QCombobox's popup list border radius skinning (drop list)

[timohan]

Hi,

I try skin QCombobox's border with custom pictures.
The problem comes that it seems QCombobox's list view popup have somekind background drawing on drop list.

For example:
I have own custom combobox, and I try set border radius via style sheet.
----------------
CComboBox::CComboBox(QWidget *parent) : QComboBox(parent)
{
QString strStyle = "QComboBox QAbstractItemView { background-image: none; background: transparent; border: 3px solid darkgray; selection-background-color: red; border-top-right-radius: 13px; border-bottom-right-radius: 13px; border-bottom-left-radius: 13px; border-top-left-radius: 13px; };";

setStyleSheet(strStyle);
}
------------
This doesn't actually work, because it still does draw something square behind it. and I am trying to understand what is that behind the list popup....

and how can I remove or change that popup's drawing behind the popup list view.

Here is the problem with that stylesheet in picture, so you can see the square in popup listbox behind radius:
http://www.timogames.com/test/combobox_popup.png

[gnuton]

Hi,
The "square" drawn behind the ComboBox list is a Dialog.
I guess that list needs the Qt::WA_TranslucentBackground attribute set with QWidget::setAttribute().

[timohan]

As I understand, it's QFrame that is WindowFlag WS:Popup.....

I have tried:
CComboBox::CComboBox(QWidget *parent) : QComboBox(parent)
{
view()->parentWidget()->setAttribute(Qt::WA_TranslucentBackground);
view()->parentWidget()->setWindowFlags(Qt::Popup | Qt::FramelessWindowHint);
}
But it does still draw a shadow.
------ I can set shadow off (but then it stops being popup and stops following the application & combobox)
CComboBox::CComboBox(QWidget *parent) : QComboBox(parent)
{
view()->parentWidget()->setAttribute(Qt::WA_TranslucentBackground);
view()->parentWidget()->setWindowFlags(Qt::Window | Qt::FramelessWindowHint);
}
(this is way, no shadow, but then it's wrong other way).
-----------
Also:
view()->parentWidget()->setWindowFlags(Qt::Popup | Qt::Window | Qt::FramelessWindowHint);
doesn't help....
-----------

[gnuton]

Well, it could be a QFrame or whatever. The important thing as you said is the WA.

view()->parentWidget()->setWindowFlags(Qt::Popup | Qt::Window | Qt::FramelessWindowHint); doesn't really help because Qt::Popup is already a Qt::Window.
IIRC if you look inside the Qt code (QtGUI Module) you will find out that Qt::Popup is basically Qt::Popup | Qt::Window.

The point here is that Windows attributes behave in different ways according to the window manager of your desktop system,
and you need just few of behaviour which are given to Qt::Popup on windows.

To forget about WM relates issue there is a simple way, but I don't know if can be valid for your case.
Basically you can embedd your widget inside a QGraphicsView through a QGraphicsViewProxy.
This way you don't need to set WAs and I believe your stylesheet should work correctly.

[timohan]

You mean, like this?
----
CComboBox::CComboBox(QWidget *parent) : QComboBox(parent)
{
QGraphicsScene *scene = new QGraphicsScene();
QGraphicsProxyWidget *proxy = scene->addWidget( view()->parentWidget() );
QGraphicsView *view1 = new QGraphicsView(scene);
}
---
This doesn't work at all. I am not very good using QGraphicsView.

if I use: view1->show();
it does create additional dialog, and drop list box appears on it, but it doesn't work at all as it should be.

[gnuton]

Hi,
the graphicsview is a QWidget. If you instantiate it with
QGraphicsView *view1 = new QGraphicsView(scene),

you basically create a new dialog since the graphicsview doesn't have any parent.

Having a new top level widget is actaully the thing you want to avoid; and this is something you can do using a GraphicsView.
You may create the GraphicsView as child of your MainWindow. In this case, the GraphicsView should be transparent and cover the entire app.
This about it as a simple transparent canvas where you can draw your widget.
Then you can draw the popup list inside the graphics view.

For sure this is an hack. The right and clean way to do what you are trying to so is to use these methods
setAttribute(Qt::WA_TranslucentBackground);
setWindowFlags(Qt::Window | Qt::FramelessWindowHint);

but you said they lead to some other problems, which you have not actually described.
Feel free to detail more about this issue or just ask more if get stuck with implementation of the graphics view way.

[timohan]

I have also tried:
QGraphicsView *view1 = new QGraphicsView(scene, view()->parentWidget()->parentWidget());
or:
QGraphicsView *view1 = new QGraphicsView(scene, view()->parentWidget());
But it doesn't help either. popup appears for second and then disappears somewhere.
-----------
I also noted another problem.
Making stylesheet border + radius corner, does mess up with scrollbars, and stylesheet's border (radius) doesn't appear if scrollbar is active on listbox's corner areas. it's ok only if listbox doesn't have scrollbar.
-----------
Could you give more code specific help. I have tried many ways, but I just cannot get shadow disappear correctly. Note that QFrame "dialog" should be WS:POPUP it and it does cause the shadow drawing, otherwise it doesn't sync with combobox.