[vtkusers] QWidget::paintEvent(..) Bug on Windows?

[Jens Henrik Goebbert]

Hi Trolltech

As Clinton Stimpson already wrote, there is a bug with QWidget::paintEvent(..) 
on Windows (not no X11) when impementing a paintEvent like this:
virtual void paintEvent(QPaintEvent*)
  {
    ::BeginPaint(this->winId(), &ps);
    HDC dc = GetDC(this->winId());
    ::SetRect(&box, 0,0, width(), height());
    ::FillRect(dc, &box, brush);
    ::EndPaint(this->winId(), &ps);
  }

Here what he wrote:
Below is a Windows app to demonstrate the problem.
If I step through the code with a debugger, the widget is correctly 
painted blue when EndPaint() is called.
But when I step out of the paintEvent function, Qt appears to erase the 
widget.  So I never see any blue on my widget except when I'm stepping 
through the code.

I've also seen similar problems when resizing where artifacts from 
toolbars show up after paintEvent is called for my custom widget -- 
although this example doesn't demonstrate that problem.

Bye
	Jens HEnrik

The demonstration app works fine in Qt3 and Qt4/X11, but doesn't work with 
Qt4/Windows.
=====================================
#include <qapplication.h>
#include <qmainwindow.h>
#include <qpainter.h>
#include <windows.h>

class MyCustomWidget : public QWidget
{

  HBRUSH brush;
  PAINTSTRUCT ps;
  RECT box;

public:
  MyCustomWidget(QWidget* parent) : QWidget(parent)
  {
    brush = ::CreateSolidBrush(0x00FF0000);  // blue
  };
  ~MyCustomWidget()
  {
    ::DeleteObject(brush);
  }

  virtual void paintEvent(QPaintEvent*)
  {
    ::BeginPaint(this->winId(), &ps);
    HDC dc = GetDC(this->winId());
    ::SetRect(&box, 0,0, width(), height());
    ::FillRect(dc, &box, brush);
    ::EndPaint(this->winId(), &ps);
  }
};

int main( int argc, char* argv[] )
{
    QApplication app(argc, argv);
    QMainWindow window;

    MyCustomWidget* widget = new MyCustomWidget( &window );
    window.setCentralWidget( widget );

    window.show();
    return app.exec();
}