Opening a QPrintDialog needs a pointer to parent widget but:
I have a QQuickApplication that is based on QGuiApplication that is QCoreApplication extend for non Widget apps.
My app window cannot be interpreted as a Widget. so is there any way?
I wonder why there is no QML type of this facility!
Thanks in advance
Note that the signature is
QPrintDialog(QPrinter *printer, QWidget *parent = nullptr);
indicating that the parent argument is optional. So
QPrintDialog myPrintDialog(myPrinter);
is totally fine.
Related
I am using Qt5 beta and trying to embed a QWidget-based object into QML. The goal is to use QML as much as possible, and only use QWidget objects where QML does not do what I need. I found a link explaining how to do this for Qt4.7, but I have not found any information explaining how to do this in Qt5.
http://doc.qt.digia.com/4.7/declarative-cppextensions-qwidgets.html
The same example is also available in the Qt5 examples folder under:
examples\qtquick1\declarative\cppextensions\qwidgets
Unfortunately, this example uses QtQuick 1, rather than QtQuick 2, and I would like to use the new features of Qt5. I actually want to embed a qwt widget, but as a first step I would be happy to embed any simple QWidget-based object.
Can anybody help me get the example working under Qt5 / QtQuick 2 ?
Qt Quick 2 uses a scene graph for efficient rendering on the GPU. Unfortunately this makes it impossible to embed classic widgets into the scene. The old approach to embed such widgets with the help of QGraphicsProxyWidget works only with Qt Quick 1, because internally it uses a QGraphicsView for all the heavy lifting and QGraphicsProxyWidget is meant to be used with it.
As of now there are no plans to enable embedding classic QWidgets into the scene graph I know of. I think this is rather unlikely to change, because the concepts of QPainter, the painting framework used for the classic widgets, and the new scene graph doesn't play well with each other.
There some efforts to develop new widgets sets specifically tailored for the needs of QML, but none of them are as powerful and mature as the classic widgets. The most prominent ones are the QML Quick Controls, bundled with Qt since version 5.1.
If you really depend on QWT my advice would be to stick with Qt Quick 1.1 for now. It's still bundled with Qt 5, probably for cases like yours. That way you won't take advantage of the new scene graph, though.
You can embed QWidget to QML by using QQuickPaintedItem class:
http://doc.qt.io/qt-5/qquickpainteditem.html
Qt5 has an example:
http://doc.qt.io/qt-5/qtquick-customitems-painteditem-example.html
You should implement an inherent of QQuickPaintedItem with private widget attribute, that you want to embed. Provide paint method, that just render the QtWidget and provide mouse and other event transmitting from inherit of QQuickPaintedItem to embed QtWidget.
There's also QSG (Qt scene graph API), but my experience with that thing wasn't smooth. I believe the clue in multithreading (performing rendering in the different thread (not the Qt GUI thread one, however on Windows that's not true and all is done in main GUI thread).
I've implemented embedding of QCustomPlot, here's link: github.com/mosolovsa/qmlplot
What could be done is to render the widget to an image and upload as texture.For interaction someone needs to forward events like mouseClick or keyPressed from the sceneGraph, translate to widget coordinates, pass on, render and upload texture again. Just an idea :)
The recommended approach is to stay with a QWidget based application and embed the QML parts using QWidget::createWindowContainer.
Further to Julien's answer - a simple way to achieve this is to use QQuickWidget to display the QML scene, and then add a regular QWidget as a child of the QQuickWidget. You can also add a simple intermediate QObject to anchor the QWidget to an item in the scene.
E.g.:
In main.qml:
Item {
... // layouts, extra items, what have you
Item
{
objectName: "layoutItem"
anchors.fill: parent
}
... // more layouts, extra items, etc.
