Re: [Wxlua-users] Virtual method - Howto

[John L. <jla...@gm...>]

On 8/27/06, msh...@ya... <msh...@ya...> wrote:
>
> I am trying to make a easiest way to implement virtual method. Something like
> wxLuaPrintout of howto override HasPage() etc.. method, but actually I did not quite get it
> the how (as it touches some HasDerivedMethod()  and some tag definition which I do not
> have time to look at it yet). Is there a fast explanation and howto step, to do it?
>

It's fairly easy, but maybe not so obvious. The binding files (*.i)
just contain the functions as for any other class, don't be fooled by
wxLuaPrintout seemingly not having any functions, they are defined in
the base wxPrintout binding.

The c++ class has to implement the code to check to see if there is a
lua function overriding it. See modules/wxbind/src/wxlprint.cpp for
some examples. Note that we've decided to add a ref counted wxLuaState
to the c++ class and then have to override the constructor, see
bindings/wxwidgets/overrides.cpp wxLua_wxLuaPrintout_constructor
instead of trying to lookup what lua_State we're coming from on the
fly each time a function is called. Once inside the c++ function, see
any of the wxLuaPrintout functions, you handle the args and do
whatever is necessary then always call
SetCallBaseClassFunction(false), otherwise you'll get recursion, if
you call base_SOMEFUNCNAME() you always should get the base class
function.

If you can think of a way to automate this a little better that'd be
great. There is one change I've been meaning to make however, we need
a way to make naming wxLuaPrintout just wxPrintout in lua since the
lua code doesn't need to know or care that it's really a
wxLuaPrintout.

Hope this helps,
    John Labenski