Can userdate have references to lua objects?

[Tobias Käs <tobias.kaes@...>]

Is it possible for userdata to tell the GC it has a (native) reference to another userdata object, and so prevent the GC to collect it?

Here's an example how i thought to use it:

 

 

-- returns a 'bitmap' userdata

bmp = gfx.LoadBitmap("test.bmp")

 

-- returns a 'font' userdata which depends on the bitmap

-- should tell the gc it has a reference to 'bmp'

font = gfx.CreateFont(bmp)

 

-- removes the lua side reference of the bitmap

bmp = nil

 

-- must not collect the bitmap since 'font' has a reference

collectgarbage()

 

-- remove font reference

font = nil

 

-- is allowed to collect the font

-- its finalizer releases its reference to the bitmap

collectgarbage()

 

-- is now allowed to collect the bitmap

collectgarbage()