Low performance, timer and label.
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Hi, i have some problems with QTimer, and label. I wanna create a simple stopwatch, but the time is highly delayed, it's around 15% different, so 30s is equal to 35s.
Settext function is causing all the problems, and i need it to update the Ms label.
I am having a lot of bugs with QT, and one of them is it, i have two stopwatches, and one of them was working almost good (Very small percent of delay,almost 0), and the second one, was almost 35% of delay, horrible score.... The second one, is working on the same simple function, and i made it (It's a copy, with different variable name's).
I was trying to find the issue, why one of the timer, working with a copy of function, was doing that.
What's funny? When i just deleted the old TabWidget, and created new one (In general, i dont change any settings), now these two timers have the same delay of around 7-10%. I have no idea what's going on, and i have enough.If you can do something, cuz i have some bugs with my Qt, sometimes when i delete some objects, then when i press one button, the application crash, and i need to delete, and rebuild the project (It doesn't work if i just press the rebuild button, i lose a lot of time before i notice that).
Release version is a completely mess up, simple calculations are giving some totally unknown results, basicly 100% is broken, functions are giving stuff from nowhere.
If i switch to debug version, everything works good. Just the timers still have that low performance.
I dont know if i should download newer version, and what is causing these problems.
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@Loc888 said in Low performance, timer and label.:
I am having a lot of bugs with Qt
Don't blame the framework. We all did it at least once. It was never the framework's fault.
Can you post your current code?
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@Loc888 said in Low performance, timer and label.:
Give me back my wasted time
I could say the same here.
If you want help, a bit of humility and accepting the fact that there's a 99.9% chance the problem is in your code and not in Qt is a first step
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@Loc888 said in Low performance, timer and label.:
Give me back my wasted time
I could say the same here.
If you want help, a bit of humility and accepting the fact that there's a 99.9% chance the problem is in your code and not in Qt is a first step
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Can you try this basic example?
#include <QApplication> #include <QTimer> #include <QLabel> int main(int argc, char *argv[]) { QApplication a(argc, argv); QLabel mainWid; QTimer mainTimer; int counter = 0; QObject::connect(&mainTimer,&QTimer::timeout,[&mainWid,&counter]()->void{ mainWid.setText(QObject::tr("%1 sec").arg(++counter)); }); mainTimer.start(1000); mainWid.show(); return a.exec(); } -
Can you try this basic example?
#include <QApplication> #include <QTimer> #include <QLabel> int main(int argc, char *argv[]) { QApplication a(argc, argv); QLabel mainWid; QTimer mainTimer; int counter = 0; QObject::connect(&mainTimer,&QTimer::timeout,[&mainWid,&counter]()->void{ mainWid.setText(QObject::tr("%1 sec").arg(++counter)); }); mainTimer.start(1000); mainWid.show(); return a.exec(); } -
@Loc888 I tested it on my machine Qt 5.10 MSVC2013 x64 Win7. What version of Qt are you running?
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Then everything should work, you probably just have to enable C++11
- add
CONFIG += c++11in your.profile - re-run qmake
- add
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@VRonin It's working, but i need it in MS. It happens because text need to be updated fast, and it cause the problem. If i just run the timer, it's look's fine, but i need to show the time in label..
@Loc888 I think you need to be a bit more specific, with what is going on.
It's working, but i need it in MS. It happens because text need to be updated fast, and it cause the problem. If i just run the timer, it's look's fine, but i need to show the time in label..
Updating a QLabel's text shouldn't take seconds to update
to modify the code of @VRonin abit to display time and fast changes:
#include <QApplication> #include <QTimer> #include <QLabel> #include <QTime> int main(int argc, char *argv[]) { QApplication a(argc, argv); QLabel mainWid; QTimer mainTimer; QObject::connect(&mainTimer,&QTimer::timeout,[&mainWid]()->void{ mainWid.setText(QTime::currentTime().toString("hh.mm.ss.zz")); }); mainTimer.start(10); mainWid.show(); return a.exec(); } -
@Loc888 I think you need to be a bit more specific, with what is going on.
It's working, but i need it in MS. It happens because text need to be updated fast, and it cause the problem. If i just run the timer, it's look's fine, but i need to show the time in label..
Updating a QLabel's text shouldn't take seconds to update
to modify the code of @VRonin abit to display time and fast changes:
#include <QApplication> #include <QTimer> #include <QLabel> #include <QTime> int main(int argc, char *argv[]) { QApplication a(argc, argv); QLabel mainWid; QTimer mainTimer; QObject::connect(&mainTimer,&QTimer::timeout,[&mainWid]()->void{ mainWid.setText(QTime::currentTime().toString("hh.mm.ss.zz")); }); mainTimer.start(10); mainWid.show(); return a.exec(); } -
@J.Hilk I would like to use that, but i don't want current time, i want everything starting from 0.
@Loc888
this code examples are for the purpose of trouble shooting.
But it's easy enought to adapt.#include <QApplication> #include <QTimer> #include <QLabel> #include <QTime> #include <QElapsedTimer> int main(int argc, char *argv[]) { QApplication a(argc, argv); QLabel mainWid; QTimer mainTimer; QTime time(0,0); QElapsedTimer actualTimePassed; QObject::connect(&mainTimer,&QTimer::timeout,[&mainWid, &time, &actualTimePassed]()->void{ time = time.addMSecs(actualTimePassed.elapsed()); actualTimePassed.start(); mainWid.setText(time.toString("hh.mm.ss.zzz")); }); actualTimePassed.start(); mainTimer.start(10); mainWid.show(); return a.exec(); } -
@VRonin It's working, but i need it in MS. It happens because text need to be updated fast, and it cause the problem. If i just run the timer, it's look's fine, but i need to show the time in label..
