Image processing error

Re: Image processing error

Did you initialize the imageLabel pointer with a QLabel instance? Can you show us the code where you did that?

Re: Image processing error

I did.

Code:

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
 
    imageLabel = new QLabel;
    imageLabel->setBackgroundRole(QPalette::Base);
    imageLabel->setSizePolicy(QSizePolicy::Ignored, QSizePolicy::Ignored);
    imageLabel->setScaledContents(true);
 
    scrollArea = new QScrollArea;
    scrollArea->setBackgroundRole(QPalette::Dark);
    scrollArea->setWidget(imageLabel);
    setCentralWidget(scrollArea);
    statusBar()->addWidget(ui->frame, 9);
    statusBar()->addWidget(ui->spinBoxZoom, 1);
    ui->frame->setFocus();
    //ui->mainToolBar->setStyleSheet("QToolBar{background-color: rgb(60,60,60);}");
    ui->mainToolBar->setBackgroundRole(QPalette::Window);
}

Re: Image processing error

I noticed now that the back trace you posted is missing two first frames. Can you post the complete backtrace?

Re: Image processing error

Yes, missing 2 first frames. That time I only post backtrace for 4 breakpoints. Now, I edited source code, I have to back to previous code to have full backtrace.
I want to ask that how to invoke brightness processing when slider value changed in Dialog.

Re: Image processing error

I don't need your breakpoints. When the program crashes, print the backtrace from the debugger and post it here.

Re: Image processing error

backtrace it's below.

Code:

Thread 10 (Thread 0x7fffdf131700 (LWP 3430)):
#0  0x00007ffff5de105e in pthread_cond_timedwait@@GLIBC_2.3.2 () from /lib/x86_64-linux-gnu/libpthread.so.0
No symbol table info available.
#1  0x00007ffff5912935 in g_cond_wait_until () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
No symbol table info available.
#2  0x00007ffff58a8b81 in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
No symbol table info available.
#3  0x00007ffff58a91ca in g_async_queue_timeout_pop () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
No symbol table info available.
#4  0x00007ffff58f76b2 in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
No symbol table info available.
#5  0x00007ffff58f6eb5 in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
No symbol table info available.
#6  0x00007ffff5ddcf8e in start_thread () from /lib/x86_64-linux-gnu/libpthread.so.0
No symbol table info available.
#7  0x00007ffff60ebe1d in clone () from /lib/x86_64-linux-gnu/libc.so.6
No symbol table info available.
 
Thread 6 (Thread 0x7fffca449700 (LWP 3426)):
#0  0x00007ffff58cfbb0 in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
No symbol table info available.
#1  0x00007ffff58d3088 in g_main_context_dispatch () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
No symbol table info available.
#2  0x00007ffff58d3248 in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
No symbol table info available.
#3  0x00007ffff58d3304 in g_main_context_iteration () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
No symbol table info available.
#4  0x00007ffff58d3361 in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
No symbol table info available.
#5  0x00007ffff58f6eb5 in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
No symbol table info available.
#6  0x00007ffff5ddcf8e in start_thread () from /lib/x86_64-linux-gnu/libpthread.so.0
No symbol table info available.
#7  0x00007ffff60ebe1d in clone () from /lib/x86_64-linux-gnu/libc.so.6
No symbol table info available.
 
Thread 4 (Thread 0x7fffde930700 (LWP 3423)):
#0  0x00007ffff60df3cd in poll () from /lib/x86_64-linux-gnu/libc.so.6
No symbol table info available.
#1  0x00007ffff58d31dc in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
No symbol table info available.
#2  0x00007ffff58d36ba in g_main_loop_run () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
No symbol table info available.
#3  0x00007fffec8ee4f6 in ?? () from /usr/lib/x86_64-linux-gnu/libgio-2.0.so.0
No symbol table info available.
#4  0x00007ffff58f6eb5 in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
No symbol table info available.
#5  0x00007ffff5ddcf8e in start_thread () from /lib/x86_64-linux-gnu/libpthread.so.0
No symbol table info available.
#6  0x00007ffff60ebe1d in clone () from /lib/x86_64-linux-gnu/libc.so.6
No symbol table info available.
 