}
widgetanchor.h:
class WidgetAnchor: public QObject
{
ptr<QWidget> _pWidget;
QPointer<QQuickItem> _pQuickItem;
public:
WidgetAnchor(QWidget* pWidget, QQuickItem* pItem)
: QObject(pWidget), _pWidget(pWidget), _pQuickItem(pItem)
{
connect(_pQuickItem, &QQuickItem::xChanged, this, &WidgetAnchor::updateGeometry);
connect(_pQuickItem, &QQuickItem::yChanged, this, &WidgetAnchor::updateGeometry);
connect(_pQuickItem, &QQuickItem::widthChanged, this, &WidgetAnchor::updateGeometry);
connect(_pQuickItem, &QQuickItem::heightChanged, this, &WidgetAnchor::updateGeometry);
updateGeometry();
}
private:
void updateGeometry()
{
if (_pQuickItem)
{
QRectF r = _pQuickItem->mapRectToItem(0, QRectF(_pQuickItem->x(), _pQuickItem->y(), _pQuickItem->width(), _pQuickItem->height()));
_pWidget->setGeometry(r.toRect());
}
}
};
In main.cpp:
int main(int argc, char *argv[])
{
QApplication app(argc, argv);
auto pqw = new QQuickWidget;
pqw->setSource(QUrl::fromLocalFile("main.qml"));
pqw->setResizeMode(QQuickWidget::SizeRootObjectToView);
pqw->setAttribute(Qt::WA_DeleteOnClose);
auto pOwt = new MyWidget(pqw);
if (auto pOverlayItem = pqw->rootObject()->findChild<QQuickItem*>("overlayItem"))
new WidgetAnchor(pOwt, pOverlayItem);
pqw->show();
return app.exec();
}
The documentation states that using QQuickWidget has advantages over QQuickView and QWidget::createWindowContainer, such as no restrictions on stacking order, but has a 'minor performance hit'.
Hope that helps.
I am using Qt5 beta and trying to embed a QWidget-based object into QML. The goal is to use QML as much as possible, and only use QWidget objects where QML does not do what I need. I found a link explaining how to do this for Qt4.7, but I have not found any information explaining how to do this in Qt5.
http://doc.qt.digia.com/4.7/declarative-cppextensions-qwidgets.html
The same example is also available in the Qt5 examples folder under:
examples\qtquick1\declarative\cppextensions\qwidgets
Unfortunately, this example uses QtQuick 1, rather than QtQuick 2, and I would like to use the new features of Qt5. I actually want to embed a qwt widget, but as a first step I would be happy to embed any simple QWidget-based object.
Can anybody help me get the example working under Qt5 / QtQuick 2 ?
Qt Quick 2 uses a scene graph for efficient rendering on the GPU. Unfortunately this makes it impossible to embed classic widgets into the scene. The old approach to embed such widgets with the help of QGraphicsProxyWidget works only with Qt Quick 1, because internally it uses a QGraphicsView for all the heavy lifting and QGraphicsProxyWidget is meant to be used with it.
As of now there are no plans to enable embedding classic QWidgets into the scene graph I know of. I think this is rather unlikely to change, because the concepts of QPainter, the painting framework used for the classic widgets, and the new scene graph doesn't play well with each other.
There some efforts to develop new widgets sets specifically tailored for the needs of QML, but none of them are as powerful and mature as the classic widgets. The most prominent ones are the QML Quick Controls, bundled with Qt since version 5.1.
If you really depend on QWT my advice would be to stick with Qt Quick 1.1 for now. It's still bundled with Qt 5, probably for cases like yours. That way you won't take advantage of the new scene graph, though.
You can embed QWidget to QML by using QQuickPaintedItem class:
http://doc.qt.io/qt-5/qquickpainteditem.html
Qt5 has an example:
http://doc.qt.io/qt-5/qtquick-customitems-painteditem-example.html
You should implement an inherent of QQuickPaintedItem with private widget attribute, that you want to embed. Provide paint method, that just render the QtWidget and provide mouse and other event transmitting from inherit of QQuickPaintedItem to embed QtWidget.
There's also QSG (Qt scene graph API), but my experience with that thing wasn't smooth. I believe the clue in multithreading (performing rendering in the different thread (not the Qt GUI thread one, however on Windows that's not true and all is done in main GUI thread).
I've implemented embedding of QCustomPlot, here's link: github.com/mosolovsa/qmlplot
What could be done is to render the widget to an image and upload as texture.For interaction someone needs to forward events like mouseClick or keyPressed from the sceneGraph, translate to widget coordinates, pass on, render and upload texture again. Just an idea :)
The recommended approach is to stay with a QWidget based application and embed the QML parts using QWidget::createWindowContainer.
Further to Julien's answer - a simple way to achieve this is to use QQuickWidget to display the QML scene, and then add a regular QWidget as a child of the QQuickWidget. You can also add a simple intermediate QObject to anchor the QWidget to an item in the scene.
E.g.:
In main.qml:
Item {
... // layouts, extra items, what have you
Item
{
objectName: "layoutItem"
anchors.fill: parent
}
... // more layouts, extra items, etc.
