@J-Hilk Thank you for answering the question.

@JonB Yeah, I was thinking of doing this because there are signals for both applicationDisplayNameChanged() & applicationNameChanged() this can provide me with an application-wide signal to change users. My application has different modules which are completely independent of each other (I have to develop a lot of custom applications where not each application has to have all modules, and so independent modules are the best idea), the common things among these modules are stored directly inside a namespace (every module is also inside this namespace) and so I need an application-level signal to propagate common settings for my application, i.e. current user master key, current font and current palette. For font and palette, QApplication provides the respective ..changed() signal but there is no way for me to add an application-level signal for the master user key without creating a singleton, which I very much want to avoid, that's why I was thinking of using applicationDisplayName as master user key :) @JonB @SGaist Thanks for the insight, I will figure out a different way then. P.S. It would be nice to have a void QCoreApplication::broadcast(const QString& string) signal, the string could be modified in different ways to provide different values to the broadcast :)

@Kent-Dorfman I'm sorry, but I steel don't get it...I have two physical monitors each of which is 1280x1024px. If they span into one display I should get a screen with 1280x2048 resolution, shouldn't I? But my screens list contains one an entity with {0, 1024, 1280, 1024} rect for available geometry. I can test what returns availableVirtualGeometry method tomorrow in the office, but no matter it does I can't find a way to render a GUI on the second physical monitor properly.

The Basic Drawing Example shows that. In your case, you'd likely just have to paint your image using the correct scaling information.

@MrCrackPotBuilder said in Detecting the removal of a screen and modifying the app accordingly.: Its also saying the same as before so I.m definitely going to have to use the QGuiApplication but how that i cant figure out... Yet you #include <QGuiApplication> in your class that than allows you access to the (unique) application instance pointer qApp than you can use that to update your Layout. QObject::connect(qApp, &QGuiApplication::screenCountChanged, this, &myClass::screenCountSlot);

Yeah, that looks ok. I wasn't suggesting to remove the flush permanently, just to see that the system background is drawing when you don't flush. Btw. Keep in mind that the system color can change at any time so if you want to be 100% correct you should either get it every time you render or handle the WM_SYSCOLORCHANGE and WM_THEMECHANGED messages.

Do you have that error on both platforms ? By the way, can post a minimal sample code that shows this behaviour ?

@SGaist Fixed it ;)

@ileonte Uh, i must use Qt5.3.1, coz our project demands this version....I think i have to read file to get target text string. Anyway, thank you~ :)

@jking said: @JKSH That is helpful information. I had only added the QThread into my flow after not having success creating the QGuiApplication directly in the JNI function. Even without the QThread (and no other created QObjects), the QGuiApplication constructor never returns. I will attempt to debug into QT's code and find where it is getting stalled, but I was hoping someone had an idea of what could be wrong. There are no error printouts from QT that I can see in logcat so my current working theory is that I am missing something from the setup of QtActivity in my Service that perhaps the constructor waits on instead of running into an error condition. My goal is to have my service initialize several manager classes (which utilize qt signals and slots) and then continue to use the QGuiApplication in my main function when the QtActivity is started. Those are interesting symptoms. Sorry I'm not able to help you more with this. I suggest you subscribe to the Interest mailing list and ask there -- you can find Qt engineers on that list, who probably know more. Good luck!

oh i solved my question, int QDesktopWidget::screenNumber(const QPoint & point) const