Thread 2 (Thread 0x7fffef2d8700 (LWP 3421)):
#0  0x00007ffff60df3cd in poll () from /lib/x86_64-linux-gnu/libc.so.6
No symbol table info available.
#1  0x00007ffff3be4982 in ?? () from /usr/lib/x86_64-linux-gnu/libxcb.so.1
No symbol table info available.
#2  0x00007ffff3be60ff in xcb_wait_for_event () from /usr/lib/x86_64-linux-gnu/libxcb.so.1
No symbol table info available.
#3  0x00007ffff02e7659 in ?? () from /media/bachkimfly/data1/programs/Qt/5.1.1/gcc_64/plugins/platforms/libqxcb.so
No symbol table info available.
#4  0x00007ffff6963eb5 in ?? () from /media/bachkimfly/data1/programs/Qt/5.1.1/gcc_64/lib/libQt5Core.so.5
No symbol table info available.
#5  0x00007ffff5ddcf8e in start_thread () from /lib/x86_64-linux-gnu/libpthread.so.0
No symbol table info available.
#6  0x00007ffff60ebe1d in clone () from /lib/x86_64-linux-gnu/libc.so.6
No symbol table info available.
 
Thread 1 (Thread 0x7ffff7fc9780 (LWP 3417)):
#0  0x00007ffff7087860 in QPixmap::isNull() const () from /media/bachkimfly/data1/programs/Qt/5.1.1/gcc_64/lib/libQt5Gui.so.5
No symbol table info available.
#1  0x00007ffff708789c in QPixmap::toImage() const () from /media/bachkimfly/data1/programs/Qt/5.1.1/gcc_64/lib/libQt5Gui.so.5
No symbol table info available.
#2  0x0000000000406a28 in MainWindow::brightnessProcessing (this=0x7fffffffafc0, value=2) at ../../qt workspace/Auroras/mainwindow.cpp:160
        image = <incomplete type>
        w = 32767
        c = {cspec = 11302176, ct = {argb = {alpha = 0, red = 0, green = 50021, blue = 63345, pad = 32767}, ahsv = {alpha = 0, hue = 0, saturation = 50021, value = 63345, pad = 32767}, acmyk = {alpha = 0, cyan = 0, magenta = 50021, yellow = 63345, black = 32767}, ahsl = {alpha = 0, hue = 0, saturation = 50021, lightness = 63345, pad = 32767}, array = {0, 0, 50021, 63345, 32767}}}
        g = 11302240
        h = 11302176
        r = 0
        b = 0
#3  0x00000000004096e3 in BrightnessContrast::on_horizontalSliderBrightness_valueChanged (this=0x7fffffffc860, value=2) at ../../qt workspace/Auroras/brightnesscontrast.cpp:21
        respond = {<QMainWindow> = {<No data fields>}, static staticMetaObject = {d = {superdata = 0x7ffff7db1760 <QMainWindow::staticMetaObject>, stringdata = 0x428f60 <qt_meta_stringdata_MainWindow>, data = 0x4292a0 <qt_meta_data_MainWindow>, static_metacall = 0x40a2b0 <MainWindow::qt_static_metacall(QObject*, QMetaObject::Call, int, void**)>, relatedMetaObjects = 0x0, extradata = 0x0}}, ui = 0x918080, image = 0x0, imageLabel = 0xc3f1e0, scrollArea = 0xc3f050, scrollBar = 0x7fffffffc860, scaleFactor = 6.9533558068310629e-310}
#4  0x000000000040a591 in BrightnessContrast::qt_static_metacall (_o=0x7fffffffc860, _c=QMetaObject::InvokeMetaMethod, _id=0, _a=0x7fffffffb220) at moc_brightnesscontrast.cpp:73
        _t = 0x7fffffffc860
