[Qt-interest] Faster logfile viewer

[Thomas Dähling]

Try using a QPlainTextEdit instead of a QTextEdit. Not sure how much
performance improvement it will bring (no Qt installed on this machine
so cannot test it) but it is supposed to be a lot faster since it's
position calculations are a lot simpler than those in QTextEdit.

Am 4. August 2009 17:24 schrieb Christoph Bartoschek <bartoschek at gmx.de>:
> Hi,
>
> consider the program at the end of the post. It shows a TextEdit and a
> PushButton. When you press the button 10000 lines are appended to the
> TextEdit and the view is updated. The whole procedure takes 47 Seconds on
> my machine.
>
> Our old Motif application does the same within less then a second. How can I
> get a performace that is comparable to our old application with Qt?
>
> Thanks,
> Christoph
>
> main.cpp:
>
> #include <QApplication>
> #include "ama.hpp"
>
> int main(int argc, char ** argv) {
>   QApplication app(argc, argv);
>   Ama edit;
>   edit.show();
>   app.exec();
> }
>
> ama.hpp:
>
> #include <QtGui>
> #include <iostream>
>
> class Ama : public QTextEdit {
> Q_OBJECT
> public:
>     Ama();
> public slots:
>      void start();
> private:
>     QPushButton but;
> };
>
> ama.cpp:
>
> #include <iostream>
> #include "ama.hpp"
>
> Ama::Ama() : QTextEdit() {
>   but.show();
>   connect(&but, SIGNAL(clicked()), this, SLOT(start()));
> }
>
> void Ama::start() {
>   QTime time;
>   time.start();
>   for (int i = 0; i < 10000; ++i) {
>      QString str = QString("I ist %1").arg(i);
>      this->append(str);
>      repaint();
>   }
>   std::cout << "Elapsed " << time.elapsed()  / 1000.0<< std::endl;
> }
>
>
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