SplashScreen stay on TaskManager

[QtA_]

@mrjj said in SplashScreen stay on TaskManager:

Oh. that way.
Well you dont have a MainWindow.
QApplication will close application when the last window is closed.
Not sure it knows about QSplashScreen.

But when you dont have any mainwindow/top level widgets, it keeps running.

You can make it exit calling quit() but its hard with just a QSplashScreen.

So as you see in tut 28. he does have Mainwindow also ?

yes the tutorial have windows application...
but I don't need it..

in fact my project is simple,...
I want to make a splashscreen with PNG transparency,..(without windows form)
so I don't know if this is the way to go for it..

I want to start with this,..and then,..add features...to be customized,.like time delay, fadein/fadeout, animated PNG etc...

[mrjj]

@QtA_
Ok, "(without windows form)" means with no borders or caption etc?

I think you can use splashscreen for this but not sure its really needed.

Will it be sort of a class others can use , as a super splashscreen thing or
what is the goal ?

Well you current issue can be fixed by calling apps quit() when you want the app to exit.
like 2 timers. one call close for splashscreen and other call quit()
but it all depends on how u want it to work.

[QtA_]

@mrjj said in SplashScreen stay on TaskManager:

@QtA_
Ok, "(without windows form)" means with no borders or caption etc?

I think you can use splashscreen for this but not sure its really needed.

Will it be sort of a class others can use , as a super splashscreen thing or
what is the goal ?

Well you current issue can be fixed by calling apps quit() when you want the app to exit.
like 2 timers. one call close for splashscreen and other call quit()
but it all depends on how u want it to work.

that's why I'm here :)

I'm a biginner with C++, so need to understand manything actually.
my english is also not very good, but its ok I think. :)

The goal should be something like this:

1. create an EXE allowing parameters to show splashscreen.

ex:
mysplash.exe "c:/my images/logo1.png" /d:3 /fi:1 /fo:1

wich:
/d = delay
/fi = fade in time delay
/fo = fade out time delay

then,...few version after,...allowing to execute splash with mutliple image running to make an animated splash with PNG files.. :)

[mrjj]

@QtA_
ahh, sort of fancy app loader. :)
well that is a fun project.

You english is fine. :)

That should be possible for a first project. Good luck and feel free to ask.

[QtA_]

@mrjj said in SplashScreen stay on TaskManager:

@QtA_
ahh, sort of fancy app loader. :)
well that is a fun project.

You english is fine. :)

That should be possible for a first project. Good luck and feel free to ask.

Thank you very much,..
I'm a fancy girl :)

return a.quit();

do not close the process,..do I miss something ?

[mrjj]

@QtA_
Hi
do you now have
return a.exec();
return a.quit();

?

it stays inside a.exec().

you can try
QTimer::singleShot(2500,&app,SLOT(quit()));
should kill it all after 2,5 secs.
U must keep return a.exec(); to use timers. Its drives the eventloop :)

[QtA_]

@mrjj said in SplashScreen stay on TaskManager:

@QtA_
Hi
do you now have
return a.exec();
return a.quit();

?

it stays inside a.exec().

yes

[mrjj]

@QtA_
You need to send it signal to quit.
Try
QTimer::singleShot(2500,&app,SLOT(quit()));
dont remove the exec() part.
its very important to use signals.

[QtA_]

nope,..:( still active.

#include <QApplication>
#include <QSplashScreen>
#include <QTimer>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    QSplashScreen *splash=new QSplashScreen;
    splash->setPixmap(QPixmap ("C:/Users/public/test/Logo.png"));
    splash->show();
    QTimer::singleShot(2500,splash,SLOT(close()));
    QTimer::singleShot(2500,splash,SLOT(quit()));

    return a.exec();
    return a.quit();

}

[mrjj]

@QtA_
You are asking it wrongly :)

QTimer::singleShot(2500,splash,SLOT(quit())); <<<< wrong object. should be &app

you are asking the timer to call quit() on splash, which splash dont have.

QTimer::singleShot(2500,&app,SLOT(quit()));

Update:
Also
The return statement will make it leave a function
so

return a.exec();
return a.quit(); <<< u can never, ever get here :)

[QtA_]

Thank you very much !! :)
so i've added:

QTimer::singleShot(2500,&a,SLOT(quit()));

and removed

return a.exec();

seem to work fine now :)

Question...

why do I need to put time delay on quit if already the time done ?
I mean,..

QTimer::singleShot(2500,&a,SLOT(quit()));

must be

QTimer::singleShot(0,&a,SLOT(quit()));

?

[mrjj]

@QtA_
Hi
Np.

Does it display long enough with
QTimer::singleShot(0,&a,SLOT(quit())); ?

Then its ok.

[QtA_]

ok ...I've change the close by the quit.
instead adding a new line. :)

Thanks again for all your help.
Angie xx

[mrjj]

@QtA_
Np. Have fun programming. :)

[Chris Kawa]

You don't need to force the app quit. It's not very flexible in the long run. By default Qt app quits automatically when a last window is closed. This is controlled in two places: on application level with setQuitOnLastWindowClosed (the default is true, so no need to change that). The other place is at the widget level with an attribute Qt::WA_QuitOnClose. This attribute is by default enabled for top level windows i.e. widgets with flag Qt::Window or Qt::Dialog except for certain types, including menus, tooltips and splashscreen.