#5  0x000000000040a6a6 in BrightnessContrast::qt_metacall (this=0x7fffffffc860, _c=QMetaObject::InvokeMetaMethod, _id=0, _a=0x7fffffffb220) at moc_brightnesscontrast.cpp:106
No locals.
#6  0x00007ffff6b54683 in QMetaObject::activate(QObject*, int, int, void**) () from /media/bachkimfly/data1/programs/Qt/5.1.1/gcc_64/lib/libQt5Core.so.5
No symbol table info available.
#7  0x00007ffff7a76e4e in QAbstractSlider::valueChanged(int) () from /media/bachkimfly/data1/programs/Qt/5.1.1/gcc_64/lib/libQt5Widgets.so.5
No symbol table info available.
#8  0x00007ffff77efa8a in QAbstractSlider::setValue(int) () from /media/bachkimfly/data1/programs/Qt/5.1.1/gcc_64/lib/libQt5Widgets.so.5
No symbol table info available.
#9  0x00007ffff7880138 in QSlider::mouseMoveEvent(QMouseEvent*) () from /media/bachkimfly/data1/programs/Qt/5.1.1/gcc_64/lib/libQt5Widgets.so.5
No symbol table info available.
#10 0x00007ffff77278a2 in QWidget::event(QEvent*) () from /media/bachkimfly/data1/programs/Qt/5.1.1/gcc_64/lib/libQt5Widgets.so.5
No symbol table info available.
#11 0x00007ffff787f990 in QSlider::event(QEvent*) () from /media/bachkimfly/data1/programs/Qt/5.1.1/gcc_64/lib/libQt5Widgets.so.5
No symbol table info available.
#12 0x00007ffff76f0b54 in QApplicationPrivate::notify_helper(QObject*, QEvent*) () from /media/bachkimfly/data1/programs/Qt/5.1.1/gcc_64/lib/libQt5Widgets.so.5
No symbol table info available.
#13 0x00007ffff76f3e39 in QApplication::notify(QObject*, QEvent*) () from /media/bachkimfly/data1/programs/Qt/5.1.1/gcc_64/lib/libQt5Widgets.so.5
No symbol table info available.
#14 0x00007ffff6b2cdd4 in QCoreApplication::notifyInternal(QObject*, QEvent*) () from /media/bachkimfly/data1/programs/Qt/5.1.1/gcc_64/lib/libQt5Core.so.5
No symbol table info available.
#15 0x00007ffff76f2fa8 in QApplicationPrivate::sendMouseEvent(QWidget*, QMouseEvent*, QWidget*, QWidget*, QWidget**, QPointer<QWidget>&, bool) () from /media/bachkimfly/data1/programs/Qt/5.1.1/gcc_64/lib/libQt5Widgets.so.5
No symbol table info available.
#16 0x00007ffff7746865 in ?? () from /media/bachkimfly/data1/programs/Qt/5.1.1/gcc_64/lib/libQt5Widgets.so.5
No symbol table info available.
#17 0x00007ffff7748a70 in ?? () from /media/bachkimfly/data1/programs/Qt/5.1.1/gcc_64/lib/libQt5Widgets.so.5
No symbol table info available.
#18 0x00007ffff76f0b54 in QApplicationPrivate::notify_helper(QObject*, QEvent*) () from /media/bachkimfly/data1/programs/Qt/5.1.1/gcc_64/lib/libQt5Widgets.so.5
No symbol table info available.
#19 0x00007ffff76f3fe6 in QApplication::notify(QObject*, QEvent*) () from /media/bachkimfly/data1/programs/Qt/5.1.1/gcc_64/lib/libQt5Widgets.so.5
No symbol table info available.
#20 0x00007ffff6b2cdd4 in QCoreApplication::notifyInternal(QObject*, QEvent*) () from /media/bachkimfly/data1/programs/Qt/5.1.1/gcc_64/lib/libQt5Core.so.5
No symbol table info available.
...............................................

and next:

Code:

