For a kind of CAD application I first create a QWidget (intended as a 2D editor) with mouse tracking enabled in a tab of QTabWidget. Drawing and moving lines is super fast as expected.
Next I create a new tab with an QOpenGLWidget (intended as a 3D view). No mouse tracking, but it reacts super fast to mouseMoveEvent() when button pressed. As expected.
Now when I switch the tab back to the QWidget mouseMoveEvents become very slow. WHY? Switching back to GL shows that the QOpenGLWidget still reacts fast.
I inserted QDebug output to paintGL() - it's not called. Next I uncommented all of the code in initializeGL(), resizeGL() and paintGL(), so no GL code at all remains. Still the same problem!
Qt version is 5.5.1 running on Ubuntu 14.04.5 LTS.
Related
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
I have a small Qt Desktop application (in C++) which I need to make it work in a touch screen device running Window 10. The device has a touchscreen and application works perfectly with keyboard and mouse.
I am not expert in developing Qt Application and that's why unable to resolve this could be silly isssue.
However, when I try to use touchscreen, the last touched QToolbutton remain pressed even if I have moved my finger away from the touchscreen and when I touch somewhere else, then that QToolButton is released.
I expect the Qtoolbutton to behave just like when it is pressed using a mouse. Once I move my finger off the touchscreen, it should be released.
I tried to resolve this issue with the following:
btn->setAttribute(Qt::WA_AcceptTouchEvents);
And
qApplication.setAttribute(Qt::AA_SynthesizeMouseForUnhandledTabletEvents);
But it didn't help. I think I am missing a very small issue and after that Qt will handle all the touch related events on it's own and will show the right behavior.
I am cross-compiling on my Ubuntu machine using MXE. Qt version is 5.12.
I think I am missing a very small issue and after that Qt will handle all the touch related events on it's own and will show the right behavior.
QWidget subclasses, including QToolButton, do not handle touch events on its own. It is not even needed that Qt emulate mouse events. You are seeing the effects in your application of emulated mouse events synthesized by Windows. This makes possible for ancient Windows programs designed to be used with mouse will work somewhat in modern touch enabled Windows tablets. But the mouse emulation is hardly perfect.
If the behavior is unacceptable for the QToolButton class, you have the option of subclass it and handle touchevents as you see fit, overriding mouse events as well, to avoid the synthesized events to be handled as well.
I had the same problem. I solved it by changing the signal to which the slot is connected.Previously I was connected my slot to QPushButton::pressed. To fix it, change the connect to use the signal QPushButton::clicked:
connect(my_button, &QPushButton::clicked, this, &MyClass::onMyButtonClicked);
I have a C++ Qt 4 application written for Raspberry Pi. I'm experiencing an odd side-effect of showing a QMessageBox and I don't know enough about Qt to debug it.
The pi has a touchscreen, so I launch the application with unclutter to hide the mouse cursor. (Though this doesn't affect my issue... I have tried without unclutter just in case.)
I have sub-classed QLineEdit to override focusInEvent() and focusOutEvent() to select-all when a LineEdit gets focus, and deselect-all when it loses focus.
Before showing any QMessageBoxes, everything works perfectly - tapping on a QLineEdit selects all the text; tapping the next one de-selects the previous QLineEdit, and selects the new QLineEdit.
After showing a QMessageBox, my overridden events stop working, and QLineEdits no longer auto-select and de-select.
If I add:
msgBox.setWindowFlags(msgBox.windowFlags() | Qt::Popup);
before I exec() the QMessageBox, then text highlighting continues working normally, but the cursor is displayed and flickers while the QMessageBox is on the screen.
It seems like there is a side-effect of showing the QMessageBox that affects the calling window and my sub-classed QLineEdit boxes... but not if the QMessageBox has the Popup flag set!
I've tried storing and manually re-loading the flags on the main window, and that does nothing, so it doesn't appear to be flags on the main window.
One more oddity: everything works fine if I run the application remotely over XMing and SSH... it's only when it's run locally on the Pi in plain-old X11 that it freaks out.
Any thoughts on how to debug this? Thank you!
I was able to work around this by doing two things.
First, I updated the flags of the QMessageBox before opening it:
msgBox.setWindowFlags(Qt::Popup);
msgBox.exec();
and second, I hid the cursor in Qt code, rather than relying on Unclutter; this fixed the flickering cursor issue:
QApplication::setOverrideCursor(Qt::BlankCursor);
My application has non-rectangular popup widgets.
their class defines the following to achieve that transparency:
setAttribute(Qt::WA_NoSystemBackground, true);
setAttribute(Qt::WA_TranslucentBackground, true);
I also use:
this->setWindowFlags(Qt::Popup| Qt::FramelessWindowHint);
The problem is that on windows 7, an automatic "shadow" is being drawn on the bottom and right sides of my window. This is highly undesirable.
So, I tried using Qt::Tool instead of Qt::Popup
this->setWindowFlags(Qt::Tool | Qt::FramelessWindowHint);
This works visually. No shadow, but now a mouse click outside my widget window will not automatically close/hide it as it would have done with a Qt::Popup.
