make such text in QTextEdit colored? How to perform a filtering of escape sequences, i.e. how replace its with proper text formatting?

I think there is QSyntaxHighlighter-aided solution possible, but I don't know what to do with escape sequences itself and how to hide they from the output.

Answer 1

Finally, I found the approach (it is understood, that QTextEdit::setReadOnly(true)):

// based on information: http://en.m.wikipedia.org/wiki/ANSI_escape_code http://misc.flogisoft.com/bash/tip_colors_and_formatting http://invisible-island.net/xterm/ctlseqs/ctlseqs.html
void MainWindow::parseEscapeSequence(int attribute, QListIterator< QString > & i, QTextCharFormat & textCharFormat, QTextCharFormat const & defaultTextCharFormat)
{
    switch (attribute) {
    case 0 : { // Normal/Default (reset all attributes)
        textCharFormat = defaultTextCharFormat;
        break;
    }
    case 1 : { // Bold/Bright (bold or increased intensity)
        textCharFormat.setFontWeight(QFont::Bold);
        break;
    }
    case 2 : { // Dim/Faint (decreased intensity)
        textCharFormat.setFontWeight(QFont::Light);
        break;
    }
    case 3 : { // Italicized (italic on)
        textCharFormat.setFontItalic(true);
        break;
    }
    case 4 : { // Underscore (single underlined)
        textCharFormat.setUnderlineStyle(QTextCharFormat::SingleUnderline);
        textCharFormat.setFontUnderline(true);
        break;
    }
    case 5 : { // Blink (slow, appears as Bold)
        textCharFormat.setFontWeight(QFont::Bold);
        break;
    }
    case 6 : { // Blink (rapid, appears as very Bold)
        textCharFormat.setFontWeight(QFont::Black);
        break;
    }
    case 7 : { // Reverse/Inverse (swap foreground and background)
        QBrush foregroundBrush = textCharFormat.foreground();
        textCharFormat.setForeground(textCharFormat.background());
        textCharFormat.setBackground(foregroundBrush);
        break;
    }
    case 8 : { // Concealed/Hidden/Invisible (usefull for passwords)
        textCharFormat.setForeground(textCharFormat.background());
        break;
    }
    case 9 : { // Crossed-out characters
        textCharFormat.setFontStrikeOut(true);
        break;
    }
    case 10 : { // Primary (default) font
        textCharFormat.setFont(defaultTextCharFormat.font());
        break;
    }
    case 11 ... 19 : {
        QFontDatabase fontDatabase;
        QString fontFamily = textCharFormat.fontFamily();
        QStringList fontStyles = fontDatabase.styles(fontFamily);
        int fontStyleIndex = attribute - 11;
        if (fontStyleIndex < fontStyles.length()) {
            textCharFormat.setFont(fontDatabase.font(fontFamily, fontStyles.at(fontStyleIndex), textCharFormat.font().pointSize()));
        }
        break;
    }
    case 20 : { // Fraktur (unsupported)
        break;
    }
    case 21 : { // Set Bold off
        textCharFormat.setFontWeight(QFont::Normal);
        break;
    }
    case 22 : { // Set Dim off
        textCharFormat.setFontWeight(QFont::Normal);
        break;
    }
    case 23 : { // Unset italic and unset fraktur
        textCharFormat.setFontItalic(false);
        break;
    }
    case 24 : { // Unset underlining
        textCharFormat.setUnderlineStyle(QTextCharFormat::NoUnderline);
        textCharFormat.setFontUnderline(false);
        break;
    }
    case 25 : { // Unset Blink/Bold
        textCharFormat.setFontWeight(QFont::Normal);
        break;
    }
    case 26 : { // Reserved
        break;
    }
    case 27 : { // Positive (non-inverted)
        QBrush backgroundBrush = textCharFormat.background();
        textCharFormat.setBackground(textCharFormat.foreground());
        textCharFormat.setForeground(backgroundBrush);
        break;
    }
    case 28 : {
        textCharFormat.setForeground(defaultTextCharFormat.foreground());
        textCharFormat.setBackground(defaultTextCharFormat.background());
        break;
    }
    case 29 : {
        textCharFormat.setUnderlineStyle(QTextCharFormat::NoUnderline);
        textCharFormat.setFontUnderline(false);
        break;
    }
    case 30 ... 37 : {
        int colorIndex = attribute - 30;
        QColor color;
        if (QFont::Normal < textCharFormat.fontWeight()) {
            switch (colorIndex) {
            case 0 : {
                color = Qt::darkGray;
                break;
            }
            case 1 : {
                color = Qt::red;
                break;
            }
            case 2 : {
                color = Qt::green;
                break;
            }
            case 3 : {
                color = Qt::yellow;
                break;
            }
            case 4 : {
                color = Qt::blue;
                break;
            }
            case 5 : {
                color = Qt::magenta;
                break;
            }
            case 6 : {
                color = Qt::cyan;
                break;
            }
            case 7 : {
                color = Qt::white;
                break;
            }
            default : {
                Q_ASSERT(false);
            }
            }
        } else {
            switch (colorIndex) {
            case 0 : {
                color = Qt::black;
                break;
            }
            case 1 : {
                color = Qt::darkRed;
                break;
            }
            case 2 : {
                color = Qt::darkGreen;
                break;
            }
            case 3 : {
                color = Qt::darkYellow;
                break;
            }
            case 4 : {
                color = Qt::darkBlue;
                break;
            }
            case 5 : {
                color = Qt::darkMagenta;
                break;
            }
            case 6 : {
                color = Qt::darkCyan;
                break;
            }
            case 7 : {
