[Panel-devel] Separate QGraphicsItems for applet border/background and content?

[Aaron J. Seigo]

On Friday 31 August 2007, Robert Knight wrote:
> > so contentSize is mis-named because ... it returns the size of the
> > contents?
>
> Let me try to clarify.  Items in a layout have an actual size and an
> 'ideal' size.  The actual size is returned by geometry().size() (
> QWidget also provides a size() method ).  The 'ideal' size is that
> returned by sizeHint() may differ from the actual size if there is not
> enough space available or excess space.

ok, so we have a couple of issues here.

the simpler and less central one to this issue relates to whether layouts 
expand on their own or remain constrained to their container. we went for the 
latter as it makes a number of things easier, including actually 
approximating resolution independant layouts.

the more important one is "what is contentSize supposed to return". and 
indeed, it is supposed to return the actual size.

the reason it defaults to the sizeHint() of the layout is that the layout 
actually fits to the size of the applet, so we can't meaningfully ask for its 
size.. we simply ask for the optimal size it suggests.

for applets that don't use a single top-level layout, then they need to 
reimplement contentSize to do as you expect.

we could make the base implementation of contentSize (which must remain 
virtual) not return layout()->sizeHint() but some other value. of course, 
what that value would be is a good question, since the layout adapts to the 
container not the other way around. personally, i think it is returning the 
correct thing given the original goal. =)

anyways:

> What I did temporarily to make things work is to make contentSize()
> non-virtual and add a virtual 'contentSizeHint()' method to allow the
> applets to provide a hint as to what size they would like their
> content to be - and the logical extension of this is to add
> minimumContentSize() , maximumContentSize() etc. methods as you
> suggest.  This however makes the API inconsistent as you would use
> minimumContentSize() , maximumContentSize() in the main Applet class
> and then minimumSize() , maximumSize() , sizeHint() etc. in the
> applet's child widgets.

this is perhaps just one more reason to s,content,applet, in the method names 
to make the reason for the difference clear.

and really the *Content*() methods (or *Applet*() methods, as the case may be) 
only get used internally in Applet and reimplemented by applets that need to. 
it'll be a pretty hidden inconsistency. not perfection, indeed, but other 
options seems either more convoluted or simply more fragile.

-- 
Aaron J. Seigo
humru othro a kohnu se
GPG Fingerprint: 8B8B 2209 0C6F 7C47 B1EA  EE75 D6B7 2EB1 A7F1 DB43

KDE core developer sponsored by Trolltech
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