Augmenting objects on per instance basis

["Max van Rooij \(van Rooij Electronics Design & Software Engineering\)" <mvrooij@...>]

Title: Bericht

Dear all,

 

I'm new to Lua and very enthusiastic about it, especially in it's ability to interface with C. I've written a GUI in C and have given the users the ability to customize behaviours (such as mouse clicks) in Lua.

 

I've defined a so called "click-able" region as a struct in C. The user can create a region that's click-able in a lua script with a single line like this:

 

mywidget1 = widget.create(100,100,10,10) --create click-able region at (x,y) = 100,100 width 10 and height 10

 

By implementing the __index in C code, the user can write:

 

function mywidget1:leftclick

print("hurray! a left click!")

end

 

Now, the C code is capable to relate the clicked region to the right Lua object and a get a nice "hurray!" printed. Unfortunatly, if my user does:

 

mywidget1 = widget.create(100,100,10,10)

mywidget2 = widget.create(110,110,20,20)

 

function mywidget1:leftclick

print("left click widget 1")

end

 

function mywidget2:leftclick

print("left click widget 2")

end

 

I always get "left click widget 2". This is, because the widgets share the same method table, so the last definition simply overwrites all previous ones. How do I change my C code, so my users can have the above code working?

 

Thanks

 

Max