[paragui-dev] small fixes and template question

[Martin Bickel]

Hi,

here are some small improvements for Paragui, which should be
self-explanatory. I've also replaced the type-cast in
pglistboxbaseitem.cpp to use RuntimeTypeInformation to make it at least
return a NULL-Pointer if it goes wrong. I think we can assume to have
RTTI available, can't we?

But the design should definitly be fixed in that area. I tried changing
PG_ListBoxItem constructor to only accept PG_ListBox* as parent, but
this breaks PG_DropDown::AddItem , because it constructs PG_ListBoxItem
with a  PG_DropDown as parent. I think this is a major design error,
because the current C-style cast will result in complely unpredictable
behaviour in that case.



And I have a question about the signal definition, which I've been
wondering about since I've first seen them. What is the purpose of a
templated signal definition like this:

class Something {

template<class datatype = PG_Pointer> class SignalButtonClick : public 
PG_Signal1<PG_Button*, datatype> {};
SignalButtonClick<> sigClick;

What's the difference to a non-templated definition like:

typedef PG_Signal1<PG_Button*, PG_Pointer> SignalButtonClick;
SignalButtonClick sigClick;


This first one is obviously a member template, but while I can see the
purpose of member template functions,  I've got real problems
understanding data member templates.


Martin

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