---- On Wed, 07 Nov 2018 13:00:50 +0100 luigi scarso <luigi.sca...@gmail.com>
wrote ----
>
>
> On Wed, Nov 7, 2018 at 12:18 PM Marcel Krüger <t...@2krueger.de> wrote:
> Hi,
>
> I recently discovered that the Lua wrapper of mplib registers all callbacks
> globally
> such that creating multiple mplib instances with different callbacks
> breaks.
>
>
> why not this ?
> \directlua{ local current_instance local custom_find_file =
> custom_find_file or {} local mp_find_file_driver = function(name, mode,
> type) print("I am ",current_instance) if custom_find_file[current_instance]
> then return custom_find_file[current_instance](name, mode, type) else
> return "unregistered" end end custom_find_file['mp1'] =
> function(name, mode, type) return name end custom_find_file['mp2'] =
> function(name, mode, type) if name == 'cmr10' then print'This should not
> happen' end return name end
> local mp1 = mplib.new{ find_file = mp_find_file_driver }
> local mp2 = mplib.new{ find_file = mp_find_file_driver
> } current_instance = "mp1" mp1:execute[[ input cmr10;
> ]]
> current_instance = "mp2" mp2:execute[[ input cmr10;
> ]]
>
> } \bye
That's similar to the workaround I'm using right now, but it seems odd:
The callbacks are given as in the initializer table of a single instance,
so you do not expect them to affect other instances. Especially this means that
if anyone
uses "short-living" MPLib instances, this person will probably not expect this
behaviour
and just pass the find_file method directly.
This means that every user of "long-living" MPLib instances has to fear that
every
called library might change this global state.
If this happens, there does not even seem to be a way to change it back, so the
safest
approach would be to call mplib.new and create and destroy a temporary instance
every time `:execute` or `:finish` is called.
So if this is the intended behaviour, IMO a note should be added to
the documentation. Especially because every non-function entry in
the initializer only affects this instance.
But I still think it should be changed: The current behaviour seems unintuitive
and inconsistant.
Also manually keeping track of the current instance seems at least odd if mplib
can access this information anyway.
Additionally the change would make the Lua API of mplib more similar to the C
API.
Best regards
Marcel Krüger
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