......................................................
#21 0x00007ffff703801b in QGuiApplicationPrivate::processMouseEvent(QWindowSystemInterfacePrivate::MouseEvent*) () from /media/bachkimfly/data1/programs/Qt/5.1.1/gcc_64/lib/libQt5Gui.so.5
No symbol table info available.
#22 0x00007ffff70388ed in QGuiApplicationPrivate::processWindowSystemEvent(QWindowSystemInterfacePrivate::WindowSystemEvent*) () from /media/bachkimfly/data1/programs/Qt/5.1.1/gcc_64/lib/libQt5Gui.so.5
No symbol table info available.
#23 0x00007ffff7021a98 in QWindowSystemInterface::sendWindowSystemEventsImplementation(QFlags<QEventLoop::ProcessEventsFlag>) () from /media/bachkimfly/data1/programs/Qt/5.1.1/gcc_64/lib/libQt5Gui.so.5
No symbol table info available.
#24 0x00007ffff033b940 in ?? () from /media/bachkimfly/data1/programs/Qt/5.1.1/gcc_64/plugins/platforms/libqxcb.so
No symbol table info available.
#25 0x00007ffff58d2f05 in g_main_context_dispatch () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
No symbol table info available.
#26 0x00007ffff58d3248 in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
No symbol table info available.
#27 0x00007ffff58d3304 in g_main_context_iteration () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
No symbol table info available.
#28 0x00007ffff6b77314 in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from /media/bachkimfly/data1/programs/Qt/5.1.1/gcc_64/lib/libQt5Core.so.5
No symbol table info available.
#29 0x00007ffff6b2bb6b in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () from /media/bachkimfly/data1/programs/Qt/5.1.1/gcc_64/lib/libQt5Core.so.5
No symbol table info available.
#30 0x00007ffff78e446d in QDialog::exec() () from /media/bachkimfly/data1/programs/Qt/5.1.1/gcc_64/lib/libQt5Widgets.so.5
No symbol table info available.
#31 0x00000000004066fe in MainWindow::on_actionBrightness_Contrast_triggered (this=0x7fffffffe210) at ../../qt workspace/Auroras/mainwindow.cpp:103
        w = {<QDialog> = {<No data fields>}, static staticMetaObject = {d = {superdata = 0x7ffff7da00c0 <QDialog::staticMetaObject>, stringdata = 0x4294c0 <qt_meta_stringdata_BrightnessContrast>, data = 0x4295c0 <qt_meta_data_BrightnessContrast>, static_metacall = 0x40a544 <BrightnessContrast::qt_static_metacall(QObject*, QMetaObject::Call, int, void**)>, relatedMetaObjects = 0x0, extradata = 0x0}}, ui = 0x9f18e0}
#32 0x000000000040a3bb in MainWindow::qt_static_metacall (_o=0x7fffffffe210, _c=QMetaObject::InvokeMetaMethod, _id=11, _a=0x7fffffffcaa0) at moc_mainwindow.cpp:133
        _t = 0x7fffffffe210
#33 0x000000000040a4dc in MainWindow::qt_metacall (this=0x7fffffffe210, _c=QMetaObject::InvokeMetaMethod, _id=11, _a=0x7fffffffcaa0) at moc_mainwindow.cpp:169
No locals.
#34 0x00007ffff6b54683 in QMetaObject::activate(QObject*, int, int, void**) () from /media/bachkimfly/data1/programs/Qt/5.1.1/gcc_64/lib/libQt5Core.so.5
No symbol table info available.
#35 0x00007ffff76e5ba2 in QAction::triggered(bool) () from /media/bachkimfly/data1/programs/Qt/5.1.1/gcc_64/lib/libQt5Widgets.so.5
No symbol table info available.
#36 0x00007ffff76e79d7 in QAction::activate(QAction::ActionEvent) () from /media/bachkimfly/data1/programs/Qt/5.1.1/gcc_64/lib/libQt5Widgets.so.5
No symbol table info available.
#37 0x00007ffff786620a in ?? () from /media/bachkimfly/data1/programs/Qt/5.1.1/gcc_64/lib/libQt5Widgets.so.5
No symbol table info available.
#38 0x00007ffff786d41f in ?? () from /media/bachkimfly/data1/programs/Qt/5.1.1/gcc_64/lib/libQt5Widgets.so.5
No symbol table info available.
#39 0x00007ffff786e3a0 in QMenu::mouseReleaseEvent(QMouseEvent*) () from /media/bachkimfly/data1/programs/Qt/5.1.1/gcc_64/lib/libQt5Widgets.so.5
No symbol table info available.
#40 0x00007ffff772786e in QWidget::event(QEvent*) () from /media/bachkimfly/data1/programs/Qt/5.1.1/gcc_64/lib/libQt5Widgets.so.5
No symbol table info available.
#41 0x00007ffff78700eb in QMenu::event(QEvent*) () from /media/bachkimfly/data1/programs/Qt/5.1.1/gcc_64/lib/libQt5Widgets.so.5
No symbol table info available.
