Question

I want to add some syntax highlighting to text being written in QLineEdit, but it does not support rich text formatting, I can not change QlineEdit to something else, so I should find how to set color of text in this widget.

Is there a way to do this?

Answer 1

Just found a neat trick for that.

static void setLineEditTextFormat(QLineEdit* lineEdit, const QList<QTextLayout::FormatRange>& formats)
{
    if(!lineEdit)
        return;

    QList<QInputMethodEvent::Attribute> attributes;
    foreach(const QTextLayout::FormatRange& fr, formats)
    {
        QInputMethodEvent::AttributeType type = QInputMethodEvent::TextFormat;
        int start = fr.start - lineEdit->cursorPosition();
        int length = fr.length;
        QVariant value = fr.format;
        attributes.append(QInputMethodEvent::Attribute(type, start, length, value));
    }
    QInputMethodEvent event(QString(), attributes);
    QCoreApplication::sendEvent(lineEdit, &event);
}

static void clearLineEditTextFormat(QLineEdit* lineEdit)
{
    setLineEditTextFormat(lineEdit, QList<QTextLayout::FormatRange>());
}

// Usage example:
QLineEdit* lineEdit = new QLineEdit;
lineEdit->setText(tr("Task Tracker - Entry"));

QList<QTextLayout::FormatRange> formats;

QTextCharFormat f;

f.setFontWeight(QFont::Bold);
QTextLayout::FormatRange fr_task;
fr_task.start = 0;
fr_task.length = 4;
fr_task.format = f;

f.setFontItalic(true);
f.setBackground(Qt::darkYellow);
f.setForeground(Qt::white);
QTextLayout::FormatRange fr_tracker;
fr_tracker.start = 5;
fr_tracker.length = 7;
fr_tracker.format = f;

formats.append(fr_task);
formats.append(fr_tracker);

setLineEditTextFormat(lineEdit, formats);