[wx-discuss] wxTNG: backends

[Stefan Csomor]

Hi 

> I guess it'll be the pImpl design as already used in some 
> wxWidgets classes. But how will deriving classes and 
> overriding functionality work when the basic work is being 
> done by an object of a different class than the one you're 
> deriving from? We do away with the normal use of virtual 
> functions to override functionality as hinted at in another thread?

if we take the pImpls used in wxMac as an example for discussion, there
two different groups, some are already determined at compile time
(quickdraw and quartz dcs), some only at runtime (eg the textcontrol)
which implementation will be used. This decision which of a group of
implementation is used is right now done in the Create method directly,
but could also be deferred to a factory of some kind. 

Now there are two points in which you could imagine an application
wanting to extend, one would eg be to have a better native text control
implementation, in which case the native implementation would be
subclassed and the default factory would have to be informed about this,
if wanted also the 'standard' textcontrol would use the new
implementation. This would most probably be the rare case. On the other
you might want to have the 'front-end' wxTextControl subclassed in order
to accomplish extensions in a generic ie not platform dependent way (you
still might have access to the underlying HWND etc. however)

Best,

Stefan

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