Qt FramelessWindowHint and WA_TranslucentBackground Font Rendering - c++

Question

I am writing an application with a custom window shell. The shell has rounded corners and transparency. Here is the sample code of how I am doing this:
MyWindow::MyWindow (void) : QMainWindow (NULL, Qt::FramelessWindowHint)
{
setAttribute (Qt::WA_TranslucentBackground);
setAttribute (Qt::WA_NoSystemBackground );
}
The problem is whenever I use WA_TranslucentBackground with FramelessWindowHint, the font rendering becomes awful, see image below. I have a custom application style set through a global css. I tried using other fonts such as Segoe UI however that font also becomes changed.
Any ideas on why this is happening and what I can do to fix this problem. I am using C++ with Qt 5.0.2

Answer 1

It looks like I may have found a solution. First of all, you can use QWidget::setMask in order to get rounded corners if you prefer to not use Qt::WA_TranslucentBackground. Here is the sample code I came up with:
void MyWindow::setVisible (bool visible)
{
// Call the default event
QMainWindow::setVisible (visible);
// Set a rounded mask (size() needs to be correct)
QBitmap t (size());
t.fill (Qt::color0);
QPainter p (&t);
p.setBrush (Qt::color1);
p.drawRoundedRect (rect(), 5, 5);
setMask (t);
}
For transparency you have to make the font prefer antialiasing. You can put this at the start of the application.
QFont font = QApplication::font();
font.setStyleStrategy (QFont::PreferAntialias);
QApplication::setFont (font);
Not perfect but it fixed the problem I was having.