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using QKeyEvents

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  • SGaistS SGaist

    Since I don't have the .ui file I modified the code a bit.

    I created a QPushButton and did an explicit connection and it worked was expected.

    mzimmersM Offline
    mzimmersM Offline
    mzimmers
    wrote on last edited by
    #25

    @SGaist well, doesn't that tear the rag right off the bush.

    What exactly did you mean by "explicit" connection?

    1 Reply Last reply
    0
    • SGaistS Offline
      SGaistS Offline
      SGaist
      Lifetime Qt Champion
      wrote on last edited by
      #26

      By explicit I meant writing the connect statement. Currently you are using the connectSlotsByName feature that is called as part of setupUi.

      Interested in AI ? www.idiap.ch
      Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

      1 Reply Last reply
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      • mzimmersM Offline
        mzimmersM Offline
        mzimmers
        wrote on last edited by
        #27

        OK...I added the explicit connection in widget.cpp:

            connect(ui->pushButtonNics, &QPushButton::clicked, this, &Widget::on_pushButtonNics_clicked);
        

        Here's my widget.ui:

        <?xml version="1.0" encoding="UTF-8"?>
        <ui version="4.0">
         <class>Widget</class>
         <widget class="QWidget" name="Widget">
          <property name="geometry">
           <rect>
            <x>0</x>
            <y>0</y>
            <width>320</width>
            <height>160</height>
           </rect>
          </property>
          <property name="sizePolicy">
           <sizepolicy hsizetype="Preferred" vsizetype="MinimumExpanding">
            <horstretch>0</horstretch>
            <verstretch>0</verstretch>
           </sizepolicy>
          </property>
          <property name="minimumSize">
           <size>
            <width>320</width>
            <height>160</height>
           </size>
          </property>
          <property name="windowTitle">
           <string>Discovery Utility</string>
          </property>
          <widget class="QPushButton" name="pushButtonNics">
           <property name="geometry">
            <rect>
             <x>130</x>
             <y>50</y>
             <width>75</width>
             <height>23</height>
            </rect>
           </property>
           <property name="text">
            <string>NICs</string>
           </property>
          </widget>
         </widget>
         <layoutdefault spacing="6" margin="11"/>
         <resources/>
         <connections/>
        </ui>
        

        And, just for good measure, here's main.cpp:

        #include <QApplication>
        
        #include <stdio.h>
        
        #include "widget.h"
        
        using namespace std;
        
        int main(int argc, char *argv[])
        {
            int rc;
            QApplication a(argc, argv);
            Widget *widget;
        
            widget = new Widget();
            widget->show();
            rc = a.exec();
            return rc;
        }
        

        This is my entire project, except for the pro file itself:

        QT       += core gui network serialport xml
        
        greaterThan(QT_MAJOR_VERSION, 4): QT += widgets
        
        TARGET = discovery_utility_test
        DEFINES += QT_DEPRECATED_WARNINGS
        SOURCES += \
        	keypress.cpp \
        	main.cpp \
        	nics.cpp \
        	widget.cpp
        
        HEADERS += \
        	keypress.h \
        	nics.h \
        	widget.h \
        
        FORMS += \
        	nics.ui \
        	widget.ui
        

        Could it possibly be due to the way that I'm building it? Or, maybe a Windows issue (you're testing on Linux, right)?

        Thanks...

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        • mzimmersM Offline
          mzimmersM Offline
          mzimmers
          wrote on last edited by
          #28

          This problem has to do with setting the button's visibility. If I disable this line in my widget c'tor:

          //    ui->pushButtonNics->setVisible(false);
          

          My slot receives the signal, and opens the Nics dialog. After the dialog closes, I set the button to not visible, and the problem recurs.

          This problem exists on Windows 10, but not on MacOS. Could it be a bug?