@Loc888 said in Low performance, timer and label.:
it's working, but i need it in MS
Unfortunately this is platform dependant. Best you could do is:
#include <QApplication> #include <QTimer> #include <QLabel> int main(int argc, char *argv[]) { QApplication a(argc, argv); QLabel mainWid; QTimer mainTimer; mainTimer.setTimerType(Qt::PreciseTimer); unsigned int counter = 0; QObject::connect(&mainTimer,&QTimer::timeout,[&mainWid,&counter]()->void{ mainWid.setText(QObject::tr("%1 msec").arg(++counter)); mainWid.repaint(); }); mainTimer.start(1); mainWid.show(); return a.exec(); }Please note, from http://doc.qt.io/qt-5/qt.html#TimerType-enum:
Precise timers try to keep millisecond accuracy
try != will, unfortunately
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@Loc888 said in Low performance, timer and label.:
it's working, but i need it in MS
Unfortunately this is platform dependant. Best you could do is:
#include <QApplication> #include <QTimer> #include <QLabel> int main(int argc, char *argv[]) { QApplication a(argc, argv); QLabel mainWid; QTimer mainTimer; mainTimer.setTimerType(Qt::PreciseTimer); unsigned int counter = 0; QObject::connect(&mainTimer,&QTimer::timeout,[&mainWid,&counter]()->void{ mainWid.setText(QObject::tr("%1 msec").arg(++counter)); mainWid.repaint(); }); mainTimer.start(1); mainWid.show(); return a.exec(); }Please note, from http://doc.qt.io/qt-5/qt.html#TimerType-enum:
Precise timers try to keep millisecond accuracy
try != will, unfortunately
@VRonin Maybe i expressed wrong, but i don't want it in Ms (the total), so 5500 = 5,5s, i want that pattern "mm.ss.zzz" or "mm.ss.zz" , but i want it to start from 0, not from the current time. Is any way to force it? (In sec, ther is no delay when the method update the text).
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@Loc888
this code examples are for the purpose of trouble shooting.
But it's easy enought to adapt.#include <QApplication> #include <QTimer> #include <QLabel> #include <QTime> #include <QElapsedTimer> int main(int argc, char *argv[]) { QApplication a(argc, argv); QLabel mainWid; QTimer mainTimer; QTime time(0,0); QElapsedTimer actualTimePassed; QObject::connect(&mainTimer,&QTimer::timeout,[&mainWid, &time, &actualTimePassed]()->void{ time = time.addMSecs(actualTimePassed.elapsed()); actualTimePassed.start(); mainWid.setText(time.toString("hh.mm.ss.zzz")); }); actualTimePassed.start(); mainTimer.start(10); mainWid.show(); return a.exec(); }@J.Hilk Guys,i tried J.Hilk code,and it's not working how it should.
It doesnt help me, it's working, but if i compare the timer to my windows time, the difference is arround 10s (after 2min test), it's too mutch.
Why it's happening?
Ps. I tried with "setTimerType(Qt::PreciseTimer);", but still doesn't help...
????????
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My turn ;)
QLabel label; label.setGeometry(100,100,200,50); QTimer timer; QTime time; QObject::connect(&timer,&QTimer::timeout,[&time,&label](){ QTime elapsed=QTime::fromMSecsSinceStartOfDay(time.elapsed()); label.setText(elapsed.toString("mm:ss:zzz")); }); time.start(); timer.start(100); label.show(); -
My turn ;)
QLabel label; label.setGeometry(100,100,200,50); QTimer timer; QTime time; QObject::connect(&timer,&QTimer::timeout,[&time,&label](){ QTime elapsed=QTime::fromMSecsSinceStartOfDay(time.elapsed()); label.setText(elapsed.toString("mm:ss:zzz")); }); time.start(); timer.start(100); label.show();It seems you are the winner... Why it's working?
I thought it's working, because you set the delay to 100ms, but even if i change it to 1ms, still working 100%.
I don't understand why this is working,and the other timers including my, are all retarded... Why it's happening?And that's the text update method fault's, i tried to turn off the update, and just set the last result, and it's 100% accurate.
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I know by experience that to rely on a timer is all wrong.
You must rely on the system clock for good accuracy.And that's the text update method fault's, i tried to turn off the update, and just set the last result, and it's 100% accurate.
Refresh 1000 times per sec is a heavy task, it consumes about 20% cpu on my machine and serves nothing.
Timers use the event loop and if the computer is doing heavy tasks, timers triggers might be lost.
Rely on event loops for a counter is definitely a bad idea. -
I know by experience that to rely on a timer is all wrong.
You must rely on the system clock for good accuracy.And that's the text update method fault's, i tried to turn off the update, and just set the last result, and it's 100% accurate.
Refresh 1000 times per sec is a heavy task, it consumes about 20% cpu on my machine and serves nothing.
Timers use the event loop and if the computer is doing heavy tasks, timers triggers might be lost.
Rely on event loops for a counter is definitely a bad idea.@mpergand Ok, how i can use it with Start, Stop, and Reset button? Because i am trying to move your code to another project, and work with buttons, but when i start the timer, it doesn't do anything.. Still be on 00:00:000, i run it ones, and it start from the actual minutes and seconds, then i modified your code to force it start from 0, and i broke something, now nothing is working...
