How to prevent the mouse click event from happening when the button is Disabled

[Pradeep P N]

@J.Hilk
i am bit confused with the statement in fact.

"but while i click the button when it is disabled after enabling the button the click signal gets emitted and the click function is executed"

• i click the button when it is disabled -> Nothing will work as Button is Disabled.
• after enabling the button the click signal gets emitted -> Yes as after 3s timer the button is enabled and can be clicked.

[J.Hilk]

@Pradeep-P-N

What I get out of @ManiRon statement is:

• Button is disabled
• Button gets pressed/clicked
• • nothing happens, as expected
• Button gets set to enabled
• • clicked signal is emitted without button interaction

Thats not normal behavior in my opinion

I'll make a quick test case

@ManiRon what Qt Version what OS btw?

[Pradeep P N]

Hmmm, Got it @J-Hilk
Thanks.

@ManiRon Can you share a sample code ?
You said you are using the QTimer.
Just wanted to check if there is anything mismatch with the code.

[J.Hilk]

@J.Hilk said in How to prevent the mouse click event from happening when the button is Disabled:

If true, then that's a bug in the library!

Nope, not true 5.12.4 MacOS, no unexpected clicked emits

int main(int argc, char *argv[])
{

    QApplication a(argc, argv);

    auto *btn = new QPushButton("Enabled");
    btn->resize(200, 50);
    btn->show();

    QObject::connect(btn, &QPushButton::clicked, [btn]()->void{
                         btn->setEnabled(false);
                         btn->setText("Disabled");
                         qDebug("Btn clicked");
                     });
    QObject::connect(btn, &QPushButton::pressed, []()->void{qDebug("Btn Pressed"); });
    QObject::connect(btn, &QPushButton::released, []()->void{qDebug("Btn Released"); });

    QTimer t_reset;
    t_reset.setInterval(3000);
    QObject::connect(&t_reset, &QTimer::timeout, btn, [btn]()->void{btn->setEnabled(true); btn->setText("Enabled");});

    QObject::connect(btn, &QPushButton::clicked, &t_reset, QOverload<>::of(&QTimer::start));

    return  a.exec();
}

[Pradeep P N]

@J-Hilk
Even i tried on 5.12.3 - Ubuntu 16.04 & the above code ( From my post ).
Also the one shared by you.
It works fine.

• No Click called related to button enable/disable status.

[jsulm]

@ManiRon Please add

qDebug() << ui->pushButton->enabled();

to your slot and see what it outputs when you click on the button while it is disabled.
And please debug you app more carefully: you say you have a timeout to activate the button again (you should have said that in your first post already)? Did you make sure the button was not yet activated? Is it the same if you disable you style sheet?

[ManiRon]

@J.Hilk QT 5.5.0 QT Creator version 3.4.2 OS Windows Vista

[ManiRon]

@jsulm Yes i made sure cause i enable the button after 3s only , and this statement is not there , it throws error (qDebug() << ui->pushButton->enabled())

[Pradeep P N]

@ManiRon
Did you add #include <QDebug>

Ad if so -> What is the error ?

[ManiRon]

@Pradeep-P-N yes

[ManiRon]

@Pradeep-P-N

class QPushButton' has no member named 'enabled'
qDebug() << ui->pushbutton->enabled();
^

[Pradeep P N]

@ManiRon

Use qDebug() << ui->pushButton->isEnabled();

You cannot do ui->pushButton->enabled()

• Refer enabled.

Access functions:

• bool isEnabled() const
• void setEnabled(bool)

[ManiRon]

@Pradeep-P-N

After the button gets enabled the signal automatically called based on my previous click

and the print came as

Inside Pushbutton
ui->Pushbutton->isEnabled() 1
Inside Pushbutton
ui->Pushbutton->isEnabled() 1
Inside Pushbutton
ui->Pushbutton->isEnabled() 1

[Pradeep P N]

@ManiRon You dint debug the code after you disabled right ?