}
widgetanchor.h:
class WidgetAnchor: public QObject
{
ptr<QWidget> _pWidget;
QPointer<QQuickItem> _pQuickItem;
public:
WidgetAnchor(QWidget* pWidget, QQuickItem* pItem)
: QObject(pWidget), _pWidget(pWidget), _pQuickItem(pItem)
{
connect(_pQuickItem, &QQuickItem::xChanged, this, &WidgetAnchor::updateGeometry);
connect(_pQuickItem, &QQuickItem::yChanged, this, &WidgetAnchor::updateGeometry);
connect(_pQuickItem, &QQuickItem::widthChanged, this, &WidgetAnchor::updateGeometry);
connect(_pQuickItem, &QQuickItem::heightChanged, this, &WidgetAnchor::updateGeometry);
updateGeometry();
}
private:
void updateGeometry()
{
if (_pQuickItem)
{
QRectF r = _pQuickItem->mapRectToItem(0, QRectF(_pQuickItem->x(), _pQuickItem->y(), _pQuickItem->width(), _pQuickItem->height()));
_pWidget->setGeometry(r.toRect());
}
}
};
In main.cpp:
int main(int argc, char *argv[])
{
QApplication app(argc, argv);
auto pqw = new QQuickWidget;
pqw->setSource(QUrl::fromLocalFile("main.qml"));
pqw->setResizeMode(QQuickWidget::SizeRootObjectToView);
pqw->setAttribute(Qt::WA_DeleteOnClose);
auto pOwt = new MyWidget(pqw);
if (auto pOverlayItem = pqw->rootObject()->findChild<QQuickItem*>("overlayItem"))
new WidgetAnchor(pOwt, pOverlayItem);
pqw->show();
return app.exec();
}
The documentation states that using QQuickWidget has advantages over QQuickView and QWidget::createWindowContainer, such as no restrictions on stacking order, but has a 'minor performance hit'.
Hope that helps.
In the QObject.__init__(self, Parent=None) documentation it states:
The parent argument, if not None, causes self to be owned by Qt instead of PyQt.
What does it mean to be owned by Qt instead of PyQt? Does this have effects on behavior that I should be aware of when developing a PyQt application?
Yes, It is. It have Effects to before create any object in PyQt application. If we set parent QWidget None, I can be tell this QWidget is top-level window. I will try explain;
"Parent Widget equivalent like frame of windows"
Parent Widget of QMainWindow is none. Then, owned by Qt instead of PyQt (or easy word root). Parent Widget of QWidget (in red) is QMainWindow, Then geometry reference by QMainWindow. Parent Widget of QPushButton is QWidget (Green), Then geometry reference by QWidget (Green). And all widget as same ...
So, QMainWindow have fully control widget in your child. For example, If self delete, All child will follow delete too. etc.
But, If we set Parent Widget of QWidget (in red) is None, that mean this QWidget like new window. Like this picture;
For now, we have 2 top-level window. But QWidget have independent with QMainWindow. If self delete, All child will follow delete too but not outside QMainWindow. Outside QWidget not delete. So, some application have create many widget, but it will has main widget in main menu to control child.
Not only frame of windows, It just Example & Comparison.
Regards,
if i need multiple dialogs for my application. QmainWindow is just for layout of multiple dialogs?
QMainWindow is still a single window but it provides facilities for advanced GUI programming.
If you need to pop up multiple dialogs first read Modeless Dialogs section of qt docs.
If basically says that create your dialogs on the heap and use show() method.
Something like below (untested code). This should show two dialogs at the same time.
int main( int argc, char ** argv )
{
QApplication app;
Mydialog1 dlg1 = new Mydialog1();
dlg1->show ();
Mydialog1 dlg2 = new Mydialog2();
dlg2->show ();
a.exec();
}
Yes, a QMainWindow provides a the base window for a regular GUI application. A regular GUI application is thought of as having "Menus", "Toolbars", "Status bar"
AFAIK, a QDialog does not provide any of the above. if your application doesn't require any menus, toolbars etc... then you can simply use QDialogs as you said. But I'd strongly recommend using a QMainWindow if your application has multiple widgets. If you can explain what you are trying to achieve then maybe we can help you with better alternatives.
I have a QWidget container that contains my custom widget. This QWidget container was promoted to the custom widget I created. I have a QPushButton on my MainWindow.ui. I want to connect this QPushButton to the promoted QWidget. How will I do this?
For example, I have a function on my promoted QWidget class, and I want to call this function when I click the QPushButton located at the MainWindow.ui.
Thanks in advance!
Have you considered using a connect??
connect the QPushButton singal clicked to that function (make sure its a slot where its declared).