Hi Rafael, I was looking at this today and I am also a bit puzzled about why the QWidget stays on the screen. It might have something to do with the 4 platform windows that are created for each top level QWidget.
Does anyone btw. know why this is necessary? About the behaviour of "setScreen". I too find it a bit awkward that it hides the window. If we can't change this any more, than it should at least be mentioned in the documentation. Fabian ________________________________________ From: [email protected] [[email protected]] on behalf of Alan Alpert [[email protected]] Sent: Saturday, April 12, 2014 2:16 AM To: Rafael Roquetto Cc: Qt Project Development Mailing-List Subject: Re: [Development] QWindow::setScreen() and QQuickWindow On Fri, Apr 11, 2014 at 12:56 PM, Rafael Roquetto <[email protected]> wrote: > Hello, > > I have been investigating an interesting bug (using QNX as the platform for > Qt). Here is a brief summary: > > (all code inside main() and before app.exec()) > > QQuickView v; > v.setScreen(someSecondScreen); > v.show(); // works as expected > > but > > QQuickView v; > v.show(); > v.setScreen(someSecondScreen); // window is never shown > > Is this the expected behavior? Yes. setScreen expects to destroy the backing window and recreate it, so it passes onto users the expectation that they will have to reset all window properties afterwards. I'm not sure what QQuickView should do, but in the declarative case where you might have a "Window { visible: true; visibility: Window.FullScreen }" it would be expected to reset all the properties to what's in QML. I doubt it does that yet, and that's a bug ;) . > The reason this happens is because > QWindow::setScreen() calls destroy(), which triggers setVisible(false). > Afterwards, it calls create() but create() never bothers to display the window > again. In other words, it does > > QWindow::setVisible(true) //coming from show(); > QWindow::setVisible(false) //coming from setScreen() -> destroy() > > For some reason beyond my knowledge, QtWidgets do not suffer for this bug, > i.e.: > > QWidget w; > w.setScreen(secondScreen); > w.show(); // works! > > and > QWidget w; > w.show(); > w.setScreen(secondScreen); // also works > > I digged a bit inside the QWidget code and it also follows the pattern of > having setVisible(true) followed by setVisible(false) called, just like in the > QQuickWindow case. However, something is happening that in spite of that the > widget is being shown regardlessy. > > Any thoughts? Comments? Last time I was playing around with multiwindow support (about a year ago), QNX was the only platform where setScreen worked reliably. So the strange stuff happening could be related to the platform implementation, as we have no other platforms to compare it with. It also makes it hard to determine the "correct" multi-screen API, when there's no clear picture of how it would work on the majority of platforms. -- Alan Alpert _______________________________________________ Development mailing list [email protected] http://lists.qt-project.org/mailman/listinfo/development _______________________________________________ Development mailing list [email protected] http://lists.qt-project.org/mailman/listinfo/development
