Implement lua __index and __newindex for capi objects about awesome HOT 4 CLOSED

[11:30] <psychon> I wonder if we can come up with something that is "transparent" to uses in rc.lua
[11:31] <Elv1313> psychon: yes, but it will require being able to set custom metatables for client
[11:31] <Elv1313> that way we can use __index to hijack .border_width and __newindex for the setter. Then it wont break the API and just work
[11:31] <normalra> Exactly.
[11:31] <psychon> hm... might be a good idea to have
[11:32] <psychon> well, rather than setting the metatable, it might be easier to be able to set handlers for __index and __newindex for "property misses" (when the C code doesn't know how to handle things)
[11:32] <Elv1313> I tried to implement that the other day, but ran out of time without much results (I don't know the luac API that well)
[11:32] <Elv1313> psychon: yes, that would work
[11:35] <psychon> "just" requires patching luaA_class_newindex() and luaA_class_index()
[11:35] <psychon> instead of calling newindex_miss_property, they'd need to call into some lua function (that somehow lua must be able to set earlier...)
[11:38] <Elv1313> psychon: if you take care of the C side, I will implement the handlers. I already have the code in Radical to do just that
[11:38] <Elv1313> it also emulate :set_foo(x) -> object.foo = x
[11:41] <Elv1313> psychon: do you want me to create an issue for that?
[11:41] <psychon> yeah, feel free
[11:41] <psychon> and we need to come up with some API for lua to set the handlers
[11:41] <psychon> does it make sense to have them object-specific? or is it ok to have it just per-class?
[11:43] <Elv1313> I guess client, tag, screen, drawable, key and drawin should have the same API
[11:43] <psychon> looking forward to your feature requests which includes explanations on how the API might look like :-P
[11:47] <phryk> Do things like wibox or the widgets use lua classes and I just find lua confusing or are they implemented as just a bunch of functions?
[11:48] <Elv1313> psychon: https://github.com/awesomeWM/awesome/issues/163
[11:48] <psychon> phryk: lua doesn't have a built-in concept of a "class"
[11:48] <psychon> Elv1313: thanks, will take a look on saturday

-- For experiments with the error handling:
local check_errors = false

if check_errors then
    drawin.set_index_miss_handler(function(...) error("Nope") end)
    drawin.set_newindex_miss_handler(function(...) error("Nope") end)
else
    drawin.set_index_miss_handler(function(...) print("index miss", ...) return print, 42 end)
    drawin.set_newindex_miss_handler(function(...) print("newindex miss", ...) return 42 end)
end

d = drawin({})
print("getting d.foo")
print(d.foo)
print("setting d.bar = 7")
d.bar = 7
-- This would call nil
if not check_errors then
    print("calling foobar")
    print(d:foobar("calling foobar"))
end