Since a splashscreen is all you have you can just turn the attribute back on:

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    QSplashScreen *splash = new QSplashScreen;
    splash->setAttribute(Qt::WA_QuitOnClose);  // <-- the relevant line
    splash->setPixmap(QPixmap ("C:/Users/public/test/Logo.png"));
    splash->show();
    QTimer::singleShot(2500,splash,SLOT(close()));
    return a.exec();
}

Btw. Technically this code leaks memory as you never delete the splash instance. To keep it clean you have couple of options:

• manually delete the splash after the call to exec
• add WA_DeleteOnClose attribute to the splash
• (the easiest and recommended) just create the splash instance on the stack:

QSplashScreen splash;
splash.setAttribute(Qt::WA_QuitOnClose);
splash.setPixmap(QPixmap ("C:/Users/public/test/Logo.png"));
splash.show();
QTimer::singleShot(2500,&splash,SLOT(close()));

[mrjj]

@Chris-Kawa
Much better with WA_QuitOnClose, indeed. :)

Do you know if QSplashScreen can do anything special compared to a plain QWidget in terms
of her overall goal? ( sort of fancy launcher )

Im not sure if a custom widget is not more fun later when she wants animations and fade in/out effects etc. Of Course she can derive from QSplashScreen but I do wonder if it
give anything of benefit for this use case. ?

[QtA_]

Thank you guys,,...
it seem to work,..

however..many questions in my little brain..

splash name is my variable right ?
so may I redefine it many times ?

#include <QApplication>
#include <QSplashScreen>
#include <QTimer>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    QSplashScreen *splash = new QSplashScreen;
    splash->setAttribute(Qt::WA_QuitOnClose);  // <-- the relevant line
    splash->setPixmap(QPixmap ("C:/Users/public/test/Logo.png"));
    splash->show();
    QTimer::singleShot(2500,splash,SLOT(close()));
    
    splash->setPixmap(QPixmap ("C:/Users/public/test/Logo1.png"));
    splash->show();
    QTimer::singleShot(2500,splash,SLOT(close()));
    
    return a.exec();
}

seem it keep always the last image...

[Chris Kawa]

@mrjj QSplashScreen is pretty basic. It's not well suited for any sort of animations. The easiest route for that would be, indeed, a plain old widget and overriding its paintEvent. Deriving from QSplashScreen would just get in your way.

@QtA_ You're thinking in line, while what happens is event driven. This code QTimer::singleShot(2500,splash,SLOT(close())); doesn't "wait" for 2.5 seconds. It just schedules the slot to fire in 2.5 seconds and moves on immediately. So this:

splash->setPixmap(QPixmap ("C:/Users/public/test/Logo.png"));
splash->show();
QTimer::singleShot(2500,splash,SLOT(close()));
splash->setPixmap(QPixmap ("C:/Users/public/test/Logo1.png"));

is just the same as this:

splash->setPixmap(QPixmap ("C:/Users/public/test/Logo.png"));
splash->setPixmap(QPixmap ("C:/Users/public/test/Logo1.png"));
splash->show();
QTimer::singleShot(2500,splash,SLOT(close()));

To make it work like you want to you need to schedule the switch to happen some time later, e.g.

splash->setPixmap(QPixmap ("C:/Users/public/test/Logo.png")); //set initial image
QTimer::singleShot(1000, [&]{ splash->setPixmap(QPixmap ("C:/Users/public/test/Logo1.png")); }); //change it after a second
QTimer::singleShot(2000, [&]{ splash->setPixmap(QPixmap ("C:/Users/public/test/Logo2.png")); }); //change it again after 2 seconds etc.

splash->show();
QTimer::singleShot(2500,splash,SLOT(close()));

[QtA_]

ok,...that work great !
my PNG animation is now done.. :) thank you.

However,..there is few questions if you dont mind.
is the [&] mean to execute what is in the bracket ? {}

I understand what i'm doing...but I do not understand yet how, when and why to put sometime bracket, [] sometime <> sometime "" or {}
i'm a little lost on when to use it..
is there any tutorial who explain this syllabus ?
Thanks again for all your help :)

[mrjj]

@QtA_ said in SplashScreen stay on TaskManager:
Hi

is the [&] mean to execute what is in the bracket ? {}

Yes its a c++ lambda. Think of it as "in place" function.

QTimer::singleShot(1000, [&]
{
//this is the function body
splash->setPixmap(QPixmap ("C:/Users/public/test/Logo1.png"));
}
);

I understand what i'm doing...but I do not understand yet how, when and why to put sometime bracket, [] sometime <> sometime "" or {}

Oh,  there are many different uses, depending on context.
{ } is often used as a block.
if (something)  {
// line 1
// line 2
} 
--
void somefunc() {
}
-----------------------
[] is used with array or lists. 
(and also the lambda syntax)
int list[1000];
int num=list[1];
-----------------------
The <> is often seen with templates. Templates are special c++ thing that allows any type to be used. the compiler will generate the needed code for all used types.
std::vector<int> mylist; // list of ints.

So its hard to fully answer as its used in many contexts. So you better just ask :)