[Interest] Modify QCompleter's appearance

[Sensei]

I can reply to my own question.

First of all, I created a new QListWidget and connected it to the 
QCompleter, setting a layout and padding:


     list_ = new QListWidget(this);
     layout_ = new QVBoxLayout(list_);
     list_->setLayout(layout_);
     list_->setStyleSheet("QListWidget { padding: 15px 5px 5px 5px; 
border: 1px solid lightgray; }");

Next, make sure the completer works and knows about the widget:

     // Start the completer
     completer_ = new QCompleter();
     model_     = new QStringListModel();
     model_->setStringList(keywords_);
     completer_->setPopup(list_);
     completer_->setModel(model_);
     completer_->setWidget(this);
     completer_->setCaseSensitivity(Qt::CaseSensitive);

Ok. We're cool. Now in the keyPressEvent function you can set the mask 
for your custom appearance when showing the popup:


     // Show it!
     completer_->complete(cr);
     list_->resize(width_, height_);
     list_->setMask(mask);
     list_->hide();
     list_->show();


You can see that I hide and show the widget because I think I've hit a bug.

If you set a mask, and even when calling repaint(), the *widget frame* 
is visible, in other words, you see your correctly masked widget along 
with the original rectangular frame.

Hiding and reshowing it makes this visual annoyance go away. Repainting 
has not effect.