So, I need one of these two solutions:
A way to have Qt::Popup and get rid of that automatic windows shadow decoration
A way to let the Qt::Tool window a mouse click occurred outside of it.
One note: My application is built for Windows XP and up. I cannot use a Vista/Win7 only runtime DLLs, nor can i have a "Windows XP" and "Vista and up" separate builds.
Any advice will be welcome.
You could manually watch for when the focus changes from your Qt::Tool window. So basically you watch for when the focus goes onto another window of your process or when your application loses focus.
How to detect that my application lost focus in Qt?
Hope that helps.
Finally after realizing that no amount of "SetFocusPolicy" calls will allow me to receive those events for a Qt::Tool window, I've resorted to something else to fix my problem:
I kept the Qt:tool as Qt::Popup caused an undesired shadowing effect, tarnishing my owner draw frame. Removing this style cannot be done in Qt and I didn't want to mess with platform specific conditional code.
I installed an event filter with my Qt::tool window and I began receiving events that assisted me in understanding when other parts of my application were clicked, or if the application itself lost focus to another application. This was what I needed, functionality wise. I could also get an event when users click the non-client areas of the application's main window, such as the windows caption so that I can close it when dragging begins etc.
My solution for Windows 7:
QDialog *d = new QDialog;
d->setStyleSheet("background:transparent;");
d->setAttribute(Qt::WA_DeleteOnClose, true);
d->setAttribute(Qt::WA_TranslucentBackground, true);
#ifdef Q_OS_WIN
d->createWinId();
#endif
d->setWindowFlags(Qt::Popup | Qt::FramelessWindowHint);
d->show();
I set my QListView
d->setWindowFlags(Qt::Popup | Qt::FramelessWindowHint);
Install eventfilter and used MousePressEvent to hide qlistview widget.
MousePressEvent on list never comes to filter they produce other events which I didn't debug.
So if you want to design auto completer this will be perfect. Tested in Qt5.3.1.
I am trying to implement a custom OpenGL scene (wrapped in a QGLWidget), but still use QT controls (such as slide bars and buttons). I tried to make my main widget a QGLWidget, which has QWidgets as children. The child widgets seem to work (when I click a pulldown menu, its options appear), but the widget fails to draw (I see a white square). I changed the base class of my children widgets from QWidget to QGLWidget, and now QPainter calls work, but QT GUI stuff is still not displaying...
Some claim that a QGLWidget can not have QWidgets as children... I am not sure about that and I'm not willing to give up. By the way, I am using Visualization Library to draw the OpenGL scene, but it is just an OpenGL wrapper...
Any clues where the problem might be? Also, key events stop being processed for some reason when I add subwidgets to the GQLWidget.
Update:
I tried various combinations of widgets and layouts. It seems that the QGLWidget just gets drawn on top of anything. I even tried with raise() to arrange Z-depth of the widgets, to no avail. Is overlayGL() the only way to draw on top of an OpenGL widget?
Update 2
After months of trying, I figured out it is something related to QT. Whenever a QGLWidget is drawn on top of another QGLWidget, the first's background() function is not called. So a button is there and can be clicked, but it's not drawn. My workaround was to draw everything myself using QPainter - that works. What I found curious is, one has to use QPainter::startNativePainting() in order to draw with it. One would expect that they would overload start() in QPainter to call startNativePainting() whenever a QGLWidget is the painting device...
Another (maybe useful) fact is that QPainter calls CHANGE the Opengl context. So if you have another tool in cooperation with QPainter (in my case Visualization Library), chances are that one of them will crash (in my case VL which checks if the context state has been cleared before each frame).
There is a labs example of rendering Qt widgets using opengl it's a little old and I haven't tried it with the improved qglwidget in 4.8
There is also an issue with drawing over the top of a fullscreen QGLwidget - it was supposedly a bug in NVidia's openGL driver. It doesn't seem to have been resolved
https://bugreports.qt-project.org/browse/QTBUG-7556
If I were you I would use the QGLWidget as a viewport for a QGraphicsScene, then you can draw your widgets using a QGraphicsProxyWidget. That way you get a proper OpenGL viewport with the ability to put widgets in and manipulate them easily.
Did u try to call update() explicitly? I find that sometimes QGLWidget update the display stuff kind of slow.
This is an old question, but I recently had quite a bit of trouble with this, and this is what helped me -
Use QML/QT Quick. QML is a javascript-like language that allows you to layout your widget elements on a window and do basic processing on events like mouse clicks. There are a few other cool features, but the one that is most relevant to this question is that you can import qt widgets from C++ code.
So you can make a custom QGLWidget, import it into the QML window, and set the size/position/stick widgets on top of it in whatever you want, very easily. QT's Scenegraph example does a great job explaining this. Scenegraph's code is also included as an example in at least Qt Creator 3.2.1 Open Source (that's the version I have anyway)