Inverted QTextEdit

Hi all,

I've taken an example from Qt labs (http://labs.trolltech.com/blogs/2009...e-in-qwebview/), trying to apply this to a QTextEdit.

Ultimately, this should give me a QTextEdit with all colors reversed, which I find easier on the eyes :)

Anyway, problem with this code is that after changing the setting (press F3), it should repaint the entire widget, but I can not get it to do so. I've tried both update() and repaint().

Any help would be appreciated!

Code:

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** Contact: Qt Software Information (qt-info@nokia.com)
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** This file is part of the Graphics Dojo project on Qt Labs.
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****************************************************************************/
 
#include <QtCore>
#include <QtGui>
 
#if QT_VERSION < 0x0040500
#error You need Qt 4.5 or newer
#endif
 
class NightModeView : public QTextEdit
{
    Q_OBJECT
 
public:
 
    NightModeView(QWidget *parent = 0): QTextEdit(parent), invert(true) {
        connect(this, SIGNAL(titleChanged(const QString&)), SLOT(setWindowTitle(const QString&)));
    }
 
private:
 
    bool invert;
 
    void paintEvent(QPaintEvent *event) {
        QTextEdit::paintEvent(event);
        if (invert) {
            QPainter p(viewport());
            p.setCompositionMode(QPainter::CompositionMode_Difference);
            p.fillRect(rect(), Qt::white);
            p.end();
        }
    }
 
    void keyPressEvent(QKeyEvent *event) {
        if (event->key() == Qt::Key_F3) {
            invert = !invert;
            update();
            event->accept();
            return;
        }
        QTextEdit::keyPressEvent(event);
    }
 
};
 
#include "webnightmode.moc"
 
int main(int argc, char **argv)
{
#ifdef Q_WS_X11
    QApplication::setGraphicsSystem("raster");
#endif
 
    QApplication app(argc, argv);
 
    NightModeView w;
    w.show();
 
    QMessageBox::information(&w, "Hint", "Use F3 to toggle night mode");
 
    return app.exec();
}

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If its any help, if I replace the

Code:

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update();

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in the code above with

Code:

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hide ();
show ();

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it does repaint the entire widget! However, that's obviously a dirty hack and not what I want.

QTextEdit is a QAbstractScrollArea. A ScrollArea delegates the painting of the content to its viewport. So use:

Code:

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viewport()->update();

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