Set Delay Timer

SGaist

Hi and welcome to devnet,

Can you post the code that is triggering the error ?

jsulm

connect(b,&QPushButton::click(),b->void{

Why did you add () after click?
The correct name of the slot is http://doc.qt.io/qt-5/qabstractbutton.html#clicked, so it must be:

connect(b,&QPushButton::clicked,[b]()->void{
...

J.Hilk

@Yrandom You got a lot of good advise from the others. I'll try to add to that.
If you don't wan't do rewrite your code too much, you can change your fuction to something like this.

void VerschiebeSpiel::buttonClicked(QWidget* _button){
    QPushButton* b = dynamic_cast<QPushButton*>(_button);  
    int index = layout->indexOf(_button);   
    int row, col,ax,bx;
    
    if(index != -1){                                
        layout->getItemPosition(index,&row,&col,&ax,&bx);
    }

    if(b){//check if valid cast
        b->setStyleSheet("background-color:green");
        //Timer + Lambda-function to reset the button after 1000 msec
        QTimer::singleShot(1000,this,[=]{b->setStyleSheet("background-color:red");});
    }
}

SGaist

To both: use qobject_cast when dealing with QObject based classes.

Yrandom

@J.Hilk

thx for this example
it works great.

also just mention: i found out other solution for that

using processevents and currenttime
but i want to unterstand how this part work

QCoreApplication::processEvents( QEventLoop::AllEvents, 100 );

What is the 100(maxtime) mean ? because i just need to process the Event again (Loop all Event) and the current time will increase automatically.
I dont need to put 100 as Parameter and it still work

Thx all for the answer


// Delay time for button color
void ss::delay(int millisecondsToWait )
{
    QTime dieTime = QTime::currentTime().addMSecs( millisecondsToWait );
    while( QTime::currentTime() < dieTime )
    {
        QCoreApplication::processEvents( QEventLoop::AllEvents, 100 );
    }
}

jsulm

@Yrandom said in Set Delay Timer:

QCoreApplication::processEvents

Check documentation http://doc.qt.io/qt-5/qcoreapplication.html#processEvents-1
"Processes pending events for the calling thread for maxtime milliseconds or until there are no more events to process, whichever is shorter."
Keep in mind that your solution isn't nice from design point of view and will consume a lot of CPU power.

VRonin

@Yrandom said in Set Delay Timer:

VerschiebeSpiel.cpp.cc: In member function 'void erschiebeSpiel::buttonClicked(QWidget*)':

That's not where you should put the connect. my code snippet should go just after you create the button (in the constructor?)

while( QTime::currentTime() < dieTime )
{
QCoreApplication::processEvents( QEventLoop::AllEvents, 100 );
}

This is just bad design. you are blocking the main thread and forcing the event loop to kinda keep the UI responsive. Nasty

J.Hilk

@Yrandom

Usually during a while loop, all other tasks are suspendet until the loop or more precisely the function returns. That includes the paint/repaint event that is triggered by setStyleSheet().

QCoreApplication::processEvents() is an uncomely way to tell your app, "That with the function, do whatever else is qued".
The Int value you pass to processEvents is a max value in -I believe -ms, you give other Processes to finish their stuff, after that time your code after the call gets processed again.

a While loop now is calling that every eventloop-cycle

My advice, don't use it, if you have other options.

mpergand

A wait function like this:

void wait(float sec)
{
    QElapsedTimer timer;
    timer.start();

    while(! timer.hasExpired(sec*1000))
        QCoreApplication::processEvents();
}

allows you to simpy do that:

b->setStyleSheet("background-color:green");
wait(0.3);
b->setStyleSheet("background-color:red");

Pretty and clean isn't it ?

J.Hilk

@mpergand said in Set Delay Timer:

while(! timer.hasExpired(sec*1000))
    QCoreApplication::processEvents();

Pretty and clean isn't it ?

No, it's not!

Do not use QCoreApplication::processEvents if you can avoid it!

VRonin

@mpergand said in Set Delay Timer:

Pretty and clean isn't it ?

No it is not. it uses 75% of one of my CPU cores for absolutely nothing

mpergand

@j.hilk Do not use QCoreApplication::processEvents if you can avoid it!

Why ?
Explain any good reason to avoid it.

J.Hilk

@mpergand said in Set Delay Timer:

@j.hilk Do not use QCoreApplication::processEvents if you can avoid it!

Why ?
Explain any good reason to avoid it.

At least used in such a loop->
@VRonin said in Set Delay Timer:

No it is not. it uses 75% of one of my CPU cores for absolutely nothing

Its also contrarian to the event-driven programming approach

mpergand

@VRonin said in Set Delay Timer:

No it is not. it uses 75% of one of my CPU cores for absolutely nothing

For .3 sec not a big deal.
I agree, that it's should by used for short period only (< 1 sec)

The main drawback I know (i use the same principle on MacOS) is that it can leading to some reentrant call in some cases.

VRonin

@mpergand said in Set Delay Timer:

For .3 sec not a big deal.

