How to get the target window of QTouchEvent
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In qt5 there is a QTouchEvent::window() method to get which QWindow this touch event will be sent to, in Qt6 this interface has been removed, what can I do to replace it?
I've tried using this way:
QObject* target = te->target(); QWindow* targetWindow; if (target->isWindowType()) targetWindow = dynamic_cast<QWindow*>(target); else { WId wid = static_cast<QWidget*>(target)->winId(); targetWindow = QWindow::fromWinId(wid); }but I've found that the result isn't entirely accurate, and the first time I receive QTouchEvent, I get an error QWindow instead of the QWidgetWindow I expected
@Wei-Wei You can use https://doc.qt.io/qt-6/qtouchevent.html#target and then check whether you can cast it to QWidget* if you can use https://doc.qt.io/qt-6/qwidget.html#window
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@Wei-Wei You can use https://doc.qt.io/qt-6/qtouchevent.html#target and then check whether you can cast it to QWidget* if you can use https://doc.qt.io/qt-6/qwidget.html#window
wrote on 26 Jul 2023, 02:04 last edited by@jsulm The return of https://doc.qt.io/qt-6/qwidget.html#window is a QWidget*, but i need a QWindow*
I find i can get the right window like this:
// target is a QObject* such as a event receiver QWidget* targetWidget = static_cast<QWidget*>(target); targetWindow = targetWidget->window()->windowHandle(); -
@jsulm The return of https://doc.qt.io/qt-6/qwidget.html#window is a QWidget*, but i need a QWindow*
I find i can get the right window like this:
// target is a QObject* such as a event receiver QWidget* targetWidget = static_cast<QWidget*>(target); targetWindow = targetWidget->window()->windowHandle();Just a side-note to casting: in Qt world you can use
qobject_cast<>(), it's as fast as static cast but as flexible as dynamic cast. Works only on subclasses of QObject. -
Just a side-note to casting: in Qt world you can use
qobject_cast<>(), it's as fast as static cast but as flexible as dynamic cast. Works only on subclasses of QObject. -
@jsulm The return of https://doc.qt.io/qt-6/qwidget.html#window is a QWidget*, but i need a QWindow*
I find i can get the right window like this:
// target is a QObject* such as a event receiver QWidget* targetWidget = static_cast<QWidget*>(target); targetWindow = targetWidget->window()->windowHandle();@Wei-Wei said in How to get the target window of QTouchEvent:
is a QWidget*, but i need a QWindow*
Please read again what I wrote...
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@Wei-Wei said in How to get the target window of QTouchEvent:
is a QWidget*, but i need a QWindow*
Please read again what I wrote...
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@jsulm emmm，like this？
if (event->target()->isWidgetType()) { QWidget* targetWidget = qobject_cast<QWidget*>(event->target()); QWidget* window = targetWidget->window(); }@Wei-Wei Yes, but you also should always check pointers after casting. Casting can fail you then end up dereferencing an invalid pointer...
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@Wei-Wei Yes, but you also should always check pointers after casting. Casting can fail you then end up dereferencing an invalid pointer...
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@jsulm After I checked that isWidgetType() is true, cast can still fail? Is a bug of Qt?
And thank you for the ideas, i find "QMutableEventPoint::window(const QEventPoint &)" that solved my problem.
wrote on 27 Jul 2023, 08:09 last edited by@Wei-Wei said in How to get the target window of QTouchEvent:
@jsulm After I checked that isWidgetType() is true, cast can still fail? Is a bug of Qt?
Maybe, maybe not, But for the sake of an extra statement you should always check the return result of a
qobject_cast<>()or adynamic_cast<>()as a matter of course.Q_ASSERT(targetWidget);would suffice if you're sure it should be true. -
@Wei-Wei said in How to get the target window of QTouchEvent:
@jsulm After I checked that isWidgetType() is true, cast can still fail? Is a bug of Qt?
Maybe, maybe not, But for the sake of an extra statement you should always check the return result of a
qobject_cast<>()or adynamic_cast<>()as a matter of course.Q_ASSERT(targetWidget);would suffice if you're sure it should be true. -
wrote on 27 Jul 2023, 08:57 last edited by
I found QMutableEventPoint::window(const QEventPoint &) can solve my problem.
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W Wei Wei has marked this topic as solved on 27 Jul 2023, 09:19
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