Qt - Moving Frameless window (slow repaint?) - qt

Question

Hy there,
I'm new to Qt and i tried to create a Frameless window, which is dragable. The Problem is, if i move the window.. there are are thousands of (it? sorry, don't know how to describe it in english) until i stop.
Is there a way to fix this, or am i thinking the wrong way?
MyWindow.h
#include <QMainWindow>
#include <QLabel>
#include <QPushButton>
#include <QMouseEvent>
class MyWindow : public QMainWindow {
Q_OBJECT
private:
QLabel *label_title,*label_quit;
QPushButton *bn_exit;
QPixmap *pixmap;
QPoint m_dragPosition;
public:
MyWindow(QMainWindow *parent = 0, Qt::WindowFlags flags = 0);
protected:
void paintEvent(QPaintEvent *event);
void mouseMoveEvent(QMouseEvent *event);
void mousePressEvent(QMouseEvent *event);
};
MyWindow.cpp
#include "MyWindow.h"
#include <QApplication>
#include <QPainter>
#include <QLabel>
MyWindow::MyWindow(QMainWindow *parent, Qt::WindowFlags flags) : QMainWindow(parent,flags) {
resize(1024,576);
setWindowTitle("Versuch1");
//Titel
label_title = new QLabel("irgendwas",this);
label_title->setGeometry(10,10,500,40);
label_title->setStyleSheet("font-family: Arial; letter-spacing: 4px;font-weight:bold; color : white;font-size: 30px");
//Exit-Button
bn_exit = new QPushButton("[Exit]",this);
bn_exit->setGeometry(975,10,40,20);
bn_exit->setStyleSheet("QPushButton {font-family: Verdana; font-size:15px; top:0px; border: none; background-color:#101010; color:white} QPushButton:hover {color: red }");
connect(bn_exit,SIGNAL(clicked()),qApp,SLOT(quit()));
}
void MyWindow::paintEvent(QPaintEvent *event) // Painter
{
QPainter painter(this);
painter.setPen(Qt::NoPen); // deactivate Border
painter.setBrush(QBrush("#101010")); // black title and footer
painter.drawRect(0, 0, 1024, 60);
painter.setBrush(QBrush("#101010"));
painter.drawRect(0, 516, 1024, 576);
}
void MyWindow::mouseMoveEvent(QMouseEvent *event)
{
if (event->buttons() & Qt::LeftButton) {
move(event->globalPos() - m_dragPosition);
event->accept();
}
}
void MyWindow::mousePressEvent(QMouseEvent *event)
{
if (event->button() == Qt::LeftButton) {
m_dragPosition = event->globalPos() - frameGeometry().topLeft();
event->accept();
}
}
main.cpp
#include <QApplication>
#include "MyWindow.h"
int main(int argc, char *argv[]) {
QApplication app(argc, argv);
MyWindow* window = new MyWindow(0, Qt::FramelessWindowHint);
window->show();
return app.exec();
}
Greetings,
Alex

Answer 1

You might want to try calling the base class methods in your protected methods. For example:
void MyWindow::paintEvent(QPaintEvent *event) // Painter
{
QWidget::paintEvent(event);
...
}
void MyWindow::mouseMoveEvent(QMouseEvent *event)
{
QWidget::moveMouseEvent(event);
...
}

Answer 2

I could not reproduce your problem (Ubuntu or XP) but how about trying to process repaint events:
if (event->buttons() & Qt::LeftButton) {
move(event->globalPos() - m_dragPosition);
event->accept();
QCoreApplication::processEvents(QEventLoop::ExcludeUserInputEvents);
}
It might be that your system is running low on resources or your display driver is "slow". Try it with a clean reboot and only your app open.