I just updated my opencv to the latest stable version (3.1.0). I tried to run a programm on which i'm working for a long time now, and everything works fine.
But I've got a new output 'Init done - Opengl support available'coming from Qt or OpenCV I don't really know, when I'm displaying an image. I would like to disable that output, because I've already a lot of outputs of mine.
If you have a quick solution (I mean easy to process), it would be great
Thanks
Looking at the relevant code, this output is only triggered if there is no QApplication instance already present. You can stop the output by creating a QApplication instance before doing any OpenCV related operations:
int main(int argc, char *argv[]) {
QApplication app(argc, argv);
// Perform highgui operations.
}
Related
I got stuck with the problem that my application on some PCs loads the processor very heavily, and does not load the video card at all. When I went to figure it out, I came across this article: https://www.qt.io/blog/2017/01/18/opengl-implementation-qt-quick-app-using-today
It describes the method of debugging, and says that it is necessary to set the value of the environment QSG_INFO = 1. Current I do not quite understand where it needs to be done.
To set an environment variable you can use qputenv():
#include <QtGlobal>
int main(int argc, char *argv[]) {
qputenv("QSG_INFO", "1");
QGuiApplication a(argv, argc);
// ...
or you can set when launching the executable:
QSG_INFO=1 ./your_executable
If you are running your application from Qt Creator you can add/overwrite environment variables from the Project tab:
Look at this Qt doc for more info.
I'm currently developing a Console Unit Test Client with Google Test.
The Tests involves a step where a binary file is downloaded from a server.
To download this file I thought about using Qt.
Now I took the example code from
https://wiki.qt.io/Download_Data_from_URL
This gives me the error QEventloop canot be used without QApplication
I found this thread QEventLoop: Cannot be used without QApplication
However this works for a UI application.
My googletest main is predefined
GTEST_API_ int main(int argc, char **argv) {
printf("Running main() from %s\n", __FILE__);
testing::InitGoogleTest(&argc, argv);
return RUN_ALL_TESTS();
}
Where would be a good place to add the QApplication?
Could you help me out?
thx for your help :)
I am running a small app on KDE Plasma 5 created with Qt and the KDE framework. Almost everything works like a charm, just one part doesn't work. I just cannot set the application display name. I have the following code:
int main(int argc, char **argv) {
QApplication application(argc, argv);
KLocalizedString::setApplicationDomain("blender-render-control");
KCrash::initialize();
KAboutData aboutData(QStringLiteral("blender-render-control-center"),
i18n("Blender Render Control Center"),
QStringLiteral("1.0"),
i18n("A simple application to control the blender render control server"),
KAboutLicense::Custom,
i18n("Copyright 2019, Knerd <knerd#knerd.knerd>"));
aboutData.addAuthor(i18n("Knerd"), i18n("Author"), QStringLiteral("knerd#knerd.knerd"));
aboutData.setOrganizationDomain("knerd.knerd");
aboutData.setDesktopFileName(QStringLiteral("knerd.knerd.blender-render-control"));
KAboutData::setApplicationData(aboutData);
QApplication::setWindowIcon(QIcon::fromTheme(QStringLiteral("knerd.knerd.blender-render-control")));
application.setApplicationDisplayName(i18n("Blender Render Control Center"));
application.setApplicationName(i18n("Blender Render Control Center"));
QCommandLineParser parser;
aboutData.setupCommandLine(&parser);
parser.process(application);
aboutData.processCommandLine(&parser);
auto *window = new MainWindow();
window->show();
return QApplication::exec();
}
From reading the docs and checking some examples, this should set the application title in my KDE environment. But it doesn't, the application name is the name of the executable.
Is this a bug in KDE or am I doing something wrong?
I have a GUI application written using Qt Widgets. I've added versioning and I'm planning to write an update manager too. In order this to work the update manager must be able to determine the version of my app. I thought of implementing this by running my app with a version switch then parsing it's output. I did a research and I found out that Qt has some kind of built in solution for this.
Here is an example:
#include "mainwindow.h"
#include <QApplication>
#include <QCommandLineParser>
int main(int argc, char *argv[])
{
QApplication app(argc, argv);
QApplication::setApplicationVersion("1.0.0");
QCommandLineParser parser;
auto versionOption = parser.addVersionOption();
parser.process(app);
if (parser.isSet(versionOption))
{
MainWindow w;
w.show();
return app.exec();
}
return 0;
}
If I launch this app with a -v or --version command line switch, I get a message box containing the version information.
I need to achieve the same, only the information should be printed to standard output. If the app is launched with the version switch it should only display the version in the console then close.
How could I print the version information to the standard console output with a GUI app?
As we cleared some points in comments let's move on. ;)
Take a look at the documentation (http://doc.qt.io/qt-5/qapplication.html#details). In the detail section you see a sane way how to properly parse and handle command line options.
And here (https://stackoverflow.com/a/3886128/6385043) you can see a possibility for writing to standard output. Notice the QDebug caveat.
In my opinion, stick to the text file. You may generate it during build with qmake using the variable VERSION, which you can also use with QApplication::setApplicationVersion(QString).
I'm using Qt5.1 and I'm trying to create a QApplication without a display. I need to draw text with QPainter, so I need to use QApplication (or QGuiApplication), otherwise I get a segfault.
The application worked fine in Qt4.8, but fails in Qt5.1 on a headless version of Ubuntu with the error:
"QXcbConnection: Could not connect to display".
In Qt 4.8, I was able to use the following constructor with GUIenabled = false to create a QApplication that did not require a display:
QApplication::QApplication ( int & argc, char ** argv, bool GUIenabled )
In Qt5.1, the constructor for QApplication no longer has the GUIenabled flag.
I scanned the source code briefly, and there does seem to be a flag in the QApplication constructor, but it is undocumented as to what options can be used in that flag. Using "false" does not work.
How can I create a QApplication without a display? Is there an alternative method to telling QApplication GUIenabled = false? Alternatively, can I create a QCoreApplication that will not segfault when drawing text with QPainter on a QImage?
Yes, that's a Qt 3 (?) thing that is gone in Qt 5. Try running your application with the -platform offscreen command line option instead.
Note that you don't need QApplication or linking to QtWidgets to just draw upon a QImage, using QGuiApplication (and linking to QtGui) is sufficient.
If you want to create an app without GUI, you need to use QCoreApplication instead of QApplication.
Just hit this same issue. Really annoying that it at least isn't a compile error. My solution was just to use pointers and heap objects like,
QCoreApplication* app = 0;
Display* display = XOpenDisplay(NULL);
if (display)
{
XCloseDisplay(display);
app = new QApplication(argc, argv);
qobject_cast<QApplication*>(app)->setQuitOnLastWindowClosed(false);
}
else
{
app = new QCoreApplication(argc, argv);
}
return app->exec();