• From your log i can clearly see that your PushButton was never disabled.

    ui->pushButton->setEnabled(false);

    qDebug() << ui->pushButton->isEnabled();

[ManiRon]

@Pradeep-P-N

Print was done before disabling
Now done after disable
Inside Pushbutton
ui->Pushbutton->isEnabled() 0
Inside Pushbutton
ui->Pushbutton->isEnabled() 0

[Pradeep P N]

Hi @ManiRon

• Please don't hurry, and just don't copy paste the code from the posts.
• Adding proper debug() messages will help us to understand the code flow and resolve the issue. @jsulm @J-Hilk (Correct me if wrong)
• Here the thing is to debug the flow and code.
• We should check the flow of the code with respect to issue.
  • Button is disabled.
  • Button clicked.
  • Button gets set to enabled after few seconds.
  • clicked signal is emitted without button interaction.

All the best.

[ManiRon]

@Pradeep-P-N ya this is the sequence

[Pradeep P N]

@ManiRon
Ok, Please add some debug messages for the flow in your code so we can get it clearly.

Just Adding qDebug() << ui->Pushbutton->isEnabled() ; will not provide us the details of the flow to resolve the error.

[koprok]

@ManiRon , @Pradeep-P-N , do you have something new regarding this issue? Did you solve it?
I have a similar one, i.e. when clicking on a disabled QPushButton, clicked() signal is emitted once the button gets enabled. My Qt version is 5.9.4 running on Linux.

[Daniil 0]

Hi all, I am using Qt5.12.3 and have the same problem as @ManiRon and @koprok. (@koprok, read this post carefully you will find the solution to the problem but i think it is still the problem in the library!) For the following code:
main.h:

#include <QMainWindow>
#include <QObject>

class QPushButton;
class QProgressBar;

class mainWindow : public QMainWindow
{
  Q_OBJECT
  
  QPushButton* button;
  QProgressBar* bar;
  
public slots:
  void on_click();

public:
  mainWindow();
};

main.cpp:

#include <QApplication>
#include <QPushButton>
#include <QProgressBar>
#include <QStatusBar>
#include <QThread>
#include <QLayout>
#include "main.h"
#include <iostream>

void mainWindow::on_click()
{
  button->setEnabled(false);
  std::cout << "clicked" << '\n';
  for(int i=0;i<100;i++)
  {
    bar->setValue(i);
    QThread::usleep(30000);
    //QCoreApplication::processEvents();
  }
  button->setEnabled(true);
}
  
mainWindow::mainWindow()
{
  QVBoxLayout* mainLayout = new QVBoxLayout;

  button = new QPushButton("Hello world !");
  connect(button, &QPushButton::clicked, this, &mainWindow::on_click);
  mainLayout->addWidget(button);
  bar = new QProgressBar();
  bar->setRange(0,100);
  bar->setValue(0);
  QStatusBar* sb = new QStatusBar();
  sb->addWidget(bar);
  mainLayout->addWidget(sb);

  setCentralWidget(new QWidget);
  centralWidget()->setLayout(mainLayout);
}

int main(int argc, char **argv)
{
 QApplication app (argc, argv);

 mainWindow obj;
 obj.show();

 return app.exec();
}

I have the following behavior. When I press a button the progress bar starts to fill up the button becomes inactive. Clicking the button while for loop is not finished does not produce anything (nor progress bar restart nor output to std::cout). But it somehow puts events into a queue and and after loop is finished and button became active it proceeds to next click event which look totally odd.
With uncommented processEvents() everything works as expected: while button is inactive (for loop animates the progress) click event does not produce anything and is not stored anywhere, i.e. when button becomes active again nothing happens.
Without setEnabled without processEvents it behaves very similar to first variant except user expects something since button look active.
Without setEnabled but with processEvents it behaves quite odd from user perspective but still okay since every time active button is started it starts new process and then gets to old one from the point where it was interrupted.
I would say only the code presented above as is looks to reveal some real problem in Qt other variants are okay.

P.S. Same thing happens for button in QDialog