Expose QComboBox to QML

[philk]

This code initially somewhat draws the combobox in my QML document. But it does not seem to react on clicks or keyboard events. The paint handler is called only once.

@
class CountryComboBoxQmlAdapter : public QQuickPaintedItem {
Q_OBJECT
public:
explicit CountryComboBoxQmlAdapter(QQuickItem* parent = nullptr);

void paint(QPainter * painter) override;
private:
QComboBox* m_combo;
QGraphicsProxyWidget* m_proxy;
};
@

@

CountryComboBoxQmlAdapter::CountryComboBoxQmlAdapter(QQuickItem* parent) : QQuickPaintedItem(parent) {
setFlag(ItemHasContents, true);
m_combo = new QComboBox;
m_combo->setEditable(true);
m_combo->setFrame(false);

CountriesListModel* model = new CountriesListModel(this);
m_combo->setModel(model);
m_proxy = new QGraphicsProxyWidget;
m_proxy->setWidget(m_combo);
}

void CountryComboBoxQmlAdapter::paint(QPainter * painter) {
QStyleOptionGraphicsItem style;
style.exposedRect = this->boundingRect();
m_proxy->paint(painter, &style, m_proxy->widget());
}
@

[Qnoobish]

What version of Qt are you using? Qt 5 ??

[philk]

5.1

[Qnoobish]

Sorry that i make another question but in your QML are you importing qtquick2 or qtquick1?

In case of Qtquick2, I am not sure that a QGraphicsProxyWidget works under Qt5 using QtQuickView classes to load your QML.

But I think your project builds and run so could you please post your code where you load your qml file and register this class?

[philk]

qtquick2. I will create a runnable test project and post it here

[JKSH]

Would it be easier to use a QML combobox?
http://qt-project.org/doc/qt-5.1/qtquickcontrols/qml-qtquick-controls1-combobox.html

[philk]

No, unfortunately not. This QML ComboBox is such a bad design. It uses a Popup Menu for the dropdown. Who would ever thought of that? Try to put a list of countries into a QML CB. Not only is it slow as hell, the menu it drops out is also unusable.

[Jens]

philk: Please file a proper bug or a feature if you are having issues with the qml ComboBox. There is no proper way to embed a widget in Qt Quick 2 so working around it that way is not recommended.

I am not aware of any performance issues with using a popup window in the combo box so a proper bug report with platform and info would be good. (on mac those combo box popups are native)

FYI I also started working on a patch against the dev branch that will enable an editable mode and initial keyboard-index support in ComboBox: https://codereview.qt-project.org/#change,63156

[philk]

the QML2 combo box does not use a popup window, it uses a popup menu That is the problem.

[Jens]

philk: That is an implementation detail and does not describe an actual problem. The QComboBox widget also uses a QMenu to show the actual popup as part of its implementation.

[philk]

Then this is a very awkward implementation on Qt side. Nowhere else (in Windows) a popup menu is used for Combo Dropdowns, for obvious reasons. Menus are not (easily) scrollable.