QTimer doesn't work the expected way

MasterBlade

Hi I have a save button. I want to make it so that when a user clicks it, it gets disabled immediately and a text saying 'Saved." appears. The text disappears after 750 ms. So I coded it like this.

But after running the program, I found that it actually worked this way.
The program pauses for 750 ms. After that the save button gets disabled and the text blinks for a moment.
What's the problem?

ui->Save->setEnabled(false);
ui->saved->show();
QTimer::singleShot(750, [=](){ui->saved->hide();});

jsulm

@MasterBlade said in QTimer doesn't work the expected way:

The program pauses for 750 ms.

I would say you need to post more of your code. singleShot should not block your app.

MasterBlade

@jsulm said in QTimer doesn't work the expected way:

@MasterBlade said in QTimer doesn't work the expected way:

The program pauses for 750 ms.

I would say you need to post more of your code. singleShot should not block your app.

I think you are correct. I commented all other codes and the program worked as expected.
But I didn't find any problems with those commented codes. I can post them here. They are mainly used to write INI files.

void Database::on_Save_clicked()
{
    if (ui->Numbers->property("no1").toInt() == 0){
        qDebug() << "Trying to Save an Empty Card on_Save_clicked().";
        return;
    }
    QSettings set("*PATH*", QSettings::IniFormat);
    set.beginGroup(ui->Numbers->text());

    set.setValue("no1", ui->Numbers->property("no1"));
    /* All are setValue() */
    set.setValue("Type", ui->Types->text());

    QStringList sublist = ui->Types->property("SubList").toStringList();
    if (sublist.size() < 2){
        set.setValue("SubList", "");
    }
    else{
        set.setValue("SubList", ui->Types->property("SubList"));
    }
    UpdateTypes();

    set.setValue("Cost", ui->cost_value->text());
    /* All are setValue() */
    set.setValue("ResComm", ui->Restrictions->property("Comm").toInt());

    set.endGroup();

    ui->Save->setEnabled(false);
    ui->saved->show();
    QTimer::singleShot(750, [=]{ui->saved->hide();});
}

jsulm

@MasterBlade said in QTimer doesn't work the expected way:

UpdateTypes();

What does this do?

MasterBlade

@jsulm said in QTimer doesn't work the expected way:

@MasterBlade said in QTimer doesn't work the expected way:

UpdateTypes();

What does this do?

It is used to collect some info from the ui and update a QPushButton. I tried to comment it only and The program still got blocked.

MasterBlade

@jsulm said in QTimer doesn't work the expected way:

@MasterBlade said in QTimer doesn't work the expected way:

UpdateTypes();

What does this do?

In case you really need to check this. It looks like this.

void Database::UpdateTypes()
{
    bool IScroll, NScroll;
    /* other bool variables */
    QString str;

    IScroll = ui->Types->property("IScroll").toBool();
    NScroll = ui->Types->property("NScroll").toBool();
    /* other variable assignments */

    if (IScroll) str += tr("IScroll") + " ";
    if (NScroll) str += tr("NScroll") + " ";
    /* OtherCondition Check */
    str.remove(str.size() - 1, 1);

    QStringList Sublist = ui->Types->property("SubList").toStringList();
    int size = Sublist.size() / 2;

    if (size){
        str += " -";
        for (int i = 0; i < size; ++i){
            str += " " + Sublist.at(i * 2);
        }
    }

    if (str.isEmpty()){
        str = tr("Main && Subtypes");
    }
    ui->Types->setText(str);
}

Christian Ehrlicher

Run your program with a debugger, stop the debugger when your program stops and take a look at the backtrace where it comes from.

MasterBlade

@Christian-Ehrlicher said in QTimer doesn't work the expected way:

Run your program with a debugger, stop the debugger when your program stops and take a look at the backtrace where it comes from.

I am currently running the program with QTCreator in debug mode. May I ask how to stop the debugger?

MasterBlade

@Christian-Ehrlicher said in QTimer doesn't work the expected way:

Run your program with a debugger, stop the debugger when your program stops and take a look at the backtrace where it comes from.

Hi I have set the single shot duration to 10 secs and rerun the program. It pauses for 2 secs and the text disappeared at 10 sec.
Does this mean there is a long latency when writing INI? I need to write 40 items to the INI file.

jsulm

@MasterBlade said in QTimer doesn't work the expected way:

May I ask how to stop the debugger?

Simply press the same button you used to start debugging...

MasterBlade

@jsulm said in QTimer doesn't work the expected way:

@MasterBlade said in QTimer doesn't work the expected way:

May I ask how to stop the debugger?

Simply press the same button you used to start debugging...

I paused the debugger, but didn't find many differences. Application output only has a single line. Where else should I check?

15:16:35: Debugging starts

jsulm

@MasterBlade said in QTimer doesn't work the expected way:

Where else should I check?

In the debugger. In debugger view there is "Debugger" section with the stack trace (select thread #1). You should really get familiar with the debugger.

MasterBlade

@jsulm said in QTimer doesn't work the expected way:

@MasterBlade said in QTimer doesn't work the expected way:

Where else should I check?

In the debugger. In debugger view there is "Debugger" section with the stack trace (select thread #1). You should really get familiar with the debugger.

jsulm

@MasterBlade When exactly did you take this screen-shot? When your app was blocked? You also can check other threads.

MasterBlade

@jsulm said in QTimer doesn't work the expected way:

@MasterBlade When exactly did you take this screen-shot? When your app was blocked? You also can check other threads.

Yeah it was taken when the program was blocked.
Thread #1-5 looks the same to me.

Thread #6 and #7

#8 and #9 are same as #1-5

#10-13

#14

#15

jsulm

@MasterBlade Do you actually use threads in your app?

MasterBlade

@jsulm said in QTimer doesn't work the expected way:

@MasterBlade Do you actually use threads in your app?

I don't think I did. I don't know why there are so many threads.

jsulm

@MasterBlade That's normal. I just wanted to know whether you create threads also by yourself. From the stack trace I can't see anything helpful.

MasterBlade

@jsulm said in QTimer doesn't work the expected way:

@MasterBlade That's normal. I just wanted to know whether you create threads also by yourself. From the stack trace I can't see anything helpful.

There is one problem I found curious. I am also using QSettings to write INI files, and I found it quite slow. Usually takes like 2 secs to write. I didn't use QTimer in that code. So I guess if it's QSettings that caused the block.

jsulm

@MasterBlade Where are the settings stored? Is it network drive, local drive, Windows registry?