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          • SGaistS Offline
            SGaistS Offline
            SGaist
            Lifetime Qt Champion
            wrote on last edited by
            #29

            One silly test, did you try to make the button invisible after calling connect. AFAIK, it should have no relation but it's worth a shot.

            Interested in AI ? www.idiap.ch
            Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

            mzimmersM 1 Reply Last reply
            0
            • SGaistS SGaist

              One silly test, did you try to make the button invisible after calling connect. AFAIK, it should have no relation but it's worth a shot.

              mzimmersM Offline
              mzimmersM Offline
              mzimmers
              wrote on last edited by
              #30

              @SGaist yes, that's how I had it:

              Widget::Widget(QWidget *parent) :
                  QWidget(parent),
                  ui(new Ui::Widget)
              {
                  ui->setupUi(this);
              
                  // create and connect a KeyPress object.
                  m_keyPress = new KeyPress(this);
                  connect(m_keyPress, &KeyPress::keyEvent, this, &Widget::handleKeyEvent);
                  connect(ui->pushButtonNics, &QPushButton::clicked, this, &Widget::on_pushButtonNics_clicked);
                  installEventFilter(m_keyPress);
              
                  // hide the button for the NICs window.
              //    ui->pushButtonNics->setVisible(false);
              }
              
              1 Reply Last reply
              0
              • mzimmersM Offline
                mzimmersM Offline
                mzimmers
                wrote on last edited by
                #31

                Update: I submitted a bug report on this; no movement on it yet.

                One of my users noticed that the application is now rather CPU-intensive. I verified that it was the key filter by disabling this code in my main widget:

                    m_keyPress = new KeyPress(this);
                    connect(m_keyPress, &KeyPress::keyEvent, this, &Widget::handleKeyEvent);
                    installEventFilter(m_keyPress);
                

                Here's the filter:

                bool KeyPress::eventFilter(QObject *obj, QEvent *ev)
                {
                    Q_UNUSED(obj)
                
                    bool rc = false;
                    int key;
                    QKeyEvent *qke;
                    QEvent::Type type = ev->type();
                    if (type == QEvent::ShortcutOverride || type == QEvent::KeyRelease)
                    {
                        qke = static_cast<QKeyEvent *>(ev);
                        key = qke->key();
                
                        // don't bother signaling when the key isn't meaningful to us.
                        if (key == 'c' || key == 'C' || key == 'd' || key == 'D')
                        {
                            emit keyEvent(*ev, key);
                        }
                        rc = true;
                    }
                    else
                    {
                        rc = QObject::eventFilter(obj, ev);
                    }
                    return rc;
                }
                

                I don't see anything really inefficient in my code, but with this enabled, the app uses ~15% of my CPU (on an i3) at idle. Is this to be expected, or am I doing something wrong?

                Thanks...

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                • SGaistS Offline
                  SGaistS Offline
                  SGaist
                  Lifetime Qt Champion
                  wrote on last edited by
                  #32

                  What type of widgets are you checking ?
                  You can add an additional check for the obj parameter class to avoid further checks.

                  Interested in AI ? www.idiap.ch
                  Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

                  JonBJ mzimmersM 2 Replies Last reply
                  0
                  • SGaistS SGaist

                    What type of widgets are you checking ?
                    You can add an additional check for the obj parameter class to avoid further checks.

                    JonBJ Offline
                    JonBJ Offline
                    JonB
                    wrote on last edited by
                    #33

                    @SGaist
                    If @mzimmers says:

                    but with this enabled, the app uses ~15% of my CPU (on an i3) at idle

                    assuming "idle" means not pressing any key, why is this KeyPress::eventFilter() being hit at all, let alone loads of times to use that CPU?

                    mzimmersM 1 Reply Last reply
                    0
                    • SGaistS SGaist

                      What type of widgets are you checking ?
                      You can add an additional check for the obj parameter class to avoid further checks.

                      mzimmersM Offline
                      mzimmersM Offline
                      mzimmers
                      wrote on last edited by
                      #34

                      @SGaist well, maybe that's my problem -- I'm checking the entire QWidget. (The idea was to reveal hidden buttons when certain keys were pressed.) Given that, I'm not sure there's any meaningful obj parameter checking I can do.

