QProgressBar breaks with large values

Kekz

@Christian-Ehrlicher That was also one of my thoughts but I was hoping there would be a better way.
Is it possible to extends the QProgressBar class and override these methods and attributes?

Christian Ehrlicher

@Kekz said in QProgressBar breaks with large values:

Is it possible to extends the QProgressBar class and override these methods and attributes?

No and I don't see why it should be needed. If you need it derive from QProgressBar and do the scaling there but adding a /100 or similar before passing the values isn't worth the trouble imo.

Kekz

@Christian-Ehrlicher Deriving was what I meant, sry. ~~Then I will probably go that route and use 64-bit values, thanks for the help.~~
On second thought, that probably won't work. I will need to resort to scaling...

Pablo J. Rogina

@Kekz said in QProgressBar breaks with large values:

Is it possible to extends the QProgressBar class and override these methods and attributes?

Yes, it is.
The question could be: is it worth? rather than scale the values as @Christian-Ehrlicher suggested...

JonB

@Kekz
If it floats your boat, derive from QProgressBar and write your own setRange(), setValue() etc. new method overloads which accept a size_t or double or whatever. And that can do the division to do the "scaling" there, so your callers won't have to.

Kekz

@JonB
I was hoping to be able to also override the value, min and max attributes to force Qt to use 64-bit values, but that doesn't seem to work.
I'll have to scale the values down, it's an ugly solution but the only one that seems possible.

nagesh

@Kekz Internally

ProgressBar will display the percentage of steps that have been 
completed when you later give it the current step value. 

The percentage is calculated by dividing the progress
 (value() - minimum()) / (maximum() - minimum())

So you can set value min max as 0,SCALE_MAX always irrespective file size.
ui->fileProgressBar->setRange(0,SCALE_MAX );

void Controller::UpdateFileProgress( const size_t FileSize, const size_t value)

double ratio= static_cast<double>(value) / static_cast<double>(FileSize);
int scaledvalue =( ratio * SCALE_MAX );

JonB

@Kekz said in QProgressBar breaks with large values:

I was hoping to be able to also override the value, min and max attributes to force Qt to use 64-bit values, but that doesn't seem to work.

You cannot "override" variables, or the type of variables, in C++ (e.g. you cannot declare variables virtual). QProgressBar uses ints (32-bit) for these, and you cannot alter that.

I'll have to scale the values down, it's an ugly solution but the only one that seems possible.

I do not see this as even vaguely "ugly". QProgressBar works off a range of possible values something like -2,000,000,000 to +2,000,000,000, which is more than enough to cover the visible "steps" available on the bar, and that's what you must supply it with for min/max/value. Scaling the number from, say a float to an int seems fine to me, and you can add your own methods to your QProgressBar subclass to make this invisible to the outside world.

Kekz

@JonB I guess you are right, my concerns about loosing precision were unfounded since 2 billion steps will always be more than enough.
I will do as @nagesh (and many others) suggested and mark this as solved.

JonB

@Kekz
A 32-bit has 4 billion range. Your horizontal screen resolution is, say, 1,920 pixels. So 2 million bits available per pixel the user can see. I don't think losing precision will be an issue :)