#42 0x00007ffff76f0b54 in QApplicationPrivate::notify_helper(QObject*, QEvent*) () from /media/bachkimfly/data1/programs/Qt/5.1.1/gcc_64/lib/libQt5Widgets.so.5
No symbol table info available.
#43 0x00007ffff76f3e39 in QApplication::notify(QObject*, QEvent*) () from /media/bachkimfly/data1/programs/Qt/5.1.1/gcc_64/lib/libQt5Widgets.so.5
No symbol table info available.
#44 0x00007ffff6b2cdd4 in QCoreApplication::notifyInternal(QObject*, QEvent*) () from /media/bachkimfly/data1/programs/Qt/5.1.1/gcc_64/lib/libQt5Core.so.5
No symbol table info available.
#45 0x00007ffff76f2fa8 in QApplicationPrivate::sendMouseEvent(QWidget*, QMouseEvent*, QWidget*, QWidget*, QWidget**, QPointer<QWidget>&, bool) () from /media/bachkimfly/data1/programs/Qt/5.1.1/gcc_64/lib/libQt5Widgets.so.5
No symbol table info available.
#46 0x00007ffff774656c in ?? () from /media/bachkimfly/data1/programs/Qt/5.1.1/gcc_64/lib/libQt5Widgets.so.5
No symbol table info available.
#47 0x00007ffff7748a70 in ?? () from /media/bachkimfly/data1/programs/Qt/5.1.1/gcc_64/lib/libQt5Widgets.so.5
No symbol table info available.
#48 0x00007ffff76f0b54 in QApplicationPrivate::notify_helper(QObject*, QEvent*) () from /media/bachkimfly/data1/programs/Qt/5.1.1/gcc_64/lib/libQt5Widgets.so.5
No symbol table info available.
#49 0x00007ffff76f3fe6 in QApplication::notify(QObject*, QEvent*) () from /media/bachkimfly/data1/programs/Qt/5.1.1/gcc_64/lib/libQt5Widgets.so.5
No symbol table info available.
#50 0x00007ffff6b2cdd4 in QCoreApplication::notifyInternal(QObject*, QEvent*) () from /media/bachkimfly/data1/programs/Qt/5.1.1/gcc_64/lib/libQt5Core.so.5
No symbol table info available.
#51 0x00007ffff703801b in QGuiApplicationPrivate::processMouseEvent(QWindowSystemInterfacePrivate::MouseEvent*) () from /media/bachkimfly/data1/programs/Qt/5.1.1/gcc_64/lib/libQt5Gui.so.5
No symbol table info available.
#52 0x00007ffff70388ed in QGuiApplicationPrivate::processWindowSystemEvent(QWindowSystemInterfacePrivate::WindowSystemEvent*) () from /media/bachkimfly/data1/programs/Qt/5.1.1/gcc_64/lib/libQt5Gui.so.5
No symbol table info available.
#53 0x00007ffff7021a98 in QWindowSystemInterface::sendWindowSystemEventsImplementation(QFlags<QEventLoop::ProcessEventsFlag>) () from /media/bachkimfly/data1/programs/Qt/5.1.1/gcc_64/lib/libQt5Gui.so.5
No symbol table info available.
#54 0x00007ffff033b940 in ?? () from /media/bachkimfly/data1/programs/Qt/5.1.1/gcc_64/plugins/platforms/libqxcb.so
No symbol table info available.
#55 0x00007ffff58d2f05 in g_main_context_dispatch () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
No symbol table info available.
#56 0x00007ffff58d3248 in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
No symbol table info available.
#57 0x00007ffff58d3304 in g_main_context_iteration () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
No symbol table info available.
#58 0x00007ffff6b77314 in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from /media/bachkimfly/data1/programs/Qt/5.1.1/gcc_64/lib/libQt5Core.so.5
No symbol table info available.
#59 0x00007ffff6b2bb6b in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () from /media/bachkimfly/data1/programs/Qt/5.1.1/gcc_64/lib/libQt5Core.so.5
No symbol table info available.
#60 0x00007ffff6b2fbbe in QCoreApplication::exec() () from /media/bachkimfly/data1/programs/Qt/5.1.1/gcc_64/lib/libQt5Core.so.5
No symbol table info available.
#61 0x0000000000405aa6 in main (argc=1, argv=0x7fffffffe368) at ../../qt workspace/Auroras/main.cpp:10
        a = <incomplete type>
        w = {<QMainWindow> = {<No data fields>}, static staticMetaObject = {d = {superdata = 0x7ffff7db1760 <QMainWindow::staticMetaObject>, stringdata = 0x428f60 <qt_meta_stringdata_MainWindow>, data = 0x4292a0 <qt_meta_data_MainWindow>, static_metacall = 0x40a2b0 <MainWindow::qt_static_metacall(QObject*, QMetaObject::Call, int, void**)>, relatedMetaObjects = 0x0, extradata = 0x0}}, ui = 0x947290, image = 0xabaf80, imageLabel = 0x9955d0, scrollArea = 0x951f60, scrollBar = 0x40a6d0 <__libc_csu_init>, scaleFactor = 1}

Re: Image processing error

Do you have two threads accessing your UI?

Re: Image processing error

Quote:

Originally Posted by wysota

Do you have two threads accessing your UI?

what do that mean?

Added after 1 12 minutes:

I know that calling a mainwindow's function from a dialog is a bad practice. So, I found out a instruction:

Quote:

You should emit a signal acknowledging that the user has made an input, and connect that signal to a proper slot in your MainWindow and connect that signal and slot in your MainWindow's constructor

But i don't perform to this way. Can you help me by some example?

Added after 33 minutes:

I did this, but nothing change. what did I wrong?
Code:

//brightnesscontrast.cpp MainWindow respond; connect(ui->horizontalSliderBrightness, SIGNAL(valueChanged(int)), &respond, SLOT(respond.brightnessProcessing(value);));

Re: Image processing error

Quote:

Originally Posted by bachkimfly

what do that mean?

I don't know how to make that clearer. Are you starting any threads in your program?

Quote:

But i don't perform to this way. Can you help me by some example?

I'm afraid "some example" will not help you, there are already a lot of examples on using signals and slots so making one more would not change anything.
Quote:
I did this, but nothing change. what did I wrong?
Code:

//brightnesscontrast.cpp MainWindow respond; connect(ui->horizontalSliderBrightness, SIGNAL(valueChanged(int)), &respond, SLOT(respond.brightnessProcessing(value);));
respond goes out of scope and is destroyed before it has a chance to do anything. I think you need to improve your C++ skills, especially the concept of pointers, variable scopes and such.

Re: Image processing error

yep. thank for helping

1 Attachment(s)

Re: Image processing error

Hi bachkimfly,
You need to learn more about signals and slots.
I give you simple code using your problems.
I hope you can get more information about implement signal and slots from this example.
Please running the program, click setting toolbar and try to change slider brightness.

Thank you.
Best regards,

Myta