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                      0
                      • JonBJ JonB

                        @SGaist
                        If @mzimmers says:

                        but with this enabled, the app uses ~15% of my CPU (on an i3) at idle

                        assuming "idle" means not pressing any key, why is this KeyPress::eventFilter() being hit at all, let alone loads of times to use that CPU?

                        mzimmersM Offline
                        mzimmersM Offline
                        mzimmers
                        wrote on last edited by
                        #35

                        @JonB I suspect I'm doing something wrong with my use of the filter, but I'm not sure what to change. I think my filterEvent() is being called for all events, not just for key events.

                        JonBJ 1 Reply Last reply
                        0
                        • mzimmersM mzimmers

                          @JonB I suspect I'm doing something wrong with my use of the filter, but I'm not sure what to change. I think my filterEvent() is being called for all events, not just for key events.

                          JonBJ Offline
                          JonBJ Offline
                          JonB
                          wrote on last edited by
                          #36

                          @mzimmers said in using QKeyEvents:

                          I think my filterEvent() is being called for all events, not just for key events.

                          I suspect that is more like it ;-) I would worry about that before anything else :)

                          Use a debugger or qDebug()s to at least see when your filter is being hit, when the user isn't doing anything?

                          mzimmersM 1 Reply Last reply
                          0
                          • JonBJ JonB

                            @mzimmers said in using QKeyEvents:

                            I think my filterEvent() is being called for all events, not just for key events.

                            I suspect that is more like it ;-) I would worry about that before anything else :)

                            Use a debugger or qDebug()s to at least see when your filter is being hit, when the user isn't doing anything?

                            mzimmersM Offline
                            mzimmersM Offline
                            mzimmers
                            wrote on last edited by
                            #37

                            @JonB

                                qDebug() << QTime::currentTime().toString();
                            

                            Got about 6000 hits in ~2 seconds of run time. That explains the CPU usage.

                            I have no idea what could possibly be generating that many events, though.

                            JonBJ 1 Reply Last reply
                            0
                            • mzimmersM mzimmers

                              @JonB

                                  qDebug() << QTime::currentTime().toString();
                              

                              Got about 6000 hits in ~2 seconds of run time. That explains the CPU usage.

                              I have no idea what could possibly be generating that many events, though.

                              JonBJ Offline
                              JonBJ Offline
                              JonB
                              wrote on last edited by
                              #38

                              @mzimmers
                              Start by debugging out ev->type()!

                              mzimmersM 1 Reply Last reply
                              0
                              • JonBJ JonB

                                @mzimmers
                                Start by debugging out ev->type()!

                                mzimmersM Offline
                                mzimmersM Offline
                                mzimmers
                                wrote on last edited by mzimmers
                                #39

                                @JonB the great majority were:

                                QEvent::UpdateRequest
                                QEvent::Paint

                                UPDATE: I managed to eliminate the flood of events, but...that didn't have an effect on my CPU usage. The problem is definitely in the KeyEvent class -- when I comment it out, CPU usage is nil. Anyone have any ideas?

                                1 Reply Last reply
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                                • mzimmersM Offline
                                  mzimmersM Offline
                                  mzimmers
                                  wrote on last edited by
                                  #40

                                  Update on this, documented here

                                  The behaviour is different because clicked is emitted on button down on macOS, but on button up on the other two[Windows and Linux]. While the keyboard keys are down, the QPushButton stays down. That's a UX difference caused by how the OS itself behaves.

                                  So, my idea for using the keys goes out the window...I'll think of something else.

                                  The performance issue is a mystery, but I'm going to open a new thread on that. Thanks to everyone for looking.

                                  1 Reply Last reply
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