[Panel-devel] Problem with caching applet backgrounds

[Peter Penz]

Hi Thomas,

On Sunday 29 July 2007 17:20:59 Thomas Georgiou wrote:
> On Sunday 29 July 2007 01:02:03 am Aaron J. Seigo wrote:
> > * there's no need to new() pixmaps. it leads to memory leaks, such as how
> > you're leaking backgroundPixmap.
>
> Wouldn't the pixmap be deleted after the function returns though?

I think Aaron refers to the line:

[A] QPixmap* backgroundPixmap = new QPixmap(leftWidth + contentWidth + 
rightWidth, topHeight + contentHeight + bottomHeight);

which should be written like:

[B] QPixmap backgroundPixmap(leftWidth + contentWidth + rightWidth, topHeight 
+ contentHeight + bottomHeight);

In the case of [A] the pixmap is allocated on the heap and not deleted until 
you invoke 'delete backgroundPixmap' (which seems is not done).

In the case of [B] the pixmap is allocated on the stack [1] and destructed 
automatically as soon as the end of the scope is reached.

I found an interesting discussion about stack vs. heap here :-)
http://discuss.joelonsoftware.com/default.asp?joel.3.103986.24

Best regards,
Peter

[1] To be more exact: The Pixmap instance will be allocated on the stack, but 
the data of the pixmap will be allocated on the heap and freed as soon as the 
destructor gets invoked.

> And should i store it as a pointer or by value in the d-pointer?
>
> Thomas Georgiou
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