                color = Qt::lightGray;
                break;
            }
            default : {
                Q_ASSERT(false);
            }
            }
        }
        textCharFormat.setForeground(color);
        break;
    }
    case 38 : {
        if (i.hasNext()) {
            bool ok = false;
            int selector = i.next().toInt(&ok);
            Q_ASSERT(ok);
            QColor color;
            switch (selector) {
            case 2 : {
                if (!i.hasNext()) {
                    break;
                }
                int red = i.next().toInt(&ok);
                Q_ASSERT(ok);
                if (!i.hasNext()) {
                    break;
                }
                int green = i.next().toInt(&ok);
                Q_ASSERT(ok);
                if (!i.hasNext()) {
                    break;
                }
                int blue = i.next().toInt(&ok);
                Q_ASSERT(ok);
                color.setRgb(red, green, blue);
                break;
            }
            case 5 : {
                if (!i.hasNext()) {
                    break;
                }
                int index = i.next().toInt(&ok);
                Q_ASSERT(ok);
                switch (index) {
                case 0x00 ... 0x07 : { // 0x00-0x07:  standard colors (as in ESC [ 30..37 m)
                    return parseEscapeSequence(index - 0x00 + 30, i, textCharFormat, defaultTextCharFormat);
                }
                case 0x08 ... 0x0F : { // 0x08-0x0F:  high intensity colors (as in ESC [ 90..97 m)
                    return parseEscapeSequence(index - 0x08 + 90, i, textCharFormat, defaultTextCharFormat);
                }
                case 0x10 ... 0xE7 : { // 0x10-0xE7:  6*6*6=216 colors: 16 + 36*r + 6*g + b (0≤r,g,b≤5)
                    index -= 0x10;
                    int red = index % 6;
                    index /= 6;
                    int green = index % 6;
                    index /= 6;
                    int blue = index % 6;
                    index /= 6;
                    Q_ASSERT(index == 0);
                    color.setRgb(red, green, blue);
                    break;
                }
                case 0xE8 ... 0xFF : { // 0xE8-0xFF:  grayscale from black to white in 24 steps
                    qreal intensity = qreal(index - 0xE8) / (0xFF - 0xE8);
                    color.setRgbF(intensity, intensity, intensity);
                    break;
                }
                }
                textCharFormat.setForeground(color);
                break;
            }
            default : {
                break;
            }
            }
        }
        break;
    }
    case 39 : {
        textCharFormat.setForeground(defaultTextCharFormat.foreground());
        break;
    }
    case 40 ... 47 : {
        int colorIndex = attribute - 40;
        QColor color;
        switch (colorIndex) {
        case 0 : {
            color = Qt::darkGray;
            break;
        }
        case 1 : {
            color = Qt::red;
            break;
        }
        case 2 : {
            color = Qt::green;
            break;
        }
        case 3 : {
            color = Qt::yellow;
            break;
        }
        case 4 : {
            color = Qt::blue;
            break;
        }
        case 5 : {
            color = Qt::magenta;
            break;
        }
        case 6 : {
            color = Qt::cyan;
            break;
        }
        case 7 : {
            color = Qt::white;
            break;
        }
        default : {
            Q_ASSERT(false);
        }
        }
        textCharFormat.setBackground(color);
        break;
    }
    case 48 : {
        if (i.hasNext()) {
            bool ok = false;
            int selector = i.next().toInt(&ok);
            Q_ASSERT(ok);
            QColor color;
            switch (selector) {
            case 2 : {
                if (!i.hasNext()) {
                    break;
                }
                int red = i.next().toInt(&ok);
                Q_ASSERT(ok);
                if (!i.hasNext()) {
                    break;
                }
                int green = i.next().toInt(&ok);
                Q_ASSERT(ok);
                if (!i.hasNext()) {
                    break;
                }
                int blue = i.next().toInt(&ok);
                Q_ASSERT(ok);
                color.setRgb(red, green, blue);
                break;
            }
            case 5 : {
                if (!i.hasNext()) {
                    break;
                }
                int index = i.next().toInt(&ok);
                Q_ASSERT(ok);
                switch (index) {
                case 0x00 ... 0x07 : { // 0x00-0x07:  standard colors (as in ESC [ 40..47 m)
                    return parseEscapeSequence(index - 0x00 + 40, i, textCharFormat, defaultTextCharFormat);
                }
                case 0x08 ... 0x0F : { // 0x08-0x0F:  high intensity colors (as in ESC [ 100..107 m)
                    return parseEscapeSequence(index - 0x08 + 100, i, textCharFormat, defaultTextCharFormat);
                }
                case 0x10 ... 0xE7 : { // 0x10-0xE7:  6*6*6=216 colors: 16 + 36*r + 6*g + b (0≤r,g,b≤5)
                    index -= 0x10;
                    int red = index % 6;
                    index /= 6;
                    int green = index % 6;
                    index /= 6;
                    int blue = index % 6;
                    index /= 6;
                    Q_ASSERT(index == 0);
                    color.setRgb(red, green, blue);
                    break;
                }
                case 0xE8 ... 0xFF : { // 0xE8-0xFF:  grayscale from black to white in 24 steps
                    qreal intensity = qreal(index - 0xE8) / (0xFF - 0xE8);
                    color.setRgbF(intensity, intensity, intensity);
                    break;
                }
                }