It is. especially on mobile/embedded hardware. it's just bad design especially when alternatives based of QEventLoop exist (but of course use the async is ALWAYS the best design)

mpergand

@VRonin said in Set Delay Timer:

It is. especially on mobile/embedded hardware. it's just bad design especially when alternatives based of QEventLoop exist (but of course use the async is ALWAYS the best design)

Ok, add a small QThread::sleep should do the job as well.

Please, can you post an example of a wait function with a QEventLoop instead.

VRonin

add a small QThread::sleep should do the job as well

it does not, reason in link below

can you post an example of a wait function with a QEventLoop instead.

https://forum.qt.io/topic/78715/why-my-timer-is-not-emit-timeout-signal

Yrandom

WOW. All the discussion :)
First off all, thx for the answer.
I have one more question to fullfill my Project. I dont want to start new Topic.

I have a class GameKonfiguration
and class MainWindow
and the main()

#include "Konfiguration.h"
#include "MainWindow.h"
    
int main(int argc, char *argv[]) {
    // initialize resources, if needed
    // Q_INIT_RESOURCE(resfile);

    QApplication app(argc, argv);
    
    MainWindow *window = new MainWindow(&app);
    window->show();

    Konfiguration *konfiguration = new Konfiguration(&app,window);
    konfiguration->show();

    return app.exec();
}

in main

Now I make this Programm so far, that when i start, both Windows open and i can Change configuration and the gamefield show and user can Play and actually i can quit the game via configuration. everything fine

Now I want to Combine the menu bar from mainwindow and use the menu bar to open my configuration window.
However the Problem i have is now, i cant include Header a in Header b and Header b in Header a.

// mainwindow Header file
#include "ui_MainWindow.h"
#include <QApplication>
//some Header here

//try
#include "Konfiguration.h"
//-- not work because in Konfiguration.h i already include mainwindow.h in oder to use for the Slot etc


using namespace std;

class MainWindow : public QMainWindow {
   Q_OBJECT
private:
    Ui::MainWindow widget;
    QApplication *app;
    // Try
Konfiguration *confi;
    
public:
    MainWindow(QApplication*);
  //some function
    
signals:
    public slots:
      // function etc ........
       void openConfi();
};

 


// in mainwindow.cpp
// Open Game Configuration
    QObject::connect(widget.SpielKonfiguration,SIGNAL(triggered()),this,SLOT(openConfi()));
    
    // End Game
    QObject::connect(widget.SpielBeenden,SIGNAL(triggered()),app,SLOT(quit()));

 // Configuration Window
void MainWindow::openConfi(){
    // in this Slot , the configuration window should open
confi->show();
}

Konfiguration.h and cpp

#ifndef KONFIGURATION_H
#define KONFIGURATION_H


#include <QApplication>
#include "MainWindow.h"
// some Header here....

class Konfiguration : public QDialog{
    Q_OBJECT
    
private:
    QApplication *app;
  // here i create mainwindow pointer to Setup the gamefield
    MainWindow *spielFenster;    
       //some code here
public:
    Konfiguration(QApplication*, MainWindow*);
    virtual ~Konfiguration();     

    public slots:
        void clearText();
//      void updateTextN(QString);
//      void updateTextM(QString);
};


//konfiguration.cpp

// use the mainwindow pointer to set Slot 

  //Set N, M in VerschiebeSpiel
 QObject::connect(editN,SIGNAL(textChanged(QString)),spielFenster,SLOT(setN(QString)));
 QObject::connect(editM,SIGNAL(textChanged(QString)),spielFenster,SLOT(setM(QString)));

So how can I open the Konfiguration Window via the Menu bar of Mainwindow but I can still use the Konfiguration to configure the MainWindow ?

Muss be simple for you guys, but quite hard for newbie :)

thx for your help

mrjj

@Yrandom

the circular includes problem can often be solved with a forward of the class

so instead of ( in the other class header)
#include <myclass>

you just
do

class MyClass; // this is a forward

and you are allowed to have
class Other {
MyClass * mc;

Since all the use of the Myclass functions, are in the CPP file, it works.

In the CPP file you then include the actual header.

Not sure i explained it good :(

Please see
http://stackoverflow.com/questions/625799/resolve-header-include-circular-dependencies

Yrandom

@mrjj
thx for the quick answer.

Now I got build successfull but when I start the Programm and klick on menubar set configuration
I got Windows disconnection and have to quit

here is what i Changed

///////////////////////////////
// in mainwindow.h
// mainclass mainwindow
#include <QMenuBar>
#include <QAction>

class Konfiguration; // this is the other class

using namespace std;

class MainWindow : public QMainWindow {
   Q_OBJECT
private:
Konfiguration *confi;
//code
}

//////////////////////////
//mainwindow.cpp
#include "mainwindow.h"
#include "Konfiguration.h"

 // Configuration Window
void MainWindow::openConfi(){
//
// try to add something like confi = new Konfiguration(&app,this) like in the main() is not working either.
//
    confi->show();
// Debugger stoppt at show()
}

// in Konfiguration.h
#include "MainWindow.h"

class Konfiguration : public QDialog{
    Q_OBJECT
    
private:
code
}