setStyle -> USER Objects leak

KIT2005

Re: Change the size of ">>" arrow when a QToolBar is too small

It is possible to change the size of the >> extension button in the Toolbar, by subclassing QProxyStyle as shown below.

virtual int MyProxyStyle::pixelMetric(PixelMetric pm, const QStyleOption* option, const QWidget* widget) const
{
if( pm == QStyle::PM_ToolBarExtensionExtent )
return XXX; // width for horizontal, height for vertical toolbars
return QProxyStyle::pixelMetric(pm, option, widget);
}

But setStyle() using MyProxyStyle increases the USER Objects which eventually leads to crash after many days of continuously creation and deletion of Toolbar.

Does setStyle() has memory leak?

SGaist

Hi,

How are you using your custom style ?
Why are you constantly deleting/creating that toolbar ?

mrjj

@KIT2005 said in setStyle -> USER Objects leak:

Does setStyle() has memory leak?

Well, on QWidgets:.setStyle, ownership is not transferred, so if you new the style each time you assign it, and never delete the last one, you will leak.

KIT2005

Hi,

I have many pages with different controls. One such control has the toolbar and so when I switch from one page to another having the control with toolbar, the USER objects increases.

During the creation of Toolbar I have used
MyProxyStyle *proxyStyle = new MyProxyStyle ();
if(proxyStyle )
setStyle(proxyStyle );

In the destructor, I have used
if(proxyStyle )
{
delete proxyStyle ;
proxyStyle = NULL;
}

I have concluded that by commenting the line setStyle() the USER objects are not increasing. So I am not sure if there is a leak with QT or i am doing something wrong

mrjj

@KIT2005
Hi
but is dtor called on each time you switch ?
also the code shown has a local style
MyProxyStyle *proxyStyle = ... // local

so in dtor
if(proxyStyle )
{
delete proxyStyle ;

what style is that ? seems not to be the one you new.

SGaist

Your if statement won't help, you are creating a local variable named proxyStyle so unless you run out of memory, it will alway be true as the allocation will succeed.

KIT2005

@mrjj
I am doing the page switch at regular interval and my dtor is also called everytime.

MyProxyStyle *proxyStyle = ../ is not local but a member variable. I typed the statement to show the creation part and its a typo error.

It is actually

proxyStyle = new MyProxyStyle ();
if(proxyStyle )
setStyle(proxyStyle );

KIT2005

@mrjj

Thanks for the hint"QWidgets:.setStyle, ownership is not transferred". It helped me fix the issue.

Solved setStyle -> USER Objects leak