In my QMainWindow based application, I'm using two QQuickWidgets. One loads the map (using QML Map Type) and other one loads a custom scene. MainWindow also runs a QTimer at 10 Hz.
When I continuously zoom in/out on the map, at some point, the main window goes blank. This behavior is quite consistent. After resizing the main window, it gets refreshed but sometimes the qml scene is not rendered properly. Kindly have a look at the attached screenshots.
Why the main window goes blank and how to overcome it.
You can find working demo application on GitHub: github link
I'm using Desktop Qt 5.12.3 MinGW 64-bit.
Working App
Blank Main Window
Corrupted QML Scene
Related
Qt 5.12.6 MSVC2017 64-bit on Windows 10, Qt Creator 4.10.1.
I have a top level window derived from QMainWindow, which has a QMdiArea.
From the first main window I use a file open dialog to open a new document in a QMdiSubWindow and place it in the QMdiArea. After the file dialog returns but before I do the logic of opening the document, I have to call QApplication::setActiveWindow(this), to set it back to the main window, because the opening logic depends on the active window. The need for this somewhat appears related to https://www.qtcentre.org/threads/2950-ActiveWindow-changes-after-closing-QFileDialog in that the activeWindow becomes null, regardless of how I parent the file dialog.
I then open a second identical top level window and open another document using the same method.
What's very weird is that after the second QMdiSubWindow in the second QMainWindow is activated, the first QMainWindow gets activated again, and thus various follow-on operations affect the document in the first window rather than the second window which is the intended one. If I click back and forth on the main windows, the activation is correct.
If I create a new document directly from the second QMainWindow instead of using the file open dialog, then it works fine. The new QMdiSubWindow is created and shown in the second QMainWindow, without the first one getting activated. So this implicates the file dialog somehow.
When I put a breakpoint on a function triggered by the QMainWindow::activated signal, the stack trace shows this signal is coming from within Qt on its own accord, not from someplace in my code directly.
How can I find out why Qt is activating the first window when using the file dialog from the second window? At this point the code is too large to try to fit a minimal example here on SO.
--EDIT--
I added a one-shot QTimer at the end of the function that creates the QMdiSubWindow. Zero milliseconds after in creates the QMdiSubWindow it activates the first QMainWindow, then activates the current QMainWindow. That workaround seems to work, and the second QMainWindow becomes the active one. But only if I select away from it first. The fact that the hack works with 0 ms timer is also interesting. I'll be posting minimal example when I can.
thanks
This is a rare bug, but sometimes when I start my Qt app the qt3d window which hosts my scene is blank (without any of my models), except the window itself seems to be bugged because it will mirror other parts of the GUI if I shift between tabs. So instead of my scene appearing in the window it'll contain information and widgets from another tab that's located in the same area as the window on a different tab.
This doesn't occur very often, which makes the bug hard to replicate. Has anyone else seen this behavior before or maybe it's the way I'm setting up the Qt3DExtras::Qt3DWindow?
Qt3DExtras::Qt3DWindow* view = new Qt3DExtras::Qt3DWindow();
view->defaultFrameGraph()->setClearColor(QColor(0,0,0));
view->setRootEntity(CreateScene());
// embed 3D Window in Widget
QWidget* container = QWidget::createWindowContainer(view);
ui->verticalLayout_visualizer->addWidget(container);
I have inherited a Qt-based app that handles the master/detail relationship by presenting the detail screens as separate windows. The main window includes a list, and when you tap on a row a separate detail window is opened up.
In the code base, the detail windows are handled by a QML file and a matching .cpp file (the main window also has its own .cpp file). The problem I am facing is that a new client wants me to modify this application for them, except that they want everything to occur within a single window. They want the list to be shown on the left side, and then when a user taps a row, the detail screen is to be shown on the right side of the window in its own panel (but not in a separate window).
For various reasons I can't easily refactor this application. A quicker solution for me would be to continue to present the detail screen in its own window, but to make it a borderless window and position this borderless window over top of the main window (on the right) so that it appears to be a panel within the main window.
Is something like this possible with Qt? I have written Windows apps in the past that hooked into the Windows API to do something like, but I don't know whether this is even possible in a native Mac OS app, so I don't know whether Qt can handle it in some way automaticaly.
One thing you could try is to create a widget based "main" window and then use QWidget::createWindowContainer() to wrap the QtQuick windows for positioning them with QtWidget means, e.g. layouts.
I'm building the UI for an application using Qt and QML for Ubuntu Linux. I have a viewer window with a canvas element which is supposed to be fullscreen by default. On opening the application this works fine (i.e. Ubuntu sidebar and top taskbar are hidden). However, once I minimize my application and then maximize it again by using viewer->setFullScreen();, the Ubuntu sidebar and top taskbar are still visible and there is an offset while writing on the canvas due to the same.
Any help would be appreciated.
According to this topic on askubuntu, your problem do really looks like Unity bug (or feature). But, according to somehow related bug on Launchpad, it seems that you can get desired behavior by:
Turn "Always On Top" on via right-clicking the titlebar of your window, before making it go fullscreen.
This will prevent the Unity panel from rendering on top of this fullscreen-window, when using the other screen.
In Qt you can set Qt::WindowStaysOnTopHint to your window/widget via QWidget::windowFlags.
Pay additional attention to notes in official documentation:
This function calls setParent() when changing the flags for a window, causing the widget to be hidden. You must call show() to make the widget visible again.
About Qt::WindowStaysOnTopHint -- Informs the window system that the window should stay on top of all other windows. Note that on some window managers on X11 you also have to pass Qt::X11BypassWindowManagerHint for this flag to work correctly.
Hope this helps.
In my Qt symbian app, I have over ride the negative exit button with back to come back on main screen and then again over ride it with exit to close the app, my app is working fine on emulator but when I test it on device it shows exit button instead of back, some time it shows back also but if I go to the same page twice then again it start showing exit button, frustrating part is that app is working fine on Qt emulator but not on device. Does somebody knows whats the problem is. I am using
back->setSoftKeyRole(QAction::NegativeSoftKey);
this->addAction(back);
to over ride the exit button before loading the screen and
back->setSoftKeyRole(QAction::NegativeSoftKey);
this->removeAction(back);
to removing back button when coming back to mainWindow.
Create vertical layout and Widget which You will add on scrollarea with parent as that class this e.g
QVBoxLayout *vlay = new QVBoxLayout(this);
QWidget *area = new QWidget(this)
And add widget to it
This will make it child of parent class.
works fine for me.
I think adding and removing QAction objects here and there is asking for problems.
You should try to redesign your application to use a QStateMachine to handle transitions between states.
Take a look at the introductory documentation here.
Refer this LINK for custom softkeys..
QAction* myAction= new QAction(tr("My Action"), this);
myAction->setSoftKeyRole(QAction::NegativeSoftKey